Electronic apparatus, content reproducing method, and content decoding method

[Object] To promptly decode and reproduce content of any encoding formats.[Solving Means] If a TV (1) judges that it cannot decode content to be viewed by a user, the TV (1) asks another apparatus such as a game apparatus (3) or PC (4) whether it can decode the content via a high-speed data line (150) capable of performing bidirectional IP communication in expanded HDMI and transmits the content and decoding request command thereof to an apparatus which has answered that it can perform decoding, via the high-speed data line (150). The game apparatus (3) or the PC (4) which has received the decoding request decodes the content and transmits the decoded content as a baseline signal to the TV (1) via TMDS channels in expanded HDMI so that the content is reproduced.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/JP2007/071664 filed Nov. 7, 2007, published on May 15, 2008 as WO 2008/056718 A1, which claims priority from Japanese Patent Application No. JP 2006-301486 filed in the Japanese Patent Office on Nov. 7, 2006, Japanese Patent Application No. JP 2007-050426 filed in the Japanese Patent Office on Feb. 28, 2007, and Japanese Patent Application No. JP 2007 166918 filed in the Japanese Patent Office on Jun. 25, 2007.

TECHNICAL FIELD

The present invention relates to an electronic apparatus connected to another electronic apparatus and capable of reproducing content, a content reproducing method, and a content decoding method in the electronic apparatus.

BACKGROUND ART

In recent years, there have been structured systems in which electronic apparatuses such as PCs (Personal Computers), television apparatuses, and other AV (Audio/Visual) equipment are interconnected to transmit broadcast signals and various content on a network or the Internet. However, since there are a wide variety of encoding formats of the broadcast signals and the content on the network or the Internet, there are video content, audio content, and Web content encoded in an encoding format incapable of being decoded, depending on electronic apparatuses.

Regarding such problem, the following Patent Document 1 describes a technique in which a terminal apparatus preliminarily notifies a server apparatus of information indicating formats and bit rates that can be decoded by the terminal apparatus, and the server apparatus converts formats and bit rates in accordance with the information to transmit content to a client apparatus.

Further, the following Patent Document 2 also describes a technique in which a video reproducing apparatus transmits attribute information regarding its own data reproducing ability or storage capacity to a video transmitting apparatus, and the video transmitting apparatus encodes content based on the attribute information to transmit the content to a client apparatus.Patent Document 1: Japanese Patent Application Laid-open No. Hei 9-284567 (paragraphs (0040) to (0046), etc.)Patent Document 2: Japanese Patent Application Laid-open No. 2001-358799 (paragraph (0006), etc.)Patent Document 3: Japanese Patent Application Laid-open No. 2005-57714Patent Document 4: Japanese Patent Application Laid-open No. 2006-19948

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

However, in the technique described in Patent Document 1 or Patent document 2, reproduction desired by a user cannot be performed promptly, which causes waiting time for the user because it takes time to convert the format of the content in the server apparatus or the video transmitting apparatus and to decode the converted content in the terminal apparatus or the video reproducing apparatus.

In view of the above-mentioned circumstances, it is an object of the present invention to provide an electronic apparatus capable of decoding and reproducing content of any encoding formats promptly, a content reproducing method, and content decoding method in the electronic apparatus.

Means for Solving the Problem

To solve the problem mentioned above, according to a principle aspect of the present invention, there is provided an electronic apparatus connected to another electronic apparatus including a first communication means for transmitting content encoded in an encoding format incapable of being decoded by the electronic apparatus and a decoding request signal that requests decoding of the content, a second communication means for receiving the content decoded in the another electronic apparatus in accordance with the request signal, as a baseband signal, and a reproduction means for reproducing the received content.

Here, the content refers to moving image content, still image content, audio content, text content, Web content, and the like. The acquisition source of the content is not specifically limited, and any content is applicable such as broadcasted content, content acquired from a recording medium, content produced by a user him/herself, for example. Further, examples of the encoding format include MPEG-1 (Moving Picture Experts Group phase 1), MPEG-2, MPEG-4, and MPEG-4 AVC (Advanced Video Coding) for moving images, JPEG (Joint Photographic Experts Group) and GIF (Graphic Interchange Format) for still images, and MP3 (MPEG-1 Audio Layer-3), AAC (MPEG-2(4) Audio AAC), and ATRAC (Adaptive TRansform Acoustic Coding) for audio. In addition, the electronic apparatus includes a television apparatus, a PC, a DVD player, an HDD (Hard Disk Drive) recorder, AV equipment such as an AV amplifier and a game apparatus. The first communication means and second communication means may have a single transmission line or separate transmission lines. Note that “reproducing” indicates that a video signal and an audio signal of content are made to be ready for being output, and includes not only a case where the electronic apparatus has an output device such as a display unit and a speaker, but a case of transmitting the video signal and the audio signal to a display unit and a speaker which are externally connected to the electronic apparatus.

With this structure, it is possible to decode and reproduce content of any encoding formats, because even content incapable of being decoded by one electronic apparatus can be decoded by another electronic apparatus. Thus, a user can view desired content without purchasing a new apparatus compatible with the decoding, resulting in improved convenience. Further, by receiving the content as the decoded baseband signal, time for decoding after format conversion is less required than the case of transmitting content incapable of being decoded to another apparatus to cause the another apparatus to convert the encoding format. Therefore, in response to a reproducing request for content from the user, it is possible to start reproducing promptly regardless of a decoding ability of the electronic apparatus.

In the electronic apparatus, the first communication means may transmit the decoding request signal and the content via a first transmission line having a first transmission speed, and the second communication means may receive the decoded content via a second transmission line having a second transmission speed faster than the first transmission speed.

Here, the first transmission line includes the Ethernet (Registered Trademark), a USB (Universal Serial Bus), and IEEE 1394, for example, and the second transmission line includes an HDMI, a DVI (Digital Visual Interface), a Display Port, and a UDI (Unified Display Interface), for example. The first transmission speed is about 100 Mbps to 500 Mbps, for example, and the second transmission speed is about 5 Gbps to 10 Gbps, for example, but not limited to those ranges. In the case of using the HDMI for the second transmission line, the electronic apparatus serves as a sink apparatus, and the another electronic apparatus serves as a source apparatus. Further, the first transmission line and the second transmission line may be accommodated to a single cable, and the first communication means and the second communication means may be constituted as a single terminal having respective pin connectors for the first transmission line and the second transmission line. For example, as the first transmission line, a line expanded such that high-speed bidirectional communication such as IP communication becomes possible like the Ethernet (Registered Trademark) by making a pair of an HPD (Hot Plug Detect) line and a reserved line in a conventional HDMI to carry out transmission of differential signals may be employed. Further, as the second transmission line, TMDS (Transition Minimized Differential Signaling) channels may be employed.

With this structure, because a relatively small-volume signal of the encoded content and the decoding request signal are transmitted via the first transmission line and a large-volume baseband signal of the decoded content is received via the second transmission line, it is possible to efficiently transmit/receive content and promptly reproduce even content incapable of being decoded without waiting time for a user.

In the electronic apparatus, the another electronic apparatus includes a plurality of other apparatuses, and the first communication means may include means for transmitting, to each of the plurality of other electronic apparatuses, a query signal that queries processing time required for the decoding of the content, means for receiving, from the plurality of other electronic apparatuses, response signals each of which responds with the processing time to the query signal, and means for transmitting the decoding request signal to one of the plurality of other electronic apparatuses that is capable of decoding the content in a minimum processing time, in accordance with each of the response signals.

Accordingly, by transmitting the decoding request signal to one electronic apparatus capable of decoding the content in the shortest processing time, it is possible to decode and reproduce the content more efficiently even in the case where there are a plurality of other apparatuses capable of decoding the content.

In the electronic apparatus, the another electronic apparatus may be connected to a server apparatus storing software for decoding the content, and the first communication means may include means for transmitting a query signal that queries whether the decoding of the content is possible to the another electronic apparatus, means for receiving a response signal that responds as to whether the decoding of the content is possible from the another electronic apparatus, and means for transmitting to the another apparatus, if the response signal that responds that the decoding is impossible is received, a receiving request signal that requests reception of the software from the server apparatus and the decoding request signal that requests the decoding by using the received software.

Accordingly, it is possible to reproduce any content by the electronic apparatus even in the case where the another electronic apparatus also cannot decode the content, by causing the another apparatus to receive the software from the server apparatus and to decode the content using the software.

According to another aspect of the present invention, there is provided an electronic apparatus connected to another electronic apparatus including a first communication means for receiving content encoded in an encoding format incapable of being decoded by the another electronic apparatus and a decoding request signal that requests decoding of the content from the another electronic apparatus, a decoding means for decoding the content in accordance with the decoding request signal, and a second communication means for transmitting the decoded content as a baseband signal to the another electronic apparatus.

With this structure, it is possible to cause the another electronic apparatus to reproduce any content even in the case where the another electronic apparatus cannot decode the content, by decoding the content in response to the request from the another apparatus and transmitting the content as the baseband signal.

In the electronic apparatus, the first communication means may receive the decoding request signal and the content via a first transmission line having a first transmission speed, and the second communication means may transmit the decoded content via a second transmission line having a second transmission speed faster than the first transmission speed.

Accordingly, it is possible to efficiently carry out the process from decoding to reproduction of the content with the another electronic apparatus, by providing separately the transmission line used for receiving the encoded content and the decoding request signal of the content and the transmission line used for transmitting the decoded content.

In the electronic apparatus, the first communication means may include means for receiving a query signal that queries whether the decoding of the content is possible and processing time required for the decoding of the content from the another electronic apparatus, and means for transmitting a response signal that responds as to whether the decoding is possible and responds with the processing time to the another electronic apparatus.

Accordingly, it is possible to perform the process to reproduction of the content more efficiently even in the case where there are electronic apparatuses other than the electronic apparatus which are capable of decoding the content in accordance with the request from the another electronic apparatus, by causing the another electronic apparatus as the source of the decoding request to select an electronic apparatus capable of performing the decoding in the shortest processing time.

The electronic apparatus may further include a judging means for judging whether the decoding of the content is possible or not, and a third communication means for receiving, if it is judged that the decoding is impossible, the software for decoding the content from a server apparatus storing the software. The decoding means may decode the content using the received software.

Accordingly, it is possible to cause the another electronic apparatus to reproduce any content even in the case where the electronic apparatus cannot decode the content, by receiving the software and carrying out decoding using the software. Note that the third communication means is the Ethernet (Registered Trademark), for example.

According to another aspect of the present invention, there is provided a content reproducing method in an electronic apparatus connected to another electronic apparatus including transmitting the content encoded in an encoding format incapable of being decoded by the electronic apparatus and a decoding request signal that requests decoding of the content, receiving the content decoded in the another electronic apparatus in accordance with the request signal as a baseband signal, and reproducing the received content.

According to further aspect of the present invention, there is provided a content decoding method in an electronic apparatus connected to another electronic apparatus including receiving the content encoded in an encoding format incapable of being decoded by the another electronic apparatus and a decoding request signal that requests decoding of the content from the another electronic apparatus, decoding the content in accordance with the decoding request signal, and transmitting the decoded content as a baseband signal to the another electronic apparatus.

Effect of the Invention

As described above, according to the present invention, it is possible to promptly decode and reproduce content of any encoding formats.

BEST MODES FOR CARRYING OUT THE INVENTION

First, a description will be given on a conventional communication system (image transmission system) that can perform bidirectional IP communication at high speed, while retaining compatibility with a communication interface such as HDMI.

In recent years, HDMI® is prevailing as a communication interface for transmitting at high speed a digital television signal, i.e., pixel data of uncompressed (baseband) images, and audio data accompanied by the images, for example, from a DVD recorder, a set-top box, and other AV sources to a television set, a projector, and other displays.

For HDMI®, the HDMI specifications stipulate a TMDS (Transition Minimized Differential Signaling) channel unidirectionally transmitting at high speed pixel data and audio data from an HDMI® source to an HDMI® sink, a CEC line (Consumer Electronics Control Line) for performing bidirectional communication between an HDMI® source and an HDMI® sink, and the like.

FIG. 1is a diagram showing a structure of a typical image transmission system.

For example, as shown inFIG. 1, pixel data and audio data can be transmitted at high speed by connecting a digital television set11and an AV amplifier12by an HDMI® cable13conforming with HDMI®.

The digital television set11, the AV amplifier12, and a reproducing apparatus14are installed in a living room of a user's house at the left side inFIG. 1. The digital television set11and the AV amplifier12, and the AV amplifier12and reproducing apparatus14are connected by an HDMI® cable13and an HDMI® cable15.

Further, a hub16is installed in the living room, and the digital television set11and reproducing apparatus14are connected to the hub16by a LAN (Local Area Network) cable17and a LAN cable1. In addition, in a bedroom to the right of the living room in the figure, a digital television set19is installed, and the digital television set19is connected to the hub16via a LAN cable20.

For example, in reproducing content recorded in the reproducing apparatus14and displaying an image on the digital television set11, the reproducing apparatus14decodes pixel data and audio data for reproducing the content, and supplies the obtained uncompressed pixel data and audio data to the digital television set11via the HDMI® cable15, the AV amplifier12, and the HDMI® cable13. Based on the pixel data and audio data supplied from the reproducing apparatus14, the digital television set11displays images and outputs sounds.

Further, in reproducing content recorded in the reproducing apparatus14and displaying images on the digital television set11and the digital television set19at the same time, the reproducing apparatus14supplies compressed pixel data and audio data for reproducing the content to the digital television set11via the LAN cable18, the hub16, and the LAN cable17, and to the digital television set19via the LAN cable18, the hub16, and the LAN cable20.

Further, the digital television set11and the digital television set19decode the pixel data and audio data supplied from the reproducing apparatus14, and display images and output sounds based on the obtained uncompressed pixel data and audio data.

Further, in a case where the digital television set11receives pixel data and audio data for reproducing a program over television broadcasting, when the received audio data is audio data of, for example, 5.1-channel surround audio data and the digital television set11cannot decode the received audio data, the digital television set11converts the audio data into an optical signal and transmits the optical signal to the AV amplifier12.

The AV amplifier12receives the optical signal transmitted from the digital television set11, photoelectrically converts the optical signal, and decodes the audio data thus obtained. In addition, the AV amplifier12amplifies the decoded uncompressed audio data when necessary, and reproduces sounds at surround speakers connected to the AV amplifier12. In this manner, the digital television set11reproduces a 5.1-channel surround program by decoding the received pixel data and displaying images by using the decoded pixel data and by outputting sounds at the AV amplifier12based on the audio data supplied to the AV amplifier12.

FIG. 2is a diagram showing a structure of an image transmission system according to an embodiment to which the present invention is applied.

The image transmission system is constituted of a digital television set31, an amplifier32, a reproducing apparatus33, and a digital television set34. The digital television set31and amplifier32, and the amplifier32and reproducing apparatus33are connected by an HDMI® cable35and an HDMI® cable36in conformity with HDMI®, respectively. The digital television set31and the digital television set34are connected by a LAN cable37for LAN such as Ethernet (Registered Trademark).

In the example shown inFIG. 2, the digital television set31, the amplifier32, and the reproducing apparatus33are installed in a living room of a user's house at the left inFIG. 2, and the digital television set34is installed in a bedroom to the right of the living room.

The reproducing apparatus33is formed of, for example, a DVD player, a hard disc recorder, or the like, decodes pixel data and audio data for reproducing content, and supplies the uncompressed pixel data and audio data thus obtained to the amplifier32via the HDMI® cable36.

The amplifier32is formed of, for example, an AV amplifier, is supplied with pixel data and audio data from the reproducing apparatus33, and amplifies the supplied audio data when necessary. Further, the amplifier32supplies the audio data amplified when necessary and the pixel data, which are supplied from the reproducing apparatus33, to the digital television set31via the HDMI® cable35. Based on the pixel data and audio data supplied from the amplifier32, the digital television set31displays images and outputs sounds to reproduce the content.

In addition, the digital television set31and the amplifier32can perform bidirectional communication such as IP communication at high speed by using the HDMI® cable35, and the amplifier32and the reproducing apparatus33can also perform bidirectional communication such as IP communication at high speed by using the HDMI® cable36.

Namely, for example, the reproducing apparatus33can transmit compressed pixel data and audio data as data in conformity with IP to the amplifier32via the HDMI® cable36through IP communication with the amplifier32, and the amplifier32can receive the compressed pixel data and audio data transmitted from the reproducing apparatus33.

In addition, the amplifier32can transmit compressed pixel data and audio data as data in conformity with IP to the digital television set31via the HDMI® cable35through IP communication with the digital television set31, and the digital television set31can receive the compressed pixel data and audio data transmitted from the amplifier32.

The digital television set31can therefore transmit the received pixel data and audio data to the digital television set34via the LAN cable37. Further, the digital television set31decodes the received pixel data and audio data, and based on the obtained uncompressed pixel data and audio data, displays images and outputs sounds to reproduce the content.

The digital television set34receives and decodes the pixel data and audio data transmitted from the digital television set31via the LAN cable37, and based on the uncompressed pixel data and audio data obtained by decoding, displays images and outputs sounds to reproduce the content. In this manner, the same or different content can be reproduced at the same time at the digital television set31and the digital television set34.

Further, when the digital television set31receives pixel data and audio data for reproducing a program as content over television broadcasting, and if the received audio data is audio data of, for example, 5.1-channel surround audio data and the digital television set31cannot decode the received audio data, the digital television set31transmits the received audio data to the amplifier32via the HDMI® cable35by IP communication with the amplifier32.

The amplifier32receives and decodes the audio data transmitted from the digital television set31, and amplifies the decoded audio data when necessary. Then, the amplifier32reproduces 5.1-channel surround sounds from speakers (not shown) connected to the amplifier32.

The digital television set31transmits the audio data to the amplifier32via the HDMI® cable35, decodes the received pixel data, and based on the pixel data obtained by decoding, displays images to reproduce the program.

In this manner, in the image transmission system shown inFIG. 2, the electronic apparatus such as the digital television set31, amplifier32, and reproducing apparatus33connected by the HDMI® cable35and the HDMI® cable36can perform IP communication at high speed by using the HDMI® cables, and therefore it is not necessary to use LAN cable corresponding to the LAN cable17shown inFIG. 1.

Further, the digital television set31and the digital television set34are connected by the LAN cable37, and the digital television set31can transmit data received from the reproducing apparatus33via the HDMI® cable36, the amplifier32, and the HDMI® cable35, to the digital television set34via the LAN cable37. It is therefore unnecessary to use the LAN cable and the electronic apparatus corresponding to the LAN cable18and the hub16shown inFIG. 1.

In the conventional image transmission system shown inFIG. 1, cables of different types are required depending on transmission/reception data and communication methods so that wirings of cables interconnecting electronic apparatuses are complicated. In contrast, in the image transmission system shown inFIG. 2, electronic apparatuses connected by the HDMI® cable can perform high speed bidirectional communication such as IP communication so that connection between electronic apparatuses can be simplified. Namely, complicated conventional wirings of cables connecting electronic apparatuses can be made simpler.

Next,FIG. 3shows an example of a structure of an HDMI® source and an HDMI® sink which are respectively built in electronic apparatuses connected by an HDMI® cable, e.g., an HDMI® source provided in the amplifier32shown inFIG. 2and an HDMI® sink provided in the digital television set31.

An HDMI® source71and an HDMI® sink72are connected by one HDMI® cable35, and the HDMI® source71and the HDMI® sink72can perform bidirectional IP communication at high speed by using the HDMI® cable35while retaining compatibility with current HDMI®.

In an effective video period (hereinafter, arbitrarily referred to also as an active video period) which is a period from one vertical synchronization signal to the next vertical synchronization signal subtracting horizontal blanking periods and a vertical blanking period, the HDMI® source71transmits differential signals corresponding to pixel data of an uncompressed image of one screen, unidirectionally to the HDMI® sink72via a plurality of channels. In the horizontal blanking period or vertical blanking period, the HDMI® source transmits differential signals corresponding to at least audio data and control data accompanied by the image, other auxiliary data and the like, unidirectionally to the HDMI® sink72via a plurality of channels.

That is, the HDMI® source71has a transmitter81. The transmitter81converts, for example, pixel data of an uncompressed image into corresponding differential signals, and transmits unidirectionally and serially the differential signals to the HDMI® sink72via three TMDS channels #0, #1, and #2of the HDMI® cable35.

Further, the transmitter81converts audio data accompanied by uncompressed images, necessary control data, other auxiliary data and the like, into Corresponding differential signals, and transmits unidirectionally and serially the converted differential signals to the HDMI® sink72connected via the HDMI® cable35by using three TMDS channels #0, #1, and #2.

Further, the transmitter81transmits a pixel clock synchronizing with the pixel data to be transmitted via the three TMDS channels #0, #1, and #2, to the HDMI® sink72connected to the HDMI® cable35, via a TMDS clock channel. Pixel data of 10 bits is transmitted via one TMDS channel #i (i=0, 1, and 2) during one pixel clock.

The HDMI® sink72receives the differential signals corresponding to the pixel data unidirectionally transmitted from the HDMI® source71via the plurality of channels during the active video period, and receives the differential signals corresponding to the audio data and control data unidirectionally transmitted from the HDMI® source71via the plurality of channels during the horizontal blanking period or vertical blanking period.

That is, the HDMI® sink72has a receiver82. The receiver82receives the differential signals corresponding to the pixel data and the differential signals corresponding to the audio data and control data unidirectionally transmitted from the HDMI® source71connected to the HDMI® cable35via the TMDS channels #0, #1, and #2, synchronously with the pixel clock transmitted also from the HDMI® source71via the TMDS clock channel.

The transmission channels of the HDMI® system constituted of the HDMI® source71and HDMI® sink72include a DDC (Display Data Channel)83and a transmission channel called a CEC line84, in addition to the three TMDS channels #0to #2as transmission channels for unidirectionally and serially transmitting the pixel data and audio data from the HDMI® source71to the HDMI® sink72synchronously with the pixel clock and the TMDS clock channel as a transmission channel for transmitting the pixel clock.

The DDC83is constituted of two signal lines (not shown) contained in the HDMI® cable35, and is used for the HDMI® source71to read E-EDID (Enhanced Extended Display Identification Data) from the HDMI® sink72connected to the HDMI® source71via the HDMI® cable35.

That is, in addition to the receiver82, the HDMI® sink72has an EDIDROM (EDID ROM (Read Only Memory))85storing E-EDID representative of information on the settings and performance of the HDMI® sink72itself. The HDMI® source71reads via DDC83E-EDID stored in EDIDROM85of the HDMI® sink72, from the HDMI® sink72connected to the HDMI® source71via the HDMI® cable35, and based on E-EDID, recognizes the settings and performance of the HDMI® sink72, i.e., for example, an image format (profile) capable of being processed by the HDMI® sink72(an electronic apparatus possessing the HDMI® sink72) such as RGB (Red, Green, Blue), YCbCr 4:4:4 and YCbCr 4:2:2.

Although not shown, similar to the HDMI® sink72, the HDMI® source71can also store E-EDID and transmit E-EDID to the HDMI® sink72when necessary.

The CEC line84is constituted of one signal line (not shown) contained in the HDMI® cable35, and is used for bidirectional communication of the control data between the HDMI® source71and the HDMI® sink72.

Further, the HDMI® source71and the HDMI® sink72can perform bidirectional IP communication by transmitting a frame in conformity with IEEE (Institute of Electrical and Electronics Engineers) 802.3 to the HDMI® sink72and the HDMI® source71, respectively, via DDC83or CEC line84.

The HDMI® cable35contains also a signal line86connected to a pin called Hot Plug Detect. Using this signal line86, the HDMI® source71and the HDMI® sink72can detect a connection of a new electronic apparatus, i.e., the HDMI® sink72or the HDMI® source71, respectively.

Next,FIG. 4andFIG. 5show the pin assignment of a connector (not shown) mounted on the HDMI® source71or the HDMI® sink72to be connected to the HDMI® cable35.

It should be noted that inFIG. 4andFIG. 5, a pin number for identifying each pin of the connector is written in the left column (PIN column), and a name of a signal assigned to each pin identified by the pin number written in the left column at the same row is written in the right column (Signal Assignment column).

FIG. 4shows the assignment of pins of a connector called Type-A of HDMI®.

Two signal lines being for transmitting differential signals TMDS Data#i+ and TMDS Data#i− of a TMDS channel #i are connected to pins (pin numbers1,4, and7) assigned to TMDS Data#i+ and pins (pin numbers3,6, and9) assigned to TMDS Data#i−.

Further, the CEC line84for transmitting a CEC signal of control data is connected to a pin having a pin number of13, and a pin having a pin number14is a reserved pin. If bidirectional IP communication can be performed by using this reserved pin, compatibility with current HDMI® can be retained. In order for differential signals to be transmitted by using the CEC line84and a signal line to be connected to the pin having the pin number14, the signal line to be connected to the pin having the pin number14and the CEC line84are wired as a differential twist pair and shielded and grounded to a ground line of the CEC line84and DDC83to be connected to a pin having a pin number17.

Further, a signal line for transmitting an SDA (Serial Data) signal such as E-EDID is connected to a pin having a pin number16, and a signal line for transmitting an SCL (Serial Clock) signal as a clock signal to be used for transmission/reception synchronization of the SDA signal is connected to a pin having a pin number15. DDC83shown inFIG. 3is constituted of the signal line for transmitting the SDA signal and the signal line for transmitting the SCL signal.

In addition, similarly to the CEC line84and the signal line to be connected to the pin having the pin number14, the signal line for transmitting the SDA signal and the signal line for transmitting the SCL signal are wired as a differential twist pair and shielded and grounded to a ground line to be connected to the pin having the pin number17, in order for differential signals to be transmitted.

Further, the signal line86for transmitting a signal for detecting connection of a new electronic apparatus is connected to a pin having a pin number19.

FIG. 5shows the assignment of pins of a connector called Type-C or mini-type of HDMI®.

Two signal lines being differential signal lines for transmitting differential signals TMDS Data#i+ and TMDS Data#i− of a TMDS channel #i are connected to pins (pin numbers2,5, and8) assigned to TMDS Data#i+ and pins (pin numbers3,6, and9) assigned to TMDS Data#i−.

Further, the CEC line84for transmitting a CEC signal is connected to a pin having a pin number of14, and a pin having a pin number17is a reserved pin. Similarly to Type-A, the signal line to be connected to the pin having the pin number17and the CEC line84are wired as a differential twist pair and shielded and grounded to the ground line of the CEC line84and DDC83to be connected to a pin having a pin number13.

In addition, a signal line for transmitting an SDA signal is connected to a pin having a pin number16, and a signal line for transmitting an SCL signal is connected to a pin having a pin number15. Similarly to Type-A, the signal line for transmitting the SDA signal and the signal line for transmitting the SCL signal are wired as a differential twist pair and shielded and grounded to a ground line to be connected to the pin having the pin number13, in order for differential signals to be transmitted. The signal line86for transmitting a signal for detecting connection of a new electronic apparatus is connected to a pin having a pin number19.

Next,FIG. 6is a diagram showing the structure of the HDMI® source71and the HDMI® sink72for performing IP communication by half duplex communication using the CEC line84and the signal line connected to the reserved pin of the HDMI® connector. Note thatFIG. 6shows an example of the structure of a part regarding half duplex communication of the HDMI® source71and HDMI® sink72. In FIG.6, parts corresponding to those shown inFIG. 3are represented by identical symbols, and the description thereof is omitted as appropriate.

The HDMI® source71is constituted of the transmitter81, a switching control unit121, and a timing control unit122. In addition, the transmitter81is provided with a converting unit131, a decoding unit132, and a switch133.

Supplied to the converting unit131is Tx data to be transmitted from the HDMI® source71to the HDMI® sink72by bidirectional IP communication between the HDMI® source71and HDMI® sink72. For example, Tx data is compressed pixel data and audio data and the like.

The converting unit131is constituted of, e.g., a differential amplifier, and converts the supplied Tx data into differential signals having two partial signals. Further, the converting unit131transmits the differential signals obtained by conversion to the receiver82via the CEC line84and a signal line141connected to a reserved pin of a connector (not shown) provided in the transceiver81. Namely, the converting unit131supplies one partial signal constituting the differential signals obtained by conversion to the switch133via the CEC line84, more specifically, via the signal line that is provided in the transmitter81and connected to the CEC line84of the HDMI® cable35, and also supplies the other partial signal constituting the differential signals to the receiver82via the signal line141, more specifically, via the signal line that is provided in the transmitter81and connected to the signal line141of the HDMI® cable35and via the signal line141.

The decoding unit132is constituted of, e.g., a differential amplifier whose input terminals are connected to the CEC line84and signal line141. Under control of the timing control unit122, the decoding unit132receives differential signals transmitted from the receiver82via the CEC line84and signal line141, i.e., the differential signals constituted of the partial signal on the CEC line84and the partial signal on the signal line141, and decodes the differential signals to output original Rx data. Here, Rx data refers to data transmitted from the HDMI® sink72to the HDMI® source71by bidirectional IP communication between the HDMI® source71and the HDMI® sink72, and includes a command for requesting transmission of pixel data and audio data or the like, for example.

At a timing when data is transmitted, the switch133is supplied with the CEC signal from the HDMI® source71or the partial signal constituting the differential signals corresponding to Tx data from the converting unit131, and at a timing when data is received, the switch133is supplied with the CEC signal from the receiver82or the partial signal constituting the differential signals corresponding to Rx data from the receiver82. Under control of the switching control unit121, the switch133selectively outputs the CEC signal from the HDMI® source71, the CEC signal from the receiver82, the partial signal constituting the differential signals corresponding to Tx data, or the partial signal constituting the differential signals corresponding to Rx data.

Namely, the switch133selects either the CEC signal supplied from HDMI® source71or the partial signal supplied from the converting unit131, at a timing when the HDMI® source71transmits data to the HDMI® sink72, and transmits the selected CEC signal or partial signal to the receiver82via the CEC line84.

Further, the switch133receives either the CEC signal transmitted from the receiver82via the CEC line84or the partial signal of the differential signals corresponding to Rx data, at a timing when the HDMI® source71receives data transmitted from the HDMI® sink72, and supplies the received CEC signal or partial signal to the HDMI® source71or the decoding unit132.

The switching control unit121controls the switch133to change over the switch133to make the switch select one of the signals supplied to the switch133. The timing control unit122controls a reception timing of differential signals at the decoding unit132.

Further, the HDMI® sink72is constituted of the receiver82, a timing control unit123, and a switching control unit124. In addition, the receiver82has a converting unit134, a switch135, and a decoding unit136.

The converting unit134is constituted of, e.g., a differential amplifier, and supplied with Rx data. Under control of the timing control unit123, the converting unit134converts the supplied Rx data into differential signals having two partial signals, and transmits the signals obtained by conversion to the transmitter81via the CEC line84and the signal line141. Namely, the converting unit134supplies one partial signal constituting the differential signals obtained by conversion to the switch135via the CEC line84, more specifically, via the signal line provided in the receiver82and connected to the CEC line84of the HDMI® cable35, and also supplies the other partial signal constituting the differential signals to the transmitter81via the signal line141, more specifically, via the signal line provided in the transmitter81and connected to the signal line141of the HDMI® cable35.

At a timing when data is received, the switch135is supplied with the CEC signal from the transmitter81or the partial signal constituting the differential signals corresponding to Tx data from the transmitter81, and at a timing when data is transmitted, the switch135is supplied with the partial signal constituting the differential signals corresponding to Rx data from the converting unit134or the CEC signal from the HDMI® sink72. Under control of the switching control unit124, the switch135selectively outputs the CEC signal from the transmitter81, the CEC signal from the HDMI® sink72, the partial signal constituting the differential signals corresponding to Tx data, or the partial signal constituting the differential signals corresponding to Rx data.

Namely, the switch135selects either the CEC signal supplied from HDMI® sink72or the partial signal supplied from the converting unit134, at a timing when the HDMI® sink72transmits data to the HDMI® source71, and transmits the selected CEC signal or the partial signal to the transmitter81via the CEC line84.

Further, the switch135receives either the CEC signal transmitted from the transmitter81via the CEC line84or the partial signal of the differential signals corresponding to Tx data, at a timing when the HDMI® sink72receives data transmitted from the HDMI® source71, and supplies the received CEC signal or the partial signal to the HDMI® sink72or the decoding unit136.

The decoding unit136is constituted of, e.g., a differential amplifier whose input terminals are connected to the CEC line84and the signal line141. The decoding unit136receives differential signals transmitted from the transmitter81via the CEC line84and the signal line141, i.e., the differential signals constituted of the partial signal on the CEC line84and the partial signal on the signal line141, and decodes the differential signals to output original Tx data.

The switching control unit124controls the switch135to change over the switch135to make the switch135select one of the signals supplied to the switch135. The timing control unit123controls a transmission timing of differential signals at the converting unit134.

Further, the HDMI® source71and HDMI® sink72are structured as shown in, e.g.,FIG. 7, in a case that the HDMI® source71and HDMI® sink72perform IP communication by full duplex communication using the CEC line84and the signal line141connected to the reserved pin, and using the signal line for transmitting the SDA signal and the signal line for transmitting the SCL signal. Note that inFIG. 7, elements corresponding to those shown inFIG. 6are represented by identical symbols, and the description thereof is omitted as appropriate.

The HDMI® source71is constituted of a transmitter81, a switching control unit121, and a switching control unit171. The transmitter81has a converting unit131, a switch133, a switch181, a switch182, and a decoding unit183.

At a timing when data is transmitted, the switch181is supplied with the SDA signal from the HDMI® source71, and at a timing when data is received, the switch is supplied with the SDA signal from the receiver82or the partial signal constituting the differential signals corresponding to Rx data from the receiver82. Under control of the switching control unit171, the switch181selectively outputs the SDA signal from the HDMI® source71, the SDA signal from the receiver82or the partial signal constituting the differential signals corresponding to Rx data.

Namely, at a timing when the HDMI® source71receives data transmitted from the HDMI® sink72, the switch181receives the SDA signal transmitted from the receiver82via an SDA line191which is the signal line for transmitting the SDA signal or the partial signal of the differential signals corresponding to Rx data, and supplies the received SDA signal or the partial signal to the HDMI® source71or the decoding unit183.

Further, at a timing when the HDMI® source71transmits data to the HDMI® sink72, the switch181transmits the SDA signal supplied from the HDMI® source71, to the receiver82via the SDA line191, or transmits no signal to the receiver82.

At a timing when data is transmitted, the switch182is supplied with the SCL signal from the HDMI® source71, and at a timing when data is received, the switch182is supplied with the partial signal constituting the differential signals corresponding to Rx data from the receiver82. Under control of the switching control unit171, the switch182selectively outputs either the SCL signal or the partial signal constituting the differential signals corresponding to Rx data.

Namely, at a timing when the HDMI® source71receives data transmitted from the HDMI® sink72, the switch182receives the partial signal of the differential signals corresponding to Rx data transmitted from the receiver82via an SCL line192which is a signal line for transmitting the SCL signal, and supplies the received partial signal to the decoding unit183, or receives no signal.

Further, at a timing when the HDMI® source71transmits data to the HDMI® sink72, the switch182transmits the SCL signal supplied from the HDMI® source71, to the receiver82via the SCL line192, or transmits no signal to the receiver.

The decoding unit183is constituted of, e.g., a differential amplifier whose input terminals are connected to the SDA line191and the SCL line192. The decoding unit183receives differential signals transmitted from the receiver82via the SDA line191and SCL line192, i.e., the differential signals constituted of the partial signal on the SDA line191and the partial signal on the SCL line192, and decodes the differential signals to output original Rx data.

The switching control unit171controls the switch181and the switch182to change over the switch181and the switch182to make the switch181and the switch182select ones of the signals supplied to the switches.

In addition, the HDMI® sink72is constituted of a receiver82, a switching control unit124, and a switching control unit172. Further, the receiver82has a switch135, a decoding unit136, a converting unit184, a switch185, and a switch186.

The converting unit184is constituted of, e.g., a differential amplifier, and supplied with Rx data. The converting unit184converts the supplied Rx data into differential signals constituted of two partial signals, and transmits the differential signals obtained by conversion to the transmitter81via the SDA line191and the SCL line192. Namely, the converting unit184transmits one partial signal constituting the differential signals obtained by conversion to the transmitter81via the switch185and also supplies the other partial signal constituting the differential signals to the transmitter81via the switch186.

At a timing when data is transmitted, the switch185is supplied with the partial signal constituting the differential signals corresponding to Rx data from the converting unit184or the SDA signal from the HDMI® sink72, and at a timing when data is received, the switch is supplied with the SDA signal from the transmitter81. Under control of the switching control unit172, the switch185selectively outputs the SDA signal from the HDMI® sink72, the SDA signal from the transmitter81or the partial signal constituting the differential signals corresponding to Rx data.

Namely, at a timing when the HDMI® sink72receives data transmitted from the HDMI® source71, the switch185receives the SDA signal transmitted from the transmitter81via the SDA line191, and supplies the received SDA signal to the HDMI® sink72, or receives no signal.

Further, at a timing when the HDMI® sink72transmits data to the HDMI® source71, the switch185transmits the SDA signal supplied from the HDMI® sink72or the partial signal supplied from the converting unit184to the transmitter81via the SDA line191.

At a timing when data is transmitted, the switch186is supplied with the partial signal constituting the differential signals corresponding to Rx data from the converting unit184, and at a timing when data is received, the switch186is supplied with the SCL signal from the transmitter81. Under control of the switching control unit172, the switch186selectively outputs either the partial signal constituting the differential signals corresponding to Rx data or the SCL signal.

Namely, at a timing when the HDMI® sink72receives data transmitted from the HDMI® source71, the switch186receives the SCL signal transmitted from the transmitter81via the SCL line192, and supplies the received SCL signal to the HDMI® sink72or received no signal.

Further, at a timing when the HDMI® sink72transmits data to the HDMI® source71, the switch186transmits the partial signal supplied from the converting unit184to the transmitter81via the SCL line192or transmits no signal.

The switching control unit172controls the switch185and the switch186to change over the switch185and the switch186to make the switch185and the switch186select ones of the signals supplied to the switches.

Incidentally, when the HDMI® source71and the HDMI® sink72perform IP communication, whether half duplex communication or full duplex communication is possible depends on each structure of the HDMI® source71and the HDMI® sink72. Therefore, by referring to E-EDID received from the HDMI® sink72, the HDMI® source71judges to perform half duplex communication, full duplex communication, or bidirectional communication through transfer of the CEC signal.

E-EDID received by the HDMI® source71is constituted of a basic block and an expansion block such as shown inFIG. 8.

Data defined by the E-EDID1.3 specifications expressed by “E-EDID1.3 Basic Structure” is disposed at the start of the basic block of E-EDID, followed by timing information for retaining compatibility with conventional EDID expressed by “Preferred timing” and timing information different from “Preferred timing” for retaining compatibility with conventional EDID expressed by “2nd timing”.

Sequentially disposed in the basic block following “2nd timing” are information representative of a display device name expressed by “Monitor NAME” and information representative of the number of pixels capable of being displayed at aspect ratios of 4:3 and 16:9 expressed by “Monitor Range Limits”.

Whereas, at the start of the expansion block, information on right/left speakers represented by “Speaker Allocation” is disposed, followed by: data describing information on an image size, a frame rate, interlace or progressive capable of being displayed, and data describing an aspect ratio, expressed by “VIDEO SHORT”; data describing information on an audio codec method capable of being reproduced, a sampling frequency, a cut-off band, a codec bit number and the like, expressed by “AUDIO SHORT”; and information on right/left speaker expressed by “Speaker Allocation” sequentially in this order recited.

Sequentially disposed in the expansion block following “Speaker allocation” are data custom-defined for each maker expressed by “Vender Specific”, timing information expressed by “3rd timing” for retaining compatibility with conventional EDID, and timing information expressed by “4th timing” for retaining compatibility with conventional EDID.

Data expressed by “Vender Specific” has a data structure shown inFIG. 9. Namely, the data expressed by “Vender Specific” is provided with O-th to N-th blocks each having one byte.

Disposed in the 0-th block at the start of data expressed by “Vender Specific” is information representative of a header indicating the data area of the data “Vender Specific” expressed by “Vendor-Specific tag code (=3) and information representative of a length of the data “Vender Specific” expressed by “Length (=N)”.

Disposed in the first to third blocks is information on a number “0x000C03” registered for HDMI® and expressed by “24 bit IEEE Registration Identifier (0x000C03) LSB first”. Disposed in the fourth and fifth blocks is information representative of physical addresses of 24 bit sink apparatus represented by “A”, “B”, “C”, and “D”, respectively.

Disposed in the sixth block are: a flag indicating a function supported by each sink apparatus expressed by “Supports-AI”; information for designating the numbers of bits per pixel expressed by “DC-48 bit”, “DC-36 bit” and “DC-30 bit”, respectively; a flag indicating whether each sink apparatus can transmit an image of YCbCr 4:4:4, expressed by “DC-Y444”; and a flag indicating whether each sink apparatus can match a dual DVI (Digital Visual Interface), expressed by “DVI-Dual”.

Disposed in the seventh block is information representative of the highest frequency of a pixel clock of TMDS expressed by “Max-TMDS-Clock”. Disposed in the eighth block are a flag indicating presence/absence of delay information of video and audio signals expressed by “Latency, a full duplex flag indicating whether full duplex communication is possible, expressed by “Full Duplex”, and a half duplex flag indicating whether half duplex communication is possible, expressed by “Half Duplex”.

For example, the set full duplex flag (e.g., set to “1”) indicates that the HDMI® sink72has a function of performing full duplex communication, i.e., the HDMI® sink72has the structure shown inFIG. 7, whereas the reset full duplex flag (e.g., set to “0”) indicates that the HDMI® sink72does not have a function of performing full duplex communication.

Similarly, the set half duplex flag (e.g., set to “1”) indicates that the HDMI® sink72has a function of performing half duplex communication, i.e., the HDMI® sink72has the structure shown inFIG. 6, whereas the reset half duplex flag (e.g., set to “0”) indicates that the HDMI® sink72does not have a function of performing half duplex communication.

In the ninth block of data expressed by “Vender Specific”, delay time data of a progressive image expressed by “Video Latency” is disposed, and in the tenth block, delay time data of sounds accompanied by the progressive image expressed by “Audio Latency” is disposed. Further, in the eleventh block, delay time data of an interlayer image expressed by “Interlaced Video Latency” is disposed, and in the twelfth block, delay time data of sounds accompanied by the interlace image expressed by “Interlaced Audio Latency” is disposed.

Based on the full duplex flag and half duplex flag contained in E-EDID received from the HDMI® sink72, the HDMI® source71judges to perform the half duplex communication, full duplex communication, or bidirectional communication through transfer of the CEC signal, and performs bidirectional communication with the HDMI® sink72in accordance with the judged results.

For example, if the HDMI® source71has the structure shown inFIG. 6, the HDMI® source71can perform half duplex communication with the HDMI® sink72shown inFIG. 6, but cannot perform half duplex communication with the HDMI® sink72shown inFIG. 7.

Therefore, when the power of the electronic apparatus mounting the HDMI® source71is turned on, the HDMI® source71starts a communication process to perform bidirectional communication corresponding to the function possessed by the HDMI® sink72connected to the HDMI® source71.

Hereinafter, with reference to the flowchart shown inFIG. 10, description will be made on a communication process to be executed by the HDMI® source71shown inFIG. 6.

At Step S11the HDMI® source71judges whether a new electronic apparatus is connected to the HDMI® source71. For example, the HDMI® source71judges whether the new electronic apparatus mounting the HDMI® sink72is connected or not, in accordance with an amplitude of a voltage applied to the pin which is called “Hot Plug Detect” and connected to the signal line86.

If it is judged at Step S11that the new electronic apparatus is not connected, communication is not performed to thereafter terminate the communication process.

Whereas, if it is judged at Step S11that the new electronic apparatus is connected, then at Step S12the switching control unit121controls the switch133to change over the switch133to select the CEC signal from the HDMI® source71when data is transmitted and the CEC signal from the receiver82when data is received.

At Step S13the HDMI® source71receives E-EDID transmitted from the HDMI® sink72via DDC83. Namely, when a connection of the HDMI® source71is detected, the HDMI® sink72reads E-EDID from EDIDROM85and transmits the read E-EDID to the HDMI® source71via DDC83, so that the HDMI® source71receives E_EDID transmitted from the HDMI® sink72.

At Step S14the HDMI® source71judges whether it is possible to perform half duplex communication with the HDMI® sink72. Namely, the HDMI® source71refers to E-EDID received from the HDMI® sink72and judges whether the half duplex flag “Half Duplex” shown inFIG. 9is set, and if the half duplex flag is set, for example, the HDMI® source71judges that it is possible to perform bidirectional IP communication by a half duplex communication method, i.e., half duplex communication.

If it is judged at Step S14that half duplex communication is possible, at Step S15the HDMI® source71transmits a signal to the effect that IP communication by a half duplex communication method is performed using the CEC line84and signal line141, as channel information representative of a channel to be used for bidirectional communication, to the receiver82via the switch133and the CEC line84.

Namely, if the half duplex flag is set, the HDMI® source71can know that the HDMI® sink72has the structure shown inFIG. 6and that it is possible to perform half duplex communication using the CEC line84and signal line141, thus the HDMI® source71transmits the channel information to the HDMI® sink72to notify to the effect that half duplex communication is performed.

At Step S16the switching control unit121controls the switch133to change over the switch133to select the differential signals corresponding to Tx data from the converting unit131when data is transmitted and the differential signals corresponding to Rx data from the receiver82when data is received.

At Step S17each component of the HDMI® source71performs bidirectional IP communication with the HDMI® sink72by the half duplex communication method to thereafter terminate the communication process. Namely, when data is transmitted, the converting unit131converts Tx data supplied from the HDMI® source71into differential signals, and supplies one partial signal constituting the differential signals obtained by conversion to the switch133and the other partial signal to the receiver82via the signal line141. The switch133transmits the partial signal supplied from the converting unit131to the receiver82via the CEC line84. In this manner, the differential signals corresponding to Tx data are transmitted from the HDMI® source71to the HDMI® sink72.

When data is received, the decoding unit132receives differential signals corresponding to Rx data transmitted from the receiver82. Namely, the switch133receives the partial signal of the differential signals corresponding to Rx data transmitted from the receiver82via the CEC line84, and supplies the received partial signal to the decoding unit132. Under control of the timing control unit122, the decoding unit132decodes the differential signals constituted of the partial signal supplied from the switch133and the partial signal supplied from the receiver82via the signal line141to the original Rx data and output the original Rx data to the HDMI® source71.

In this manner, the HDMI® source71transfers various data such as control data, pixel data and audio data with the HDMI® sink72.

If it is judged at Step S14that half duplex communication is not possible, at Step S18each component of the HDMI® source71performs bidirectional communication with the HDMI® sink72through transmission/reception of the CEC signal to thereafter terminate the communication process.

Namely, when data is transmitted, the HDMI® source71transmits the CEC signal to the receiver82via the switch133and CEC line84, and when data is received, the HDMI® source71receives the CEC signal transmitted from the receiver82via the switch133and CEC line84to transfer control data with the HDMI® sink72.

In this manner, the HDMI® source71refers to the half duplex flag and performs half duplex communication with the HDMI® sink72capable of half duplex communication by using the CEC line84and signal line141.

As described above, high speed bidirectional communication can be performed while retaining compatibility with conventional HDMI®, by selecting transmission data and reception data by changing over the switch133and performing half duplex communication, i.e., IP communication by a half duplex communication method, with the HDMI® sink72by using the CEC line84and signal line141.

Further, similar to the HDMI® source71, the HDMI® sink72starts a communication process when the power of the electronic apparatus mounting the HDMI® sink72is turned on, and performs bidirectional communication with the HDMI® source71.

Hereinafter, with reference to the flowchart ofFIG. 11, description will be made on a communication process to be executed by the HDMI® sink72shown inFIG. 6.

At Step S41the HDMI® sink72judges whether a new electronic apparatus is connected to the HDMI® sink72. For example, the HDMI® sink72judges whether the new electronic apparatus mounting the HDMI® source71is connected or not, in accordance with an amplitude of a voltage applied to the pin which is called “Hot Plug Detect” and connected to the signal line86.

If it is judged at Step S41that the new electronic apparatus is not connected, communication is not performed to thereafter terminate the communication process.

On the other hand, if it is judged at Step S41that the new electronic apparatus is connected, then at Step S42the switching control unit124controls the switch135to change over the switch135to select the CEC signal from the HDMI® sink72when data is transmitted and the CEC signal from the transmitter81when data is received.

At Step S43the HDMI® sink72reads E-EDID from EDIDROM85, and transmits the read E-EDID to the HDMI® source71via DDC83.

At Step S44the HDMI® sink72judges whether channel information transmitted from the HDMI® source71is received.

Namely, channel information representative of a bidirectional communication channel is transmitted from the HDMI® source71in accordance with the functions possessed by the HDMI® source71and HDMI® sink72. For example, if the HDMI® source71has the structure shown inFIG. 6, the HDMI® source71and HDMI® sink72can perform half duplex communication using the CEC line84and signal line141. Therefore, the channel information to the effect that IP communication is performed using the CEC line84and signal line141is transmitted from the HDMI® source71to the HDMI® sink72. The HDMI® sink72judges that the channel information is received, after the channel information transmitted from the HDMI® source71via the switch135and CEC line84.

On the other hand, if the HDMI® source71does not have the half duplex communication function, the channel information is not transmitted from the HDMI® source71to the HDMI® sink72so that the HDMI® sink72judges that the channel information is not received.

If it is judged at Step S44that the channel information is received, the process advances to Step S45whereat the switching control unit124controls the switch135to change over the switch135to select the differential signals corresponding to Rx data from the converting unit134when data is transmitted and the differential signals corresponding to Tx data from the transmitter81when data is received.

At Step S46each component of the HDMI® sink72performs bidirectional IP communication with the HDMI® source71by the half duplex communication method to thereafter terminate the communication process. Namely, when data is transmitted, under control of the timing control unit123, the converting unit134converts Rx data supplied from the HDMI® sink72into differential signals, and supplies one partial signal constituting the differential signals obtained by conversion to the switch135and the other partial signal to the transmitter81via the signal line141. The switch135transmits the partial signal supplied from the converting unit134to the transmitter81via the CEC line84. In this manner, the differential signals corresponding to Rx data are transmitted from the HDMI® sink72to the HDMI® source71.

When data is received, the decoding unit136receives differential signals corresponding to Tx data transmitted from the transmitter81. Namely, the switch135receives the partial signal of the differential signals corresponding to Tx data transmitted from the transmitter81via the CEC line84, and supplies the received partial signal to the decoding unit136. The decoding unit136decodes the differential signals constituted of the partial signal supplied from the switch135and the partial signal supplied from the transmitter81via the signal line141to the original Tx data and output the original Tx data to the HDMI® sink72.

In this manner, the HDMI® sink72transfers various data such as control data, pixel data and audio data with the HDMI® source71.

If it is judged at Step S44that the channel information is not received, at Step S47each component of the HDMI® sink72performs bidirectional communication with the HDMI® source71through transmission/reception of the CEC signal to thereafter terminate the communication process.

Namely, when data is transmitted, the HDMI® sink72transmits the CEC signal to the transmitter81via the switch135and the CEC line84, and when data is received, the HDMI® sink72receives the CEC signal transmitted from the transmitter81via the switch135and CEC line84to transfer control data with the HDMI® source71.

In this manner, when the channel information is received, the HDMI® sink72performs half duplex communication with the HDMI® sink72by using the CEC line84and signal line141.

As described above, high speed bidirectional communication can be performed while retaining compatibility with conventional HDMI®, by performing half duplex communication using the CEC line84and signal line141between the HDMI® sink72and HDMI® source71by changing over the switch135to select transmission data and reception data.

Further, if the HDMI® source71has the structure shown inFIG. 7, in the communication process the HDMI® source71judges from the full duplex flag contained in E-EDID whether the HDMI® sink72has a full duplex communication function, and performs bidirectional communication in accordance with the judged result.

With reference to the flowchart shown inFIG. 12, description will be made on a communication process to be executed by the HDMI® source71shown inFIG. 7.

At Step S71the HDMI® source71judges whether a new electronic apparatus is connected to the HDMI® source71. If it is judged at Step S71that the new electronic apparatus is not connected, communication is not performed to thereafter terminate the communication process.

Whereas, if it is judged at Step S71that the new electronic apparatus is connected, then at Step S72the switching control unit171controls the switches181and182to change over the switches181and182to make the switch181select the SDA signal from the HDMI® source71and make the switch182select the SCL signal from the HDMI® source71, when data is transmitted and to make the switch181select the SDA signal from the HDMI® source71when data is received.

At Step S73the switching control unit121controls the switch133to change over the switch133to select the CEC signal from the HDMI® source71when data is transmitted and the CEC signal from the receiver82when data is received.

At Step S74the HDMI® source71receives E-EDID transmitted from the HDMI® sink72via the SDA line191of DDC83. Namely, when a connection of the HDMI® source71is detected, the HDMI® sink72reads E-EDID from EDIDROM85and transmits the read E-EDID to the HDMI® source71via the SDA line191of DDC83, thus the HDMI® source71receives E-EDID transmitted from the HDMI® sink72.

At Step S75the HDMI® source71judges whether it is possible to perform full duplex communication with the HDMI® sink72. Namely, the HDMI® source71refers to E-EDID received from the HDMI® sink72and judges whether the full duplex flag “Full Duplex” shown inFIG. 9is set, and if the full duplex flag is set, for example, the HDMI® source71judges that it is possible to perform bidirectional IP communication by a full duplex communication method, i.e., full duplex communication.

If it is judged at Step S75that full duplex communication is possible, at Step S76the switching control unit171controls the switches181and182to change over the switches181and182to select the differential signals corresponding to Rx data from the receiver82when data is received.

Namely, regarding the partial signals constituting the differential signals corresponding to Rx data transmitted from the receiver82when data is received, the switching control unit171changes over the switches181and182to make the switch181select the partial signal transmitted via the SDA line191and make the switch182select the partial signal transmitted via the SCL line192.

Since the SDA line191and the SCL line192constituting DDC83are not used after E-EDID is transmitted from the HDMI® sink72to the HDMI® source71, i.e., transmission/reception of the SDA and SCL signals via the SDA line191and SCL line192is not performed, it is possible to use the SDA line191and SCL line192as transmission lines of Rx data during full duplex communication.

At Step S77the HDMI® source71transmits a signal to the effect that IP communication by a full duplex communication method is performed using the CEC line84and signal line141and the SDA line191and SCL line192as channel information representative of a channel to be used for bidirectional communication, to the receiver82via the switch133and CEC line84.

Namely, if the full duplex flag is set, the HDMI® source71can know that the HDMI® sink72has the structure shown inFIG. 7and that it is possible to perform full duplex communication using the CEC line84and signal line141and the SDA line191and SCL line192, thus the HDMI® source71transmits the channel information to the HDMI® sink72to notify to the effect that full duplex communication is performed.

At Step S78the switching control unit121controls the switch133to change over the switch133to select the differential signals corresponding to Tx data from the converting unit131when data is transmitted. Namely, the switching control unit121changes over the switch133to select the partial signal of the differential signals corresponding to Tx data and supplied to the switch133from the converting unit131.

At Step S79each component of the HDMI® source71performs bidirectional IP communication with the HDMI® sink72by the full duplex communication method to thereafter terminate the communication process. Namely, when data is transmitted, the converting unit131converts Tx data supplied from the HDMI® source71into differential signals, and supplies one partial signal constituting the differential signals obtained by conversion to the switch133and the other partial signal to the receiver82via the signal line141. The switch133transmits the partial signal supplied from the converting unit131to the receiver82via the CEC line84. In this manner, the differential signals corresponding to Tx data are transmitted from the HDMI® source71to the HDMI® sink72.

Further, when data is received, the decoding unit183receives differential signals corresponding to Rx data transmitted from the receiver82. Namely, the switch181receives the partial signal of the differential signals corresponding to Rx data transmitted from the receiver82via the SDA line191, and supplies the received partial signal to the decoding unit183. Further, the switch182receives the other partial signal of the differential signals corresponding to Rx data transmitted from the receiver82via the SCL line192, and supplies the received partial signal to the decoding unit183. The decoding unit183decodes the differential signals constituted of the partial signals supplied from the switches181and182to the original Rx data and output the original Rx data to the HDMI® source71.

In this manner, the HDMI® source71transfers various data such as control data, pixel data and audio data with the HDMI® sink72.

Further, if it is judged at Step S75that full duplex communication is not possible, at Step S80each component of the HDMI® source71performs bidirectional communication with the HDMI® sink72through transmission/reception of the CEC signal to thereafter terminate the communication process.

Namely, when data is transmitted, the HDMI® source71transmits the CEC signal to the receiver82via the switch133and CEC line84, and when data is received, the HDMI® source71receives the CEC signal transmitted from the receiver82via the switch133and CEC line84to transfer control data with the HDMI® sink72.

In this manner, the HDMI® source71refers to the full duplex flag and performs full duplex communication with the HDMI® sink72capable of full duplex communication by using the CEC line84and signal line141and the SDA line191and SCL line192.

As described above, high speed bidirectional communication can be performed while retaining compatibility with conventional HDMI®, by selecting transmission data and reception data by changing over the switches133,181and182and performing full duplex communication with the HDMI® sink72by using the CEC line84and signal line141and the SDA line191and SCL line192.

Similar to the HDMI® sink72shown inFIG. 6, if the HDMI® sink72has the structure shown inFIG. 7, the HDMI® sink72executes a communication process to perform bidirectional communication with the HDMI® source71.

Hereinafter, with reference to the flowchart ofFIG. 13, description will be made on a communication process to be executed by the HDMI® sink72shown inFIG. 7.

At Step S111the HDMI® sink72judges whether a new electronic apparatus is connected to the HDMI® sink72. If it is judged at Step S111that the new electronic apparatus is not connected, communication is not performed to thereafter terminate the communication process.

On the other hand, if it is judged at Step S111that the new electronic apparatus is connected, then at Step S112the switching control unit172controls the switches185and186to change over the switches185and186to make the switch185select the SDA signal from the HDMI® sink72when data is transmitted, and to make the switch185select the SDA signal from the transmitter81and make the switch186select the SCL signal from the transmitter81when data is received.

At Step S113the switching control unit124controls the switch135to change over the switch135to select the CEC signal from the HDMI® sink72when data is transmitted and select the CEC signal from the transmitter81when data is received.

At Step S114the HDMI® sink72reads E-EDID from EDIDROM85, and transmits the read E-EDID to the HDMI® source71via the switch185and the SDA line191of DDC83.

At Step S115the HDMI® sink72judges whether channel information transmitted from the HDMI® source71is received.

Namely, channel information representative of a bidirectional communication channel is transmitted from the HDMI® source71in accordance with the functions possessed by the HDMI® source71and HDMI® sink72. For example, if the HDMI® source71has the structure shown inFIG. 7, the HDMI® source71and HDMI® sink72can perform full duplex communication. The HDMI® source71transmits channel information to the effect that IP communication by a full duplex communication method is performed using the CEC line84and signal line141and the SDA line191and SCL line192, to the HDMI® sink72The HDMI® sink72judges that the channel information is received, after the channel information transmitted from the HDMI® source71via the switch135and CEC line84.

On the other hand, if the HDMI® source71does not have the full duplex communication function, the channel information is not transmitted from the HDMI® source71to the HDMI® sink72so that the HDMI® sink72judges that the channel information is not received.

If it is judged at Step S115that the channel information is received, the process advances to Step S116whereat the switching control unit172controls the switches185and186to change over the switches185and186to select the differential signals corresponding to Rx data from the converting unit184when data is transmitted.

At Step S117the switching control unit124controls the switch135to change over switch135to select the differential signals corresponding to Tx data from the transmitter81when data is received.

At Step S118each component of the HDMI® sink72performs bidirectional IP communication with the HDMI® source71by the full duplex communication method to thereafter terminate the communication process. Namely, when data is transmitted, the converting unit184converts Rx data supplied from the HDMI® sink72into differential signals, and supplies one partial signal constituting the differential signals obtained by conversion to the switch185and the other partial signal to the switch186. The switches185and186transmit the partial signals supplied from the converting unit184to the transmitter81via the SDA line191and SCL line192. In this manner, the differential signals corresponding to Rx data are transmitted from the HDMI® sink72to the HDMI® source71.

Further, when data is received, the decoding unit136receives differential signals corresponding to Tx data transmitted from the transmitter81. Namely, the switch135receives the partial signal of the differential signals corresponding to Tx data transmitted from the transmitter81via the CEC line84, and supplies the received partial signal to the decoding unit136. The decoding unit136decodes the differential signals constituted of the partial signal supplied from the switch135and the partial signal supplied from the transmitter81via the signal line141to the original Tx data and output the original Tx data to the HDMI® sink72.

In this manner, the HDMI® sink72transfers various data such as control data, pixel data and audio data with the HDMI® source71.

If it is judged at Step S115that the channel information is not received, at Step S119each component of the HDMI® sink72performs bidirectional communication with the HDMI® source71through transmission/reception of the CEC signal to thereafter terminate the communication process.

In this manner, when the channel information is received, the HDMI® sink72performs full duplex communication with the HDMI® sink72via the CEC line84and signal line141and the SDA line191and SCL line192.

As described above, high speed bidirectional communication can be performed while retaining compatibility with conventional HDMI®, by performing full duplex communication between the HDMI® sink72and HDMI® source71using the CEC line84and signal line141and the SDA line191and SCL line192and by changing over the switches135,185and186to select transmission data and reception data.

Note that, although in the example inFIG. 7, the HDMI® source71is structured such that the converting unit131is connected to the CEC line84and signal line141, and the decoding unit183is connected to the SDA line191and SCL line192, the structure may be that the decoding unit183is connected to the CEC line84and signal line141and the converting unit131is connected to the SDA line191and SCL line192.

In such case, the switches181and182are connected to the CEC line84and signal line141respectively and to the decoding unit183, and the switch133is connected to the SDA line191and to the converting unit131.

Similarly, the HDMI® sink72shown inFIG. 7may be structured such that the converting unit184is connected to the CEC line84and signal line141and the decoding unit136is connected to the SDA line191and SCL line192. In such case, the switches185and186are connected to the CEC line84and signal line141respectively and to the converting unit184, and the switch135is connected to the SDA line191and to the decoding unit136.

Further, inFIG. 6, the CEC line84and signal line141may be replaced with the SDA line191and SCL line192. Namely, the converting unit131and decoding unit132of the HDMI® source71, and the converting unit134and decoding unit136of the HDMI® sink72are connected to the SDA line191and SCL line192to make the HDMI® source71and HDMI® sink72perform IP communication by a half duplex communication method. In this case, a connection of an electronic apparatus may be detected by utilizing a reserved pin of the connector connected to the signal line141.

Further, each of the HDMI® source71and HDMI® sink72may have both the half duplex communication function and the full duplex communication function. In this case, the HDMI® source71and HDMI® sink72can perform IP communication by a half duplex communication method or full duplex communication method in accordance with the functions possessed by the connected electronic apparatus.

If each of the HDMI® source71and HDMI® sink72has both the half duplex communication function and the full duplex communication function, the HDMI® source71and HDMI® sink72are structured, for example, as shown inFIG. 14. Note that, inFIG. 14, parts corresponding to those shown inFIG. 6or7are represented by identical symbols, and the description thereof is omitted where proper.

An HDMI® source71shown inFIG. 14is constituted of a transmitter81, a switching control unit121, a timing control unit122and a switching control unit171, and the transmitter81has a converting unit131, a decoding unit132, a switch133, a switch181, a switch182and a decoding unit183. Namely, the HDMI® source71shown inFIG. 14has a structure that the timing control unit122and decoding unit132shown inFIG. 6are added to the HDMI® source71shown inFIG. 7.

An HDMI® sink72shown inFIG. 14is constituted of a receiver82, a timing control unit123, a switching control unit124, and a switching control unit172, and the receiver82has a converting unit134, a switch135, a decoding unit136, a converting unit184, a switch185and a switch186. Namely, the HDMI® sink72shown inFIG. 14has a structure that the timing control unit123and converting unit134shown inFIG. 6are added to the HDMI® sink72shown inFIG. 7.

Next, description will be made on a communication process to be executed by the HDMI® source71and HDMI® sink72shown inFIG. 14.

First, with reference to the flowchart shown inFIG. 15, description will be made on a communication process to be executed by the HDMI® source71shown inFIG. 14. Note that processes at Steps S151to S154are similar to the processes at Steps S71to S74shown inFIG. 12, and so the description thereof is omitted.

At Step S155the HDMI® source71judges whether it is possible to perform full duplex communication with the HDMI® sink72. Namely, the HDMI® source71refers to E-EDID received from the HDMI® sink72and judges whether the full duplex flag “Full Duplex” shown inFIG. 9is set.

If it is judged at Step S155that full duplex communication is possible, i.e., if the HDMI® sink72shown inFIG. 14orFIG. 7is connected to the HDMI® source71, at Step S156the switching control unit171controls the switches181and182to change over the switches181and182to select the differential signals corresponding to Rx data from the receiver82when data is received.

If it is judged at Step S155that full duplex communication is not possible, at Step S157the HDMI® source71judges whether half duplex communication is possible. Namely, the HDMI® source71refers to the received E-EDID and judges whether the half duplex flag “Half Duplex” shown inFIG. 9is set. In other words, the HDMI® source71judges whether the HDMI® sink72shown inFIG. 6is connected to the HDMI® source71.

If it is judged at Step S157that half duplex communication is possible, or if the switches181and182are changed over at Step S156, then at Step S158the HDMI® source71transmits channel information to the receiver82via the switch133and CEC line84.

If it is judged at Step S155that full duplex communication is possible, since the HDMI® sink72has the full duplex communication function, the HDMI® source71transmits a signal to the effect that IP communication is performed using the CEC line84and signal line141and the SDA line191and SCL line192, as channel information, to the receiver82via the switch133and CEC line84.

If it is judged at Step S157that half duplex communication is possible, since the HDMI® sink72has the half duplex communication function although it does not have the full duplex communication function, the HDMI® source71transmits a signal to the effect that IP communication is performed using the CEC line84and signal line141, as channel information, to the receiver82via the switch133and CEC line84.

At Step S159the switching control unit121controls the switch133to change over the switch133to select the differential signals corresponding to Tx data from the converting unit131when data is transmitted, and to select the differential signals corresponding to Rx data transmitted from the receiver82when data is received. Note that if the HDMI® source71and HDMI® sink72perform full duplex communication, the differential signals corresponding to Rx data are not transmitted from the receiver82via the CEC line84and signal line141when the HDMI® source71receives data, so that the differential signals corresponding to Rx data are not supplied to the decoding unit132.

At Step S160each component of the HDMI® source71performs bidirectional IP communication with the HDMI® sink72to thereafter terminate the communication process.

Namely, when the HDMI® source71performs full duplex communication and half duplex communication with the HDMI® sink72, the converting unit131converts Tx data supplied from the HDMI® source71into differential signals when data is transmitted, and supplies one partial signal constituting the differential signals obtained by conversion to the receiver82via the switch133and CEC line84and the other partial signal to the receiver82via the signal line141.

Further, when the HDMI® source71performs full duplex communication with the HDMI® sink72and when data is received, the decoding unit183receives the differential signals corresponding to Rx data transmitted from the receiver82, and decodes the received differential signals to the original Rx data and output the original Rx data to the HDMI® source71.

Whereas, when the HDMI® source71performs half duplex communication with the HDMI® sink72and when data is received, under the control of the timing control unit122, the decoding unit132receives the differential signals corresponding to Rx data transmitted from the receiver82, and decodes the received differential signals to the original Rx data and output the original Rx data to the HDMI® source71.

In this manner, the HDMI® source71transfers various data such as control data, pixel data and audio data with the HDMI® sink72.

Further, if it is judged at Step S157that half duplex communication is not possible, at Step S161each component of the HDMI® source71performs bidirectional communication with the HDMI® sink72through transmission/reception of the CEC signal via the CEC line84to thereafter terminate the communication process.

In this manner, the HDMI® source71refers to the full duplex flag and half duplex flag and performs full or half duplex communication with the HDMI® sink72in accordance with the function possessed by the communication partner HDMI® sink72.

As described above, high speed bidirectional communication can be performed while retaining compatibility with conventional HDMI® and selecting an optimum communication method, by selecting transmission data and reception data by changing over the switches133,181and182and performing full or half duplex communication with the HDMI® sink72in accordance with the functions possessed by the communication partner HDMI® sink72.

Next, with reference to the flowchart shown inFIG. 16, description will be made on a communication process to be executed by the HDMI® sink72shown inFIG. 14. Note that processes at Steps S191to S194are similar to the processes at Steps S111to S114shown inFIG. 13, and so the description thereof is omitted.

At Step S195the HDMI® sink72receives channel information transmitted from the HDMI® source71via the switch135and CEC line84. Note that if the HDMI® source71connected to the HDMI® sink72has neither the full duplex communication function nor the half duplex communication function, the channel information will not transmitted from the HDMI® source71to the HDMI® sink72, the HDMI® sink72will not receive the channel information.

At Step S196the HDMI® sink72judges from the received channel information whether full duplex communication is performed. For example, the HDMI® sink72judges that full duplex communication is performed, if the HDMI® sink72receives the channel information to the effect that IP communication is performed using the CEC line84and signal line141and the SDA line191and SCL line192.

If it is judged at Step S196that full duplex communication is performed, then at Step S197the switching control unit172controls the switches185and186to change over the switches185and186to select the differential signals corresponding to Rx data from the converting unit184when data is transmitted.

Further, if it is judged at Step S196that full duplex communication is not performed, then at Step S198the HDMI® sink72judges from the received channel information whether half duplex communication is performed. For example, the HDMI® sink72judges that half duplex communication is performed, if the HDMI® sink72receives the channel information to the effect that IP communication using the CEC line84and signal line141is received.

If it is judged at Step S198that half duplex communication is performed or if the switches185and186are changed over at Step S197, then at Step199the switching control unit124controls the switch135to change over switch135to select the differential signals corresponding to Rx data from the converting unit134when data is transmitted and to select the differential signals corresponding to Tx data from the transmitter81when data is received.

Note that if the HDMI® source71and HDMI® sink72perform full duplex communication, the differential signals corresponding to Rx data are not transmitted from the converting unit134to the transmitter81when data is transmitted at the HDMI® sink72. Therefore, the differential signals corresponding to Rx data are not supplied to the switch135.

At Step S200, each component of the HDMI® sink72performs bidirectional IP communication with the HDMI® source71to thereafter terminate the communication process.

Namely, if the HDMI® sink72and HDMI® source71perform full duplex communication and when data is transmitted, the converting unit184converts Rx data supplied from the HDMI® sink72into differential signals, and supplies one partial signal constituting the differential signals obtained by conversion to the transmitter81via the switch185and SDA line191and the other partial signal to the transmitter81via the switch186and SCL line192.

Further, if the HDMI® sink72and HDMI® source71perform half duplex communication and when data is transmitted, the converting unit134converts Rx data supplied from the HDMI® sink72into differential signals, and supplies one partial signal constituting the differential signals obtained by conversion to the transmitter81via the switch135and CEC line84and the other partial signal to the transmitter81via the signal line141.

Further, if the HDMI® sink72and HDMI® source71perform full duplex communication and half duplex communication and when data is received, the decoding unit136receives the differential signals corresponding to Tx data transmitted from the transmitter81, and decodes the received differential signals to the original Tx data and output the original Tx data to the HDMI® sink72.

In addition, if it is judged at Step S198that half duplex communication is not performed, i.e., for example, the channel information is not transmitted, when at Step S201each component of the HDMI® sink72performs bidirectional communication with the HDMI® source71through transmission/reception of the CEC signal to thereafter terminate the communication process.

In this manner, the HDMI® sink72performs full duplex communication or half duplex communication in accordance with the received channel information, i.e., in accordance with the function possessed by the communication partner HDMI® source71.

As described above, high speed bidirectional communication can be performed while retaining compatibility with conventional HDMI® and selecting an optimum communication method, by performing full duplex communication or half duplex communication between the HDMI® sink72and HDMI® source71and by changing over the switches135,185and186to select transmission data and reception data in accordance with the function possessed by the communication partner HDMI® source71.

Further, high speed bidirectional IP communication by a half duplex communication method or full duplex communication method can be performed while retaining compatibility with a conventional HDMI® cable, by connecting the HDMI® source71and HDMI® sink72by the HDMI® cable35which contains the CEC line84and signal line141wired as a differential twist pair and shielded and connected to the ground line and the SDA line191and SCL line192wired as a differential twist pair and shielded and connected to the ground line.

As described above, any one of one or a plurality of data sets is selected as transmission data, the selected data is transmitted to a communication partner via a predetermined signal line, any one of one or a plurality of data sets transmitted from the communication partner is selected as reception data, and the selected data is received. Accordingly, high speed bidirectional IP communication can be performed via the HDMI® cable35between the HDMI® source71and HDMI® sink72while retaining compatibility with HDMI®, i.e., while allowing uncompressed image pixel data to be transmitted unidirectionally at high speed from the HDMI® source71to the HDMI® sink72.

As a result, if a source apparatus, e.g., an electronic apparatus such as the reproducing apparatus33shown inFIG. 2, mounting therein the HDMI® source71, has a server function such as DLNA (Digital living Network Alliance), and a sink apparatus, e.g., an electronic apparatus such as the digital television set31shown inFIG. 2, mounting therein the HDMI® sink72, has a LAN communication interface such as Ethernet (Registered Trademark), it is possible to transmit content from the source apparatus to the sink apparatus via the HDMI® cable and to transmit the content from the source apparatus, from the sink apparatus to another apparatus (e.g., the digital television set34shown inFIG. 2) connected to the LAN communication interface of the sink apparatus, by direct bidirectional IP communication or bidirectional IP communication via an electronic apparatus such as the amplifier32connected by the HDMI® cable.

Further, with the bidirectional IP communication between the HDMI® source71and HDMI® sink72, control commands and responses can be transferred at high speed between a source apparatus mounting therein the HDMI® source71and a sink apparatus mounting therein the HDMI® sink72interconnected by the HDMI® cable35, thus it is possible to control apparatus by high speed responses.

Next, the above-described series of processes may be realized by dedicated hardware or software. If a series of processes are to be realized by software, the program constituting the software is installed in microcomputers or the like which controls the HDMI® source71and HDMI® sink72.

FIG. 17shows an example of a structure of a computer installed with the program for executing the above-described series of processes, according to an embodiment.

The program may be recorded in an EEPROM (Electrically Erasable Programmable Read-only Memory)305or a ROM303as a recording medium mounted in the computer.

Alternatively, the program may be temporarily or perpetually stored (recorded) in a removable recording medium such as a flexible disc, a CD-ROM (Compact Disc Read-Only Memory), a MO (Magneto Optical) disc, a DVD (Digital Versatile Disc), a magnetic disc and a semiconductor memory. This removable recording medium may be presented as so-called package software.

Note that the program may be installed from the removable recording medium as described above into the computer, may be wireless-transferred from a download site to the computer via a digital satellite broadcasting artificial satellite, or may be wired-transferred to the computer via a network such as a LAN and the Internet, and the computer receives the transferred program at an I/O interface306and installs the program in a built-in EEPROM305.

The computer has a built-in CPU (Central Processing Unit)302. The CPU302is connected to the I/O interface306via a bus301, and loads the program stored in a ROM (Read-Only Memory)303or an EEPROM305in a RAM (Random Access Memory)304to execute the program. Accordingly, the CPU302executes the processes in the above-described flowcharts and the processes to be performed by the structures shown in the above-described block diagrams.

Herein, in this specification, process steps describing the program for making a computer execute various processes are not necessarily required to be executed time sequentially in the order of written statements in the flowcharts, but may contain a process to be executed parallel or independently (e.g., a parallel process or a process by an object).

Further, the program may be executed by one computer or distributively executed by a plurality of computers.

It should be noted that the present invention is applicable to a communication interface constituted of a transmission apparatus for unidirectionally transmitting differential signals corresponding to pixel data of an uncompressed image of one screen, to a reception apparatus via a plurality of channels in an effective video period which is a period from one vertical synchronization signal to the next vertical synchronization signal subtracting horizontal blanking periods and a vertical blanking period, and the reception apparatus for receiving the differential signals transmitted from the transmission apparatus via the plurality of channels.

In the embodiment, bidirectional IP communication is performed by controlling when necessary a data selection timing, a differential signal reception timing and a differential signal transmission timing between the HDMI® source71and HDMI® sink72, but bidirectional communication may be performed in accordance with a protocol different from IP.

It should be noted that the embodiment of the present invention is not limited to the above-described embodiment, but various modifications are possible without departing from the features of the present invention.

According to the embodiment described above, bidirectional communication is possible. Specifically, bidirectional communication at high speed can be performed while retaining compatibility, in a communication interface capable of transmitting pixel data of an uncompressed image and audio data accompanied by the pixel data unidirectionally at high speed.

Incidentally, although partially overlapping the already described techniques, many audio/video apparatuses are provided with a LAN communication function for the purposes of viewing bidirectional programs, sophisticated remote control, receiving an electronic program table and the like.

As a means for forming a network among audio/video apparatuses, there are selection candidates such as wiring a dedicated cable such as CAT5, wireless communication, and electric light wire communication.

However, a dedicated cable makes complicate the connection among apparatus, and wireless communication and electric light wire communication have disadvantages that a complicated modulation circuit and a transceiver are expensive.

Therefore, the above-described embodiment discloses the techniques of adding a LAN communication function without adding a new connector electrode to HDMI.

Since HDMI is an interface for performing video data and audio data transmission, replacement and authentication of connected apparatus information, and communication of apparatus control data by using one cable, HDMI has a large advantage that LAN communication can be performed with an added LAN function, without using a dedicated cable and wireless communication or the like.

Incidentally, the techniques disclosed as the above-described embodiment provides that the differential transmission lines used by LAN communication serve as replacement and authentication of connected apparatus information and communication of apparatus control data.

With HDMI, a parasitic capacitance and an impedance of the connected apparatus electric characteristics have severe restrictions not only on DDC performing replacement and authentication of connected apparatus information but also on CEC for communication of apparatus control data.

Specifically, a DDC terminal parasitic capacitance of an apparatus is required to be 50 pF or smaller, and an impedance is required to be grounded to ground GND at 200Ω or smaller when LOW is output and to be pulled up to a power source at about 2Ω in HIGH state.

Meanwhile, transmission/reception terminals are required to be terminated at least at about 100Ω in a high frequency band in order to stabilize LAN communication which transmits a high speed signal.

FIG. 19shows the state that a transmitter404and a transmitter405for LAN communication are AC-coupled always to DDC lines of an existing HDMI source apparatus401and an existing HDMI sink apparatus402.

In order to satisfy the DDC parasitic capacitance restrictions, it is required that a LAN transmitter/receiver circuit added to the DDC lines has AC coupling via a sufficiently small capacitance. Therefore, a LAN signal is attenuated greatly and has distortion so that the transmitter and receiver capable of compensating this may become complicated and expensive.

Further, transition between HIGH and LOW states during DDC communication may hinder LAN communication. Namely, there is a fear that LAN does not function during DDC communication.

Therefore, in the following, description will be made on a communication system as a more preferred embodiment, which is characterized in that in the interface which performs video data and audio data transmission, replacement and authentication of connected apparatus information, communication of apparatus control data and LAN communication by using basically one cable, the LAN communication is performed by bidirectional communication via a pair of differential transmission lines, and a connection state of the interface is notified by at least one DC bias potential of the transmission lines.

The techniques described hereunder are not necessarily required to have the selection units as in the above-described embodiment.

FIG. 18is a circuit diagram showing an example of a first structure of the communication system in which a connection state of the interface is notified by at least one DC bias potential of the transmission lines.

FIG. 19shows an example of the system when used in Ethernet (Registered Trademark).

As shown inFIG. 18, this communication system400is constituted of a LAN function expansion HDMI (hereinafter abbreviated to EH) source apparatus401, an EH sink apparatus402, an EH cable403for interconnecting the EH source apparatus and EH sink apparatus, an Ethernet (Registered Trademark) transmitter404and an Ethernet (Registered Trademark) receiver405.

The EH source apparatus401has a LAN signal transmitter circuit411, a terminating resistor412, AC coupling capacitors413and414, a LAN signal receiver circuit415, a subtracting circuit416, a pull-up resistor421, a resistor422and a capacitor423forming a low-pulse filter, a comparator424, a pull-down resistor431, a resistor432and a capacitor433forming a low-pass filter, and a comparator434.

The EH cable403has differential transmission lines constituted of a reserved line501and an HPD Line502which are provided with a source side terminal511of the reserved line501, a source side terminal512of the HPD Line502, a sink side terminal521of the reserved line501and a sink side terminal522of the HPD line. The reserved line501and HPD line502are wired as a differential twist pair.

In the communication system400constructed as above, the terminals511and512are connected in the source apparatus401, via the AC coupling capacitors413and414to the terminating resistor412, LAN signal transmitter circuit411and LAN signal receiver circuit415.

The subtracting circuit416receives a sum signal SG412of a transmission signal voltage generated by current output from the LAN signal transmitter circuit411by a load of the terminating resistor412and transmission lines501and502and a reception signal voltage of a signal transmitted from the EH sink apparatus402.

In the subtracting circuit416, a signal SG413obtained by subtracting the transmission signal SG411from the sum signal SG412is a net signal transmitted from the sink.

The sink apparatus402has a similar circuit network. With these circuit networks, the source apparatus401and sink apparatus402perform bidirectional LAN communication.

In addition to the above-described LAN communication, the HPD line502notifies the source apparatus401of that the cable403is connected to the sink apparatus402, by using a DC bias level.

The resistors462and463and choke coil461of the sink apparatus402bias the HPD line502to about 4V via the terminal522when the cable403is connected to the sink apparatus402.

The source apparatus401extracts a DC bias at the HPD line502by the low-pass filter made of the resistor432and capacitor433, and the comparator434compares the DC bias with the reference potential Vref2(e.g, 1.4 V).

If the cable403is not connected to the source apparatus402, a potential at the terminal512is lower than the reference potential Vref2because of the pull-down resistor431, whereas if connected, the potential is higher then the reference potential.

Therefore, if an output signal SG415of the comparator434is HIGH, it means that the cable403is connected to the sink apparatus402.

If the output signal SG415of the comparator434is LOW, it means that the cable403is not connected to the sink apparatus402.

The example of the first structure further has a function of mutually recognizing from a DC bias potential at the reserved line501whether the apparatus connected at opposite ends of the cable403are EH compatible apparatus or HDMI apparatus not compatible with EH.

The EH source apparatus401pulls up (+5 V) the reserved line501by the resistor421, and the EH sink apparatus402pulls down the reserved line by the resistor451.

These resistors421and451do not exist in the apparatus not compatible with EH.

The EH source apparatus401compares by the comparator424a DC potential at the reserved line501passed through the low-pass filter made of the resistor422and capacitor423with the reference voltage Vref1.

If the sink apparatus402is compatible with EH and has a pull-down function, the potential at the reserved line501is 2.5 V, and if the sink apparatus is not compatible with EH and has no pull-down function, the potential at the reserved line is 5 V. Therefore, if the reference potential Vref1is 3.75 V, it is possible to distinguish between a compatible sink apparatus and an incompatible sink apparatus.

The sink apparatus402compares by the comparator454a DC potential at the reserved line501passed through the low-pass filter made of the resistor452and capacitor453with the reference voltage Vref3.

If the source apparatus402is compatible with EH and has a pull-up function, the potential is 2.5 V, and if the source apparatus is not compatible with EH, the potential is 0 V. Therefore, if the reference potential is 1.25 V, it is possible to distinguish between an EH compatible source apparatus and an EH incompatible source apparatus.

As described above, according to the example of the first structure, in the interface which performs video data and audio data transmission, replacement and authentication of connected apparatus information, communication of apparatus control data and LAN communication by using one cable403, the LAN communication is performed by bidirectional communication via a pair of differential transmission lines, and a connection state of the interface is notified by at least one DC bias potential of the transmission lines. It is therefore possible to physical and spatial separation of the SCL line and SDA line such that they are not used for LAN communication.

As a result, this division allows a LAN communication circuit to be formed independently from the electric specifications stipulated for DDC, and stable and reliable LAN communication can be realized at low cost.

It should be noted that the pull-up resistor421shown inFIG. 18may be provided not in the EH source apparatus401, but in the EH cable403. In such case, each terminal of the pull-up resistor421is connected to the reserved line501and a line (signal line) connected to a power source (power source potential), respectively, out of the lines provided within the EH cable403.

Further, the pull-down resistor451and the resistor463may be provided not in the EH sink apparatus402, but in the EH cable403. In such case, each terminal of the pull-down resistor451is connected to the reserved line501and a line (ground line) connected to a ground (reference potential), respectively, out of the lines provided within the EH cable403. In addition, each terminal of the resistor463is connected to the HPD line502and the line (ground line) connected the ground (reference potential), respectively, out of the lines provided within the EH cable403.

FIG. 20is a circuit diagram showing an example of a second structure of the communication system in which a connection state of the interface is notified by at least one DC bias potential of the transmission lines.

Fundamentally similar to the example of the first structure, this communication system600is characterized in a structure that in the interface which performs video data and audio data transmission, replacement and authentication of connected apparatus information, communication of apparatus control data and LAN communication by using one cable, the LAN communication is performed by unidirectional communication via two pairs of differential transmission lines, and a connection state of the interface is notified by at least one DC bias potential of the transmission lines, and that at least two transmission lines are used for communication of replacement and authentication of connected apparatus information, time divisionally with LAN communication.

As shown inFIG. 20, this communication system600is constituted of a LAN function expansion HDMI (hereinafter abbreviated to EH) source apparatus601, an EH sink apparatus602and an EH cable603for interconnecting the EH source apparatus and EH sink apparatus.

The EH source apparatus601has a LAN signal transmitter circuit611, terminating resistor612and613, AC coupling capacitors614to617, a LAN signal receiver circuit618, an inverter620, a resistor621, a resistor622and a capacitor623forming a low-pulse filter, a comparator624, a pull-down resistor631, a resistor632and a capacitor633forming a low-pass filter, a comparator634, a NOR gate640, analog switches641to644, an inverter635, analog switches646and747, DDC transceivers651and652and pull-up resistors653and654.

The EH sink apparatus602has a LAN signal transmitter circuit661, terminating resistors662and663, AC coupling capacitors664to667, a LAN signal receiver circuit668, a pull-down resistor671, a resistor672and a capacitor673forming a low-pulse filter, a comparator674, a choke coil681, resistors682and683serially connected between a power source potential and a reference potential, analog switches691to694, inverter695, analog switches696and697, DDC transceivers701and702, and a pull-up resistor703.

The EH cable603has differential transmission lines constituted of a reserved line801and an SCL line803and differential transmission lines constituted of an SDA line804and an HPD line802, which are provided with source side terminal811to814and sink side terminals821to824.

The reserved line801and SCL line803and the SDA line804and HPD line802are wired as differential twist pairs.

In the communication system600constructed as above, the terminals811and813are connected in the source apparatus601via the AC coupling capacitors614and615and the analog switches641and642, to the transmitter circuit611for transmitting a LAN transmission signal SG611to the sink, and to the terminating resistor612.

The terminals814and812are connected via the AC coupling capacitors616and617and the analog switches643and644, to the receiver circuit618for receiving a LAN signal from the sink apparatus602, and to the terminating resistor613.

In the sink apparatus602, the terminals821to824are connected via the AC coupling capacitors664,665,666and667and analog switches691to694to the transmitter and receiver circuits668and661and terminating resistors662and663.

The analog switches641to644and691to694turn on when LAN communication is performed and turn off when DDC communication is performed.

The source apparatus601connects the terminals813and814to the DDC transceivers651and652and pull-up resistors653and654via other analog switches646and647.

The sink apparatus602connects the terminals823and824to the DDC transceivers701and702and pull-up resistor703via the analog switches696and697.

The analog switches646,647,696and697turn on when DDC communication is performed and turn off when DLAN communication is performed.

The recognition mechanism of an EH compatible apparatus by a potential at the reserved line801is basically the same as that of the example of the first structure, except that the resistor62of the source apparatus601is driven by the inverter620.

When an input to the inverter620is HIGH, the resistor621is used as a pull-down resistor providing a 0 V state which is the same state as an EH compatible apparatus is connected as viewed from the sink apparatus602.

As a result, a signal SG623indicating an EH compatibility identification result of the sink apparatus602becomes LOW so that the analog switches691to694controlled by the signal SG623turn off and the analog switches696and697controlled by a signal obtained by inverting the signal SG623at the inverter695turn on.

As a result, the sink apparatus602enters the DDC transceiver connected state by disconnecting the SCL line803and SDA line804from the LAN transceiver.

Meanwhile, in the source apparatus601, an input to the inverter620is also input to the NOR gate640whose output SG614becomes LOW.

The analog switches641to6444controlled by the output signal SF614of the NOR gate640turn off, and the analog switches646and647controlled by a signal obtained by inverting the signal SF614at the inverter645turn on.

As a result, the source apparatus601also enters the DDC transceiver connected state by disconnecting the SCL line803and SDA line804from the LAN transceiver.

Conversely, when an input to the inverter620is LOW, both the source apparatus601and sink apparatus602enter the LAN transceiver connected state by disconnecting the SCL line803and SDA line804from the DDC transceiver.

The circuits631to634and681to683for the connection confirmation by a DC bias potential at the HPD line802have the function similar to that of the example of the first structure.

Namely, the HPD Line802is used for the above-described LAN communication, and in addition notifies the source apparatus601of that the cable803is connected to the sink apparatus602, by using the DC bias level.

The resistors682and683and choke coil681within the sink apparatus602bias the HPD line802via the terminal822to about 4 V, when the cable603is connected to the sink apparatus602.

The source apparatus601extracts a DC bias at the HPD line802by the low-pass filter made of the resistor632and capacitor633, and compares by the comparator634the DC bias with the reference potential Vref2(e.g, 1.4 V).

If the cable603is connected to the source apparatus602, a potential at the terminal812is lower than the reference potential Vref2because of the pull-down resistor631, whereas if connected, the potential is higher then the reference potential.

Therefore, if an output signal SG613of the comparator634is HIGH, it means that the cable803is connected to the sink apparatus602.

On the other hand, if the output signal SG613of the comparator634is LOW, it means that the cable603is not connected to the sink apparatus602.

As described above, according to the example of the second structure, in the interface which performs video data and audio data transmission, replacement and authentication of connected apparatus information, communication of apparatus control data and LAN communication by using one cable, the LAN communication is performed by unidirectional communication via two pairs of differential transmission lines, and a connection state of the interface is notified by at least one DC bias potential of the transmission lines, and further at least two transmission lines are used for communication of replacement and authentication of connected apparatus information, time divisionally with LAN communication. This division allows a LAN communication circuit to be formed independently from the electric specifications stipulated for DDC, and stable and reliable LAN communication can be realized at low cost.

It should be noted that the resistor621shown inFIG. 20may be provided not in the EH source apparatus601, but in the EH cable603. In such case, terminals of the resistor621are connected to the reserved line801and a line (signal line) connected to a power source (power source potential), respectively, out of the lines provided within the EH cable603.

Further, the pull-down resistor671and the resistor683may be provided not in the EH sink apparatus602, but in the EH cable603. In such case, terminals of the pull-down resistor671are connected to the reserved line801and a line (ground line) connected to a ground (reference potential), respectively, out of the lines provided within the EH cable603. In addition, terminals of the resistor683are connected to the HPD line802and the line (ground line) connected the ground (reference potential), respectively, out of the lines provided within the EH cable603.

As described so far, in the embodiment related toFIGS. 2 to 17, of nineteen HDMI pins, SDA and SCL are used as a first differential pair, and CEC and Reserved are used as a second pair to perform unidirectional communication at each pair and realize full duplex communication.

However, with SDA and SCL, communication is performed at 1.5 KO pull-up for HIGH and at a low impedance for LOW, whereas also with CEC, communication is performed at 27 KΩ pull-up for HIGH and at a low impedance for LOW.

Retaining these functions in order to have compatibility with existing HDMI may lead to a fear that it becomes difficult to share the functions of high-speed data communication LAN which is required to have impedance matching at terminating ends of a transmission line.

Therefore, in the example of the first structure, full duplex communication is realized by one-pair bidirectional communication using a differential pair of Reserved and HPD to avoid the use of SDA, SCL and CEC lines.

Since HPD is a flag signal at a DC level, injection of a LAN signal by AC coupling and transmission of plug information at a DC level are both satisfied. Reserved is provided with a new function of mutually recognizing a terminal having a LAN function by using a DC level and a method similar to HPD.

In the example of the second structure, two-pair full duplex communication is realized by unidirectional communication at each of two differential pairs of HPD and SDA, and SCL and Reserved.

Timings of burst-like DDC communication by SDA and SCL of HDMI are controlled in a state that the transmitter is always a master.

In this example, the analog switches are operated such that when a transmitter performs DDC communication, SDA and SCL lines are connected to the DDC transceiver, and when a transmitter does not perform DDC communication, the lines are connected to the LAN transceiver.

These switch control signals are also transmitted to a receiver at a DC level of the Reserved line, and switches are changed over also on the receiver side.

Adopting these structures provides a first advantage that SCL, SDA and CEC communication will not influenced by noises of LAN communication and stable DDC and CEC communication can be established always.

This is because in the example of the first structure, LAN is separated physically from lines and in the example of the second structure, LAN signal is disconnected from lines by switches during DDC communication.

A second advantage is that stable communication having a large margin can be realized because LAN communication is performed by using lines having ideal terminations.

This is because in the example of the first structure, the terminating impedance can be maintained at an ideal value in a sufficiently broad frequency band necessary for LAN communication in which a LAN signal is superposed upon Reserved and HPD lines which transmits a signal only at a DC level, and in the example of the second structure, LAN terminating circuits not permitted for DDC communication are connected by switches only during LAN communication.

FIGS. 21A to 21Eare diagrams showing the bidirectional communication waveforms on the communication system of the examples of the structures.

FIG. 21Ashows signal waveforms sent from an EH sink apparatus,FIG. 21Bshows signal waveforms receives at the EH sink apparatus,FIG. 21Cshows signal waveforms passing in the cable,FIG. 21Dshows signals received at an EH source apparatus, andFIG. 21Eshows signal waveforms sent from the EH source apparatus.

As shown inFIG. 21, good bidirectional communication can be realized by using the examples of the structures.

Next, a description will be made on an embodiment of a content decoding system using the communication system described above.

FIG. 22is a diagram showing a structure of the content decoding system according to the embodiment of the present invention.

As shown inFIG. 22, the content decoding system according to this embodiment is constituted of a television apparatus1(hereinafter, referred to as TV1), an AV amplifier2, a game apparatus3and a PC4.

The TV1is connected to the AV amplifier2by HDMI, and the AV amplifier2is further connected to the game apparatus3and PC4, also by HDMI. In this embodiment, the TV1functions as a sink apparatus in HDMI, and the game apparatus3and PC4function as source apparatuses in HDMI. Further, the TV1is connected to a server5on the Internet6via Ethernet (Registered Trademark).

The TV1is operable by a user using a remote controller911. By inputting an operation of the user from the remote controller911to the TV1, the TV1can receive broadcast content by broadcast signals, and receive content on the Internet6from the server5.

The AV amplifier2receives via HDMI an audio signal of the content received from the broadcast signals or the Internet6, or content stored in the game apparatus3or PC4, and amplifies the audio signals to output the audio signals from a multi-channel surround speaker (not shown) using 5.1 channels or the like, that is connected to the AV amplifier2. Further, the AV amplifier2outputs video signals of the content received from the game apparatus3or PC4via HDMI to the TV1via HDMI. The TV1displays the video signals by a display panel. In addition, the AV amplifier2receives via HDMI the video signals and the audio signals of the content received by the TV1and transfers the video signals and the audio signals to the game apparatus3or the PC4 via HDMI. The game apparatus3or the PC4records the video signals and the audio signals on respective recording mediums thereof, such as HDDs.

The server5stores, in addition to various video content and audio content, various Web pages to be displayed in browsers of the TV1, the game apparatus3and the PC4, software and the like capable of being downloaded by the TV1, the game apparatus3and the PC4.

FIG. 23is a block diagram showing a structure of the TV1.

As shown inFIG. 23, the TV1has a digital antenna input terminal912, a digital tuner913, an MPEG decoder914, a video signal processing circuit915, a graphic generation unit916, a panel driving circuit917, a display panel918, an audio signal processing circuit919, an audio amplifier circuit920, a speaker921, an expanded HDMI terminal922, an expanded HDMI receiving unit923, a high-speed data line I/F (interface)924, a CPU (Central Processing Unit)925, a flash memory926, DRAM (Dynamic Random Access Memory)927, an internal bus928, an Ethernet (Registered Trademark) I/F929, an Ethernet (Registered Trademark) terminal930, and a remote controller light receiving unit931.

The digital antenna input terminal912inputs broadcast signals of digital broadcast received by a digital antenna (not shown). The digital tuner913selects signals of a specified channel out of the broadcast signals, and performs frequency-conversion of the selected signals into baseband signals to output the baseband signals to the MPEG decoder914. The MPEG decoder914decodes the encoded AV baseband signals to output video signals of the decoded signals to the video signal processing circuit915, and audio signals of the decoded signals to the audio signal processing circuit919.

The video signal processing circuit915applies requisite video processes to the input video signals, and outputs the processed signals to the graphic generation unit916. The graphic generation unit916synthesizes the input video signals with a GUI (Graphical User Interface) screen and the like by an OSD (On Screen Display) process, and outputs the synthesized signals to the panel driving circuit917. The panel driving circuit917performs D/A conversion and the like of the video signals provided from the graphic generation unit916, and drives the display panel918in accordance with the analog-converted video signals. The display panel918is an LCD (Liquid Crystal display), a PDP (Plasma Display Panel) or the like, and displays the analog video signals input from the panel driving circuit917.

The audio signal processing circuit919applies requisite audio processes to the input audio signals, and outputs the processed signals to the audio amplifier circuit920. The audio amplifier circuit920adjusts the input audio signals to requisite volume and outputs the adjusted signals to the speaker921to reproduce them.

The expanded HDMI terminal922is obtained by expanding a conventional HDMI terminal such that the bidirectional communication by a high-speed data line can be performed. The expanded HDMI terminal922is connected to the AV amplifier2via an HDMI cable, and inputs video signals and audio signals of various content and various other signals from the game apparatus3and the PC4via the AV amplifier2, and outputs baseband signals to those apparatuses. The expanded HDMI receiving unit923receives the baseband signals input from the expanded HDMI terminal922and outputs the baseband signals to the video signal processing circuit915. The high-speed data line I/F924inputs the signals input via the high-speed data lines out of the signals input from the expanded HDMI terminal922, and applies various signal processes to the input signals to output the processed signals to the Ethernet (Registered Trademark) I/F929.

The CPU925accesses the DRAM927and the like when necessary, to perform overall control on each block of the TV1. The flash memory926is a non-volatile memory in which firmware such as OSs and programs to be executed by the CPU925and various parameters is stored fixedly. The DRAM927is a memory that is used as a working area and the like of the CPU925, and temporarily holds OSs, programs, data to be processed, and the like. The CPU925, the flash memory926, and the DRAM927are connected to the internal bus928and access each other, thereby controlling the TV1as a whole. In addition, the CPU925is also connected to the expanded HDMI receiving unit923to control an IP communication process in the expanded HDMI receiving unit923.

The Ethernet (Registered Trademark) I/F929is connected to the Ethernet (Registered Trademark) terminal930to control IP communication with the server5and the like on the Internet6. Further, the Ethernet (Registered Trademark) I/F929is also connected to the high-speed data line I/F924to control IP signals input from the high-speed data line I/F924, as well as signals input from the Ethernet (Registered Trademark) terminal930.

The remote controller light receiving unit931receives control signals from the remote controller911operated by the user, and outputs the control signals to the CPU925. Accordingly, a control process of the TV1such as receiving and reproducing of content is performed in accordance with the control signals.

FIG. 24is a block diagram showing a structure of the PC4.

As shown inFIG. 24, the PC4includes a CPU941, a flash memory942, an S(Synchronous) DRAM943, a graphic processing unit944, a display panel945, a sound card946, a speaker947, an internal bus948, an external I/O (input/output) I/F949, an expanded HDMI transmitting unit950, an expanded HDMI terminal951, a high-speed data line I/F960, an Ethernet (Registered Trademark) I/F952, an Ethernet (Registered Trademark) terminal953, a wireless LAN I/F954, a USB I/F955, a USB terminal956, an ATA (Advanced Technology Attachment) I/F957, an HDD958, and an optical disc drive959.

The CPU941accesses the SDRAM943and the like when necessary, to perform overall control on each block of the PC4. Further, the CPU941also performs decoding processing of various encoded content. The flash memory942is a non-volatile memory in which firmware such as OSs and programs to be executed by the CPU925and various parameters is stored fixedly. The SDRAM943is a memory that is used as a working area of the CPU941and temporarily holds OSs, programs, data to be processed, and the like.

The graphic processing unit944renders video signals of various content, GUI screens during execution of OSs and applications, or the like to output the video signals to the display panel945formed of an LCD and the like. The sound card946generates audio signals during execution of various content, OSs, and applications to output the audio signals to the speaker947.

The CPU941, the flash memory942, the SDRAM943, the graphic processing unit944, and the sound card946are connected to the internal bus948, and further connected to the external I/O I/F.

Similar to the expanded HDMI terminal922in the TV1, the expanded HDMI terminal951is obtained by expanding a conventional HDMI terminal such that bidirectional data communication at high speed can be performed. The expanded HDMI transmitting unit950is connected to the AV amplifier2by the expanded HDMI terminal951via a HDMI cable, and inputs/outputs video signals and audio signals of various content and various other signals as baseband signals to and from the AV amplifier2and the TV1. The high-speed data line I/F960inputs, from the Ethernet (Registered Trademark) I/F929, signals to be output via the high-speed data line out of signals output from the expanded HDMI terminal951, and applies various signal processes to the input signals to output the processed signals to the expanded HDMI terminal951.

The Ethernet (Registered Trademark) I/F952is connected to the Ethernet (Registered Trademark) terminal953to control IP communication with the server5on the Internet6and IP communication by the HDMI terminal951using the high-speed data line I/F960.

The wireless LAN I/F954controls a communication process by wireless LAN. The USB I/F955is connected to the USB terminal956to control a USB communication process with various external apparatuses.

The ATA I/F957is connected to the HDD958and the optical disc drive959to connect each part of the PC4such as the CPU941to the HDD958and the optical disc drive959. The HDD958stores various programs such as OSs (Operating System) and applications, various contents, other data, and the like in a built-in hard disc, and reads the stored data. The optical disc drive959can be loaded with an optical disc (not shown), and can record various data on the optical disc and read the recorded data, in a similar way to that of the HDD958. Note that examples of the optical disc include a DVD (e.g., DVD-Video, DVD-RAM, DVD-R, DVD-RW, DVD+R, DVD+RW), a BD (Blu-ray Disc), a CD (Compact Disc), and the like.

Note that since the game apparatus3has a substantially similar structure to that of the PC4described above, the description thereof is omitted. Of course, the game apparatus3is different from the PC4in that it has software and hardware structures required for executing game applications.

FIG. 25is a diagram showing a basic electrical structure of the expanded HDMI transmitting unit950of the PC4and the expanded HDMI receiving unit923of the TV1. As described above, in this embodiment, the PC4functions as a source apparatus in HDMI and the TV1functions as a sink apparatus in HDMI. However, the configuration is not limited to this, and the functions as the source apparatus and as the sink apparatus may be interchanged between the apparatuses, or each apparatus may double as the source apparatus and the sink apparatus.

As shown inFIG. 25, the expanded HDMI transmitting unit950has a transmitting device120, and the expanded HDMI receiving unit923has a receiving device410. From the transmitting device120, video signals, audio signals and clock signals thereof are unidirectionally transmitted, and those signals are received by the receiving device410. For transmitting those signals, TMDS channels0to2and a TMDS clock channel in the TMDS method are used. The maximum transmission speed of the TMDS channels is about 5 Gbps, but not limited thereto.

A DCC140is used for the PC4as the source apparatus to read E-EDID from the TV1as the sink apparatus. E-EDID is profile information such as video and audio formats with which the sink apparatus is compatible, e.g., RGB, YCbCr 4:4:4, and YCbCr 4:2:2. The TV1as the sink apparatus has an EDIDROM (EDID ROM)160storing E-EDID. Note that, although not shown, similar to the TV1as the sink apparatus, the PC4as the source apparatus can also store E-EDID and transmit E-EDID to the TV1when necessary.

A CEC line130is used to perform bidirectional communication of control data between the PC4as the source apparatus and the TV1as the sink apparatus.

Incidentally, a conventional HDMI terminal is provided with a pin for an HPD (Hot Plug Detect) line and a pin for a reserved line as a signal line for a source apparatus to detect whether a sink apparatus is connected or not. For example, in HDMI of type A, the HPD pin is a pin having a pin number of19, and the reserved pin is a pin having a pin number of14.

As described above, in this embodiment, the HPD line and the reserved line are wired as a differential twist pair and expanded so as to function as a high-speed data line150capable of performing bidirectional IP communication by differential signals. In this embodiment, in the high-speed data line150, a pin corresponding to the conventional HPD pin is referred to as HPD/Ether+, and a pin corresponding to the conventional reserved pin is referred to as Reserve/Ether−.

As described above, the high-speed data line150is connected to the high-speed data line I/Fs (924,960) which are connected to the respective expanded HDMI terminals (22,51) of the TV1and the PC4, and is further connected to the Ethernet (Registered Trademark) I/Fs (929,952). The maximum transmission speed of the high-speed data line is about 100 Mbps, but not limited thereto.

In this embodiment, the TV1uses the high-speed data line150to transmit content incapable of being decoded to the source apparatus such as the PC4, and the PC4uses the TMDS channels to transmit the decoded content as a baseband signal.

Note that, in the example ofFIG. 25, the PC4is illustrated as the source apparatus, but of course the game apparatus3also has the expanded HDMI terminal and the above described high-speed data line I/F as well, and is capable of functioning as the source apparatus.

Next, a description will be made on an operation of the content decoding system structured as described above.

FIG. 26is a sequence diagram showing a process flow of the content decoding system in this embodiment. Further,FIG. 27is a flowchart showing a flow of an operation of the TV1as the sink apparatus in the content decoding system, andFIG. 28is a flowchart showing a flow of an operation of the game apparatus3and the PC4as the source apparatuses in the content decoding system.

First, in the TV1, a viewing request of content is input from a user using the remote controller911, by selecting a channel of digital broadcast, or inputting a reproducing request of content in the HDD958, for example ((61) inFIG. 26, Step81inFIG. 27). Then, the CPU925of the TV1judges whether the TV1can decode the content ((62) inFIG. 26, Step82inFIG. 27). If the CPU925judges that the content cannot be decoded (No in Step82), the CPU925transmits a query command that queries whether the game apparatus3and the PC A can decode the content to the game apparatus3and the PC4by the high-speed data line I/F24using the high-speed data line150of the expanded HDMI terminal922((63) inFIG. 26, Step83inFIG. 27).

FIG. 29are diagrams showing examples of the query command.

As shown inFIG. 29, in the query commands, data formats such as video, audio, and text, a stream format, an encoding format, a resolution, a bit rate, a sampling frequency, a sampling bit number, and the like are described as attributes of the content required to be decoded.FIG. 29(a) is an example of a command in requiring decoding of video content, andFIG. 29(b) is an example of a command in requiring decoding of audio content. InFIG. 29(a), decoding of video content encoded in MPEG4-AVC is the target of the query, and inFIG. 29(b), decoding of audio content encoded in an MP3 format is the target of the query. Note that the query commands are described in an XML (Extensible Markup Language) format, but not limited to this format.

In the game apparatus3and the PC4, the query command is received via the expanded HDMI terminal951and the high-speed data line I/F960(Step101inFIG. 28). Then, the CPU941of the game apparatus3and the PC4judges whether the game apparatus3and the PC4can decode the content that is the target of the query (Step102inFIG. 28).

If it is judged that the decoding is possible (Yes in Step102), the CPU941transmits a response command to the effect that the decoding is possible to the TV1via the high-speed data line150((66) inFIG. 26,106inFIG. 28). In this case, the CPU941calculates an expected processing time (delay time) for decoding the content, and responds with the response command also including the processing time.

If it is judged that the decoding is impossible (No in Step102), the CPU941make a query to the server5on the Internet6via the Ethernet (Registered Trademark) I/Fs52, as to whether software for decoding the content can be updated ((64) in FIG.26, Step103inFIG. 28). The CPU941receives responses to the query from the server5((65) inFIG. 26), and in accordance with the response results, judges whether the software can be downloaded (or updated) (Step104inFIG. 28). If it is judged that the download is possible (Yes in Step104), the CPU941downloads the software or its updated module (Step105inFIG. 28), and transmits via the high-speed data line150a response command to the effect that the content can be decoded through the download ((66) inFIG. 26, and Step106inFIG. 28). Further, if it is judged that the download is impossible in accordance with the response result (No in Step104), the CPU941transmits via the high-speed data lines150a response command to the effect that the content cannot be decoded ((66) inFIG. 26, Step110inFIG. 28).

FIG. 30are diagrams showing examples of the response commands described above.

FIG. 30(a) shows a response command in the case where the decoding is possible, which describes that the decoding is possible (yes) as a result of judging whether the decoding is possible, and the expected delay time for the decoding (10 ms).FIG. 30(b) shows a response command in the case where the decoding is impossible, which describes that the decoding is impossible (no) as a result of judging whether the decoding is possible.

Returning toFIG. 27, if a response command to the effect that the decoding is possible is not received from any apparatus (No in Step84), the CPU925of the TV1judges whether the TV1can download the software ((64) and (65) inFIG. 26, Step91inFIG. 27). If it is judged that the TV1cannot download the software, the CPU925transmits to the game apparatus3and the PC4via the high-speed data line150a command for requesting the game apparatus3and the PC4to make a query to the server5as to whether the downloaded is possible ((68) inFIG. 26, Step92inFIG. 27).

In accordance with the request from the TV1, the CPU941of the game apparatus3and the PC4makes a query to the server5as to whether the download is possible ((64) inFIG. 26, Step103inFIG. 28), and in accordance with a response result from the server5, transmits a response command that responds as to whether the decoding is possible to the TV1via the high-speed data line150((66) inFIG. 26, Step106and Step110inFIG. 28).

FIG. 31are diagrams showing examples of a command that queries the server5about whether the software can be downloaded, and a response command to the query command from the server5.FIG. 31(a) is an example of the query command that queries whether the download is possible, andFIG. 31(b) is an example of a response command about whether the download is possible.

As shown inFIG. 31(a), in the download query command, the decoding format of the content to be decoded (e.g., MP3 decoder) is described. As shown inFIG. 31(b), in the download response command, existence/nonexistence of software compatible with the decoding format of the content to be decoded and the location of the software (URL) are described. In each apparatus, the software is downloaded from the URL.

Returning toFIG. 27, if a response command to the effect that the decoding is possible is received (Yes in Step84), and if a response command to the effect that the decoding is possible through the download of the software is received (Yes in Step93), the CPU925of the TV1specifies an apparatus having the shortest processing time required for decoding, based on the response command ((69) inFIG. 26, Step75inFIG. 27). Then, the CPU925transfers the HDMI transmitting unit content to be decoded and a decoding request command thereof to the specified apparatus by the high-speed data line I/F24via the high-speed data line150((70) inFIG. 26and Step86inFIG. 27).

The CPU941of the game apparatus3and the PC4judges whether the transmission of the content along with the decoding request of the content is started (Step107inFIG. 28), and if the transmission of the content is started (yes), transmits one of <Image View On>, <Text View On>, and <Active Source> commands, which are input switching commands determined as transmission commands of the CEC line130, to the TV1via the CEC line130, to request the TV1to switch each input of the display panel18and the speaker21of the TV1to an input from the expanded HDMI terminal22((72) inFIG. 26, Step108inFIG. 28). Note that the <Image View On> command or the like is not limited to be transmitted by the CEC line130, and may be transmitted via the high-speed data line150, for example. The CPU941transmits the <Image View On> command or the like, and starts decoding the received content (Step109inFIG. 26). Then, the CPU941transmits the decoded content as a baseband signal to the TV1by the expanded HDMI transmitting unit950via the TMDS channels ((74) inFIG. 26, Step109inFIG. 28).

The CPU941of the TV1performs input switching to the expanded HDMI terminal922in accordance with the <Image View On> command or the like ((73) inFIG. 26, Step88inFIG. 27), and reproduces the decoded content received via the TMDS channels from the display panel918and the speaker921(Step90inFIG. 27).

Further, if the CPU925judges that the TV1can download the software (Yes in Step91inFIG. 27), the CPU925requests downloading of the software to the server5(Step92) and judges whether the target software exists at the URL (Step96). If it is judged that the software exists (Yes), the TV1downloads the software from the URL (Step97). Then, the CPU925decodes the content by the software (Step98), and reproduces the content from the display panel918and the speaker921(Step90).

Further, if it is judged that the software does not exist at the URL at Step96(No), and if there is no response to the effect that the content can be decoded through the download of the software from any apparatus at Step93(No), the CPU925displays on the display panel918that the content as the target of the user's viewing request cannot be reproduced because it cannot be decoded (Step94).

Note that, if it is judged that the content can be decoded by the TV1at Step82(Yes), the CPU925decodes (Step98) and reproduces (Step90) the content.

With the operation described above, even in the case where content incapable of being decoded by the TV1exists, it is possible to reproduce any content regardless of encoding formats by causing other apparatuses having decoding ability such as the game apparatus3and the PC4to decode the content, and by receiving the decoded content. Further, it is possible to promptly reproduce content without waiting time for a user's viewing request because the efficiency of the process from decoding to reproduction of content can be increased by using the high-speed data line150capable of performing bidirectional communication at high speed for communication of the query command such as the decoding request command with another apparatus and transmission of content, and by using the TMDS channels capable of transmitting large-volume data for transmission of the decoded content by a baseband signal.

The present invention is not limited to the embodiment described above, but various modifications can of course be made without departing from the gist of the present invention.

In the embodiment described above, the high-speed data line150(Ethernet (Registered Trademark)) in the expanded HDMI is used as the first transmission line used for communication of various commands regarding the content and the content decoding request, and the TMDS channels in expanded HDMI is used as the second transmission line used for transmission of the decoded content, but the first and second transmission lines are not limited thereto.

A USB (Universal Serial Bus), IEEE1394, and the like can also be used as the first transmission line, for example, and a DVI (Digital Visual Interface), a Display Port, a UDI (Unified Display Interface), and the like can also be used as the second transmission line, for example.

In the embodiments described above, the description is given on the case where it is required to decode the broadcast content received by the TV1and the content stored in the game apparatus3or the PC4as the content to be decoded, but the content to be decoded is not limited to such contents.

For example, there may be a case where, if a Web browser of the TV1is not compatible with Flash (Registered Trademark), the TV1transmits the Web page to the PC4via the high-speed data line150, and the PC4decodes the Web page and transmits the Web page to the TV1using the TMDS channels.

In addition, there may be a case where, for example, if the TV1is not compatible with decoding of audio content included in broadcast content and Web content, which is encoded in a new audio encoding format, e.g., an audio encoding format compatible with multi-channel surround, the TV1transmits the audio content to the game apparatus3and the PC4via the high-speed data lines150, and the game apparatus3and the PC4download software compatible with decoding of the audio content from the server5, decode the audio content using the software, and transmit the audio content to the AV amplifier2using the TMDS channels to output the audio content.

In the embodiment described above, the expanded HDMI terminal922of the TV1and the expanded HDMI terminal951of the PC4are wire-connected by the HDMI cable, but the both may be connected by wireless HDMI.

In the embodiments described above, the configuration in which the TV1, the AV amplifier2, the game apparatus3and the PC4are interconnected, but the configuration is not limited to those apparatuses, any electronic apparatus such as an HDD recorder, a DVD/BD player, and other AV apparatuses can be connected by HDMI, for example, to decode content.

DESCRIPTION OF REFERENCE NUMERALS