Abstract:
There is provided an IEEE 1394 transmitter for transmitting a plurality of audio data contents, having an audio data generator configured to sample the plurality of audio data contents sequentially to generate format data of an audio data content; and an IEEE 1394 transmission controller configured to add an IEEE 1394 header packet to the format data of the audio data content.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-066687 filed on Mar. 15, 2007, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The application relates to an IEEE (Institute of Electrical and Electronics Engineers) 1394 transmitter. 
     2. Description of the Related Art 
     Japanese Laid-open Patent Publication No. 2005-025270 discloses a technique for transmitting and receiving content using the IEEE 1394 standard. 
     SUMMARY 
     According to an aspect of an embodiment of the present invention, there is provided an IEEE 1394 transmitter for transmitting a plurality of audio data contents, comprising: an audio data generator configured to sample the plurality of audio data contents sequentially to generate format data of an audio data content; and an IEEE 1394 transmission controller configured to add an IEEE 1394 header packet to the format data of the audio data content. 
     The above-described embodiments of the present invention are intended as examples, and all embodiments of the present invention are not limited to including the features described above. 
     Additional advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an IEEE 1394 transmitter; 
         FIG. 2  is a diagram showing an IEEE 1394 packet; 
         FIG. 3  is a diagram showing a structure of an isochronous packet (ISO 1 ) of a first audio data content; 
         FIG. 4  is a diagram showing a structure of an isochronous packet (ISO 2 ) of a second audio data content; 
         FIG. 5  is a diagram showing a structure of an isochronous packet (ISO 3 ) of a third audio data content; 
         FIG. 6  is a block diagram showing an IEEE 1394 transmitter in accordance with an embodiment of the present invention; 
         FIG. 7  is a diagram showing a standard AM824 data format in accordance with an embodiment of the present invention; 
         FIG. 8  is a diagram showing a sub-label-attached AM824 data format in accordance with an embodiment of the present invention; 
         FIG. 9  is a diagram showing audio data content of eight channels in accordance with an embodiment of the present invention; 
         FIG. 10  is a timing chart of an encryption instruction signal ANGX in accordance with an embodiment of the present invention; 
         FIG. 11  is a diagram showing an isochronous packet header format in accordance with an embodiment of the present invention; 
         FIG. 12  is a diagram showing a CIP header format in accordance with an embodiment of the present invention; 
         FIG. 13  is a diagram showing an isochronous packet in accordance with the first embodiment; 
         FIG. 14  is a diagram showing an IEEE 1394 packet in accordance with the first embodiment; 
         FIG. 15  is a block diagram of an IEEE 1394 receiver in accordance with an embodiment of the present invention; and 
         FIG. 16  is a flowchart showing a process for decrypting audio data content in accordance with an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference may now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     When audio data of a plurality of contents is transmitted using the IEEE 1394 standard, for example, an IEEE 1394 packet is transmitted by an IEEE 1394 transmitter  100  shown in  FIG. 1  using the IEC (International Electrotechnical Commission) 61883-6 standard. 
     The IEEE 1394 transmitter  100  is configured to transmit three audio data contents each having eight channels. A first audio data content input from a three-wire interface is converted into parallel sampled audio data by a first phase-locked loop (PLL)  101  and a first serial-parallel converter, and is output to a first IEC 61883-6 encoder  104 . The first IEC 61883-6 encoder  104  attaches a label generated by a first label generator  103  to the sampled audio data, and outputs the label-attached sampled audio data to a first encryption unit  105 . The first encryption unit  105  encrypts the label-attached sampled audio data according to an output of an encryption controller  117 . The encryption controller  117  sets a level for encrypting the data to the first encryption unit  105  on the basis of an encryption setting signal ANG input from outside. 
     Second and third audio data contents are also processed in a similar manner. The resulting first, second, and third audio data contents are input to a selector  116 . The selector  116  selects one of the first to third audio contents, and outputs the selected content to an IEEE 1394 packet generator  118 . The IEEE 1394 packet generator  118  attaches a header to data of each of the first to third audio contents, and transmits an IEEE 1394 packet to the outside. 
       FIGS. 2 to 5  show an example in which a first audio data content of four channels, a second audio data content of two channels, and a third audio data content of two channels are transmitted by IEEE 1394 packet transmission. As shown in  FIG. 2 , an IEEE 1394 packet includes a cycle start packet (CS), an isochronous packet ISO 1  of the first audio data content shown in  FIG. 3 , an isochronous packet ISO 2  of the second audio data content shown in  FIG. 4 , and an isochronous packet ISO 3  of the third audio data content shown in  FIG. 5 . Each of the packets ISO 1  to ISO 3  has an isochronous header and a common isochronous packet (CIP) header attached to the top thereof. Therefore, the IEEE 1394 transmitter  100  transmits an IEEE 1394 packet in which the isochronous header and the CIP header are attached to data of each audio data content. 
     However, when audio data contents of a plurality of channels are transmitted and received via an IEEE 1394 interface, a header is attached to each of the audio data contents. As a result, an overhead of an IEEE 1394 packet increases. Therefore, it is desirable to reduce the overhead of a packet when audio contents of a plurality of channels are transmitted and received via an IEEE 1394 interface. 
       FIG. 6  is a block diagram of an IEEE 1394 transmitter  1  according to a first embodiment of the present invention. The IEEE 1394 transmitter  1  converts up to  24  audio data contents input via a three-wire interface into an IEEE 1394 packet, encrypts the packet according to setting, and transmits the encrypted packet to an IEEE 1394 bus. 
     The IEEE 1394 transmitter  1  includes a serial-parallel converter  2 , a PLL  3 , an IEC 61883-6 encoder  4 , a label generator  5 , an encryption unit  6 , an IEEE 1394 transmission controller  7 , an sy parameter setting unit  8 , and an encryption controller  9 . 
     The serial-parallel converter  2  converts up to  24  audio data contents input via the three-wire interface into parallel sampled audio data. 
     The IEEE 1394 transmitter  100  shown in  FIG. 1  includes three PLLs, namely, the first PLL  101 , the second PLL  106  and the third PLL  111 . The IEEE 1394 transmitter  1  according to the first embodiment includes a single PLL, namely, the PLL  3 . The IEEE 1394 transmitter  1  can receive audio data contents using a common clock. Since only one PLL is required for clock control in the IEEE 1394 transmitter  1 , the number of terminals of clocks can be reduced and a power consumption of the PLL can also be reduced. 
     The IEC 61883-6 encoder  4  and the label generator  5  convert the sampled audio data into audio data complying with the IEC 61883-6 format. 
       FIG. 7  shows a standard AM824 data format. The individual sampled audio data is converted to the standard AM824 data format in the IEC 61883-6 format by attaching a label.  FIG. 8  shows a sub-label-attached AM824 data format. In the sub-label-attached AM824 data format in the IEC 61883-6 format, two labels, i.e., a label and a sub-label, are attached to the top of data. 
       FIG. 9  shows audio data content of eight channels. The audio data content of eight channels is composed of two quadlets of sub-label-attached AM824 data at the top thereof, followed by standard AM824 data for the eight channels. Ancillary Data included in the sub-label-attached AM824 data contains information relating to the audio data content, such as compression information of the audio data content. 
     The encryption unit  6  encrypts the AM824 data output from the IEC 61883-6 encoder  4  using the 5C-DTCP (5 Company Digital Transmission Content Protection) protocol according to an encryption instruction signal ANGX output from the encryption controller  9 . The encryption controller  9  outputs the encryption instruction signal ANGX on the basis of an encryption signal ANG input from outside. 
       FIG. 10  is a timing chart of the encryption instruction signal ANGX output from the encryption controller  9 . The two sets of Ancillary Data (in  FIG. 10 , ANC 1  and ANC 2 ) placed at the top of the AM824 data are encrypted using a sy parameter with the highest restrictiveness. The data of channels to be encrypted (in  FIG. 10 , CH 5  and CH 6 ) is encrypted according to the encryption signal ANG. 
     The copy levels include, in ascending order of restrictiveness, copy-free, copy-one-generation, and copy-never. The sy parameter setting unit  8  sets the sy parameter to the highest-restrictiveness copy level based on the encryption instruction signal ANGX. 
     Specifically, when the encryption instruction signal ANGX includes copy-free only, the sy parameter is set to copy-free. When the encryption instruction signal ANGX includes copy-one-generation but does not include copy-never, the sy parameter is set to copy-one-generation. When the encryption instruction signal ANGX includes copy-never, the sy parameter is set to copy-never. Accordingly, the sy parameter is set to the highest-restrictiveness copy level based on the encryption instruction signal ANGX. 
     The IEEE 1394 transmission controller  7  attaches the isochronous header and the CIP (Common Isochronous Packet) header to the top of the IEC 61883-6 format data output from the encryption unit  6 , and transmits an entire isochronous packet to the external IEEE 1394 bus. 
       FIG. 11  shows an isochronous packet header format. A “data_length” parameter indicates the number of bytes in the entire isochronous packet. The “data_length” parameter is set to an arbitrary value. A “tag” parameter indicates that the packet contains the CIP header, and is set to a fixed value of 01. A “channel” parameter indicates a channel number used to identify the isochronous packet, and is set to an arbitrary value. A “tcode” parameter is a code indicating the type of the packet, and is set to value 1010 in the case of an isochronous packet. An sy parameter contains copy information in the audio format. 
       FIG. 12  shows a CIP header format. A source-node-ID (SID) parameter indicates an ID of a source node that transmits the packet. The SID parameter is set to an arbitrary value. A data-block-size (DBS) parameter indicates the size of one divided data block, and is set to an arbitrary value. A fraction-number (FN) parameter indicates the number of data blocks into which one source packet is divided. Since the IEEE 1394 transmitter  1  does not divide a source packet, the FN parameter is set to a fixed value of 00. A quadlet-padding-count (QPC) parameter indicates the number of quadlets added for the division (a quadlet represents a data sequence of four bytes). 
     Since the IEEE 1394 transmitter  1  does not perform the division, the QPC parameter is set to a fixed value of 000. A source-packet-header (SPH) parameter indicates whether or not a source packet header has been attached. Since the IEEE 1394 transmitter  1  does not attach a source packet header, the SPH parameter is set to a fixed value of 0. An Rsv parameter is an extension region for future use. 
     In the IEEE 1394 transmitter  1 , the Rsv parameter is set to a fixed value of 00. A data-block-continuity-counter (DBC) parameter indicates a continuity counter value of a data block, and is incremented by +1 each time one data block is transmitted. A format (FMT) parameter indicates a format type of data of the packet. Since the IEEE 1394 transmitter  1  handles an audio and music format, the FMT parameter is set to a fixed value of 010000. A format-dependent-field (FDF) parameter is a field depending on format, and is set to an arbitrary value. A time stamp value is set in an SYT parameter. 
       FIG. 13  shows a structure of an isochronous packet transmitted from the IEEE 1394 transmitter  1  according to the first embodiment. The isochronous packet is composed of an isochronous packet header, a CIP header, IEC 61883-6 data, and a CRC of the data. In the IEC 61883-6 data, the data of channels  5  and  6  is encrypted data, and therefore, the label of the data of channels  5  and  6  has a value other than 4X (expressed in hexadecimal notation, the same applies to the following description). The sub-label-attached AM824 format packet including Ancillary Data regarding channels  5  and  6  is also an encrypted packet. The sy parameter in the isochronous packet header is also set to the value corresponding to the level for encryption. 
       FIG. 14  shows an IEEE 1394 packet transmitted from the IEEE 1394 transmitter  1  according to the first embodiment. The IEEE 1394 packet is generated by inserting a cycle start packet (CS) before the isochronous packet structure (ISO) shown in  FIG. 13 , and is transmitted from the IEEE 1394 bus. 
     The IEEE 1394 transmitter  1  according to the first embodiment transmits audio data content of a plurality of channels through a single content packet. Therefore the IEEE 1394 transmitter  1  according to the first embodiment can handle a packet having a single header portion, and the overhead of the IEEE 1394 packet can be reduced. 
       FIG. 15  is a block diagram of an IEEE 1394 receiver  10  according to an embodiment of the present invention. The IEEE 1394 receiver  10  receives a packet from an IEEE 1394 bus, and transmits audio content to outside via a three-wire interface. 
     The IEEE 1394 receiver  10  includes an IEEE 1394 reception controller  11 , a first determination unit  12 , a second determination unit  13 , a first decryption unit  14 , a third determination unit  15 , a second decryption unit  16 , a selector  17 , a decryption controller  18 , an IEC 61883-6 decoder  19 , a PLL  20 , and a parallel-serial converter  21 . 
     The IEEE 1394 reception controller  11  reads, from the packet transmitted from the IEEE 1394 bus, the sy parameter included in the isochronous packet header and the standard AM824 format data included in the IEC 61883-6 data, including the data channels, quadlet-by-quadlet. 
     The first determination unit  12  determines the copy level of the sy parameter, i.e., copy-free, copy-one-generation, or copy-never. The determination result is output to the decryption controller  18 . 
     The second determination unit  13  receives a label in a quadlet of standard AM824 format data including a data channel read by the IEEE 1394 reception controller  11 , and determines whether or not the label has a value of 4X. The determination result is output to the decryption controller  18 . 
     The first decryption unit  14  decrypts the quadlet of data read by the IEEE 1394 reception controller  11  using the sy parameter. The decrypted data is output to an input terminal IN 1  of the selector  17 . The label in the decrypted data is output to the third determination unit  15 . 
     The third determination unit  15  receives the label in the AM824 format data decrypted by the first decryption unit  14 , and determines whether or not the label has a value of 4X. The determination result is output to the decryption controller  18 . 
     The second decryption unit  16  decrypts the quadlet of data read by the IEEE 1394 reception controller  11  using a parameter other than the sy parameter. The decrypted result is output to an input terminal IN 2  of the selector  17 . 
     The quadlet of data read by the IEEE 1394 reception controller  11  is input to an input terminal IN 0  of the selector  17 . The output from the first decryption unit  14  is input to the input terminal IN 1  of the selector  17 . The output from the second decryption unit  16  is input to the input terminal IN 2  of the selector  17 . One of the signals input to the input terminals IN 0  to IN 2  is selected according to an output of the decryption controller  18 , and is output to the IEC 61883-6 decoder  19 . 
     The decryption controller  18  outputs a selection signal to the selector  17  according to the procedure for decrypting each audio data content on the basis of the determination signals output from the first determination unit  12 , the second determination unit  13 , and the third determination unit  15 . 
     The IEC 61883-6 decoder  19 , based on the audio data content separation information, which is a data removed the label from the AM824 format data output from the selector  17  and is input from an external device (not shown), outputs the audio data content to the parallel-serial converter  21 . 
     The PLL  20  and the parallel-serial converter  21  output up to  24  audio data contents output from the IEC 61883-6 decoder  19  via a three-wire interface from data terminals SD 00  to SD 23  in synchronization with a common clock signal LRCK and a clock signal BCLK. 
     The IEEE 1394 receiver  10  according to the second embodiment is configured such that the single PLL  20  is used to transmit audio data using a common clock. In the IEEE 1394 receiver  10 , therefore, only one PLL is required for clock control. As a result, the number of terminals of clocks can be reduced and a power consumption of the PLL can also be reduced. 
       FIG. 16  is a flowchart showing a process for decrypting audio data content. 
     In operation S 1 , the first determination unit determines whether the sy parameter indicates copy-free, copy-one-generation, or copy-never. If the sy parameter indicates copy-free, the process proceeds to operation S 3 . If the sy parameter indicates copy-one-generation or copy-never, the process proceeds to operation S 2 . 
     In operation S 2 , the second determination unit determines whether a label in a quadlet of standard AM824 format data including a data channel read by the IEEE 1394 reception controller  11  has a value of 4X or any other value. If the label has a value of 4X, the process proceeds to operation S 3 . If the label has a value other than 4X, the process proceeds to operation S 4 . 
     In operation S 3 , the decryption controller outputs a selection signal for selecting the signal at the input terminal IN 0  of the selector. Then, the decryption process ends. 
     In operation S 4 , the first decryption unit decrypts the quadlet of standard AM824 format data including the data channel read by the IEEE 1394 reception controller using the sy parameter. Then, the process proceeds to operation S 5 . 
     In operation S 5 , it is determined whether the label in the AM824 format data decrypted in operation S 4  has a value of 4X or a value other than 4X. If the label has a value of 4X, the process proceeds to operation S 6 . If the label has a value other than 4X, the process proceeds to operation S 7 . 
     In operation S 6 , the decryption controller outputs a selection signal for selecting the signal at the input terminal IN 1  of the selector. Then, the decryption process ends. 
     In operation S 7 , the second decryption unit decrypts the quadlet of standard AM824 format data including the data channel read by the IEEE 1394 reception controller using a value other than the sy parameter (e.g., copy-one-generation if the sy parameter indicates copy-never, or copy-never if the sy parameter indicates copy-one-generation). Then, the process proceeds to operation S 8 . 
     In operation S 8 , the decryption controller outputs a selection signal for selecting the signal at the input terminal IN 2  of the selector. Then, the decryption process ends. 
     The process according to the flowchart shown in  FIG. 16  ensures that each audio content encrypted with copy-one-generation or copy-never can be decrypted. 
     The IEEE 1394 receiver  10  according to the second embodiment receives audio data content of a plurality of channels through a single content packet. Therefore, the IEEE 1394 receiver  10  according to the second embodiment can handle a packet having a single header portion, and the overhead of the IEEE 1394 packet can be reduced. 
     Embodiments of the present invention are not limited to the first or second embodiment, and it is to be understood that a variety of improvements and modifications can be made without departing from the scope of the invention. 
     The first and second embodiments provide an IEEE 1394 transmitter and IEEE 1394 receiver having a three-wire interface for transmitting and receiving audio data content of up to 24 channels. However, embodiments of the present invention are not limited to the first or second embodiment, and can also provide an IEEE 1394 transmitter and IEEE 1394 receiver having a three-wire interface for transmitting and receiving audio data content of a smaller number of channels such as eight channels. 
     Example embodiments of the present invention have now been described in accordance with the above advantages. It will be appreciated that these examples are merely illustrative of the invention. Many variations and modifications will be apparent to those skilled in the art. 
     Although a few preferred embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.