Abstract:
Disclosed are a multimedia device controller, a source device, a sink device and a transmission system that can manage multimedia devices capable of simultaneous output of video and audio from multiple Blu-ray discs or the like. A master device ( 110 ) references a source/sink device function management table ( 200 ) and a band management table ( 300 ) and controls the video and audio bands for the source and sink devices during transmission of multiple video and audio signals. When a band that is kept is changed, the master device ( 110 ) also confirms the status of a transmission path ( 100 ) and the content usage conditions of sink devices ( 140, 150 ) and controls the band. For example, when the master device ( 110 ) outputs two sets of video and audio in one set, the band is changed to one band in which the two sets of video and audio are synthesized.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a multimedia device control apparatus, a source device, a sink device and a transmission system for controlling a plurality of multimedia devices. 
       BACKGROUND ART 
       [0002]    Heretofore, in a system to provide multimedia information according to user request, a wide frequency band is used, and audio, images, characters and so on are allocated on a per band basis, to transmit a plurality of information items at the same time. 
         [0003]    With a multimedia information providing apparatus used in a vehicle, the frequency band that can be used is limited. In this limited transmission frequency band, transmission band needs to be managed properly in order to transmit a plurality of multimedia information items. 
         [0004]    Patent literature 1 discloses a band management apparatus that checks the maximum bandwidth, minimum bandwidth and priority when a master device checks the band between a source device and a sink device. When a channel has a capacity to secure the maximum bandwidth, the apparatus disclosed in patent literature 1 secures the maximum bandwidth, or, when a channel cannot secure the maximum bandwidth, the apparatus reduces a bandwidth that is already kept or releases a band of lower priority free. By this means, provision is made for a plurality of devices to be able to make optimal use of a channel. 
         [0005]      FIG. 1  is a block diagram showing a configuration of a multimedia device control system used in a vehicle-mounted environment. 
         [0006]    As shown in  FIG. 1 , in a multimedia device control system, master device  11 , a plurality of source device  12  and  13  (source devices A and B) and a plurality of sink devices  14  and  15  (sink devices A and B) are connected to channel  10 . 
         [0007]    Source devices A and B are video/audio output devices. Sink devices A and B are video/audio input devices. For example, as a vehicle-mounted electronic device, there is a display apparatus that displays images recorded in a recording medium such as a CD-ROM and a DVD or television broadcasting and similar images using an LCD or suchlike display, like a navigation system, a DVD (Digital Versatile Disc) player and a television receiver. 
         [0008]    Channel  10  is represented by a network that is capable of transmitting arbitrary video, audio and control signals. Examples of protocols include the MOST (Media Oriented Systems Transport) standard (hereinafter “MOST”) and IEEE (Institute of Electrical and Electronics Engineers) 1394 High Performance Serial Bus (hereinafter “IEEE1394”). 
         [0009]    Master device  11  manages audio and transmission in respect to devices connected to channel  10  (in this case, source devices A and B and sink devices A and B). To be more specific, master device  11  establishes audio and video transmission band between source devices and sink devices and performs a control and management. 
         [0010]      FIG. 2  shows band management table  20  which master device  11  uses to manage source devices A and B and sink devices A and B. 
         [0011]    As shown in  FIG. 2 , band management table  20  stores a band connecting device and bandwidth per band management ID number. In  FIG. 2 , for example, referring to band management ID number  1 , source device A and sink device A are stored as band connecting devices, and a bandwidth of 10 Mbps of channel  10  is stored. Also, referring to band management ID number  2 , source device B and sink device B are stored as band connecting devices and a bandwidth of 5 Mbps of channel  10  is stored, and, referring to band management ID number  3 , source device A and sink device B are stored as band connecting devices and a bandwidth of 5 Mbps of channel  10  is stored. The combination of source device A and sink device A associated with band management ID number  1  requires the maximum bandwidth. 
         [0012]    In a vehicle-mounted environment, a plurality of source devices A and B and a plurality of sink devices A and B are present, and also master device  11  to control these devices is present. Channel  10  connects between these devices. When video and audio are transmitted and received, transmission band is secured between source devices A and B and sink devices A and B, and video and audio are transmitted in that transmission band. Master device  11  manages transmission band based on band management table  20 . 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1: Japanese Patent Application Laid-Open No. 2000-115198 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0014]    With a conventional vehicle-mounted multimedia device control apparatus, master device  11  performs a control every time one band is secured. In this case, the bandwidth is reduced, or a band of lower priority is released free, regardless of the relationships between a plurality of bands already kept on channel  10 . 
         [0015]    In conventional vehicle-mounted device communication, the video or audio of one content item provides only one output stream from one source device. For example, with conventional DVD or similar content, there is only one video output stream and one audio output stream for every one content item. Consequently, master device  11  does not have to consider the relationships between a plurality of bands. 
         [0016]    However, for a vehicle-mounted multimedia device, introducing a blu-ray disc (BD) has the following problem. 
         [0017]    With a BD, there are functions for outputting two streams of video and audio per content item at the same time, such as a bonus view picture-in-picture (“PinP”) function. These two streams of video and audio data are related, so that a master device requires a system for managing a plurality of bands for two streams of video and audio data per content item and performing a band control based on the relationships between a plurality of bands. 
         [0018]    Also, depending on the performance of source devices and sink devices, there are devices that cannot transmit and receive two streams of band. Consequently, a master device has to determine a transmission means for two streams of video and audio data based on the transmission functions of source devices and the reception functions of sink devices, and perform a band control. 
         [0019]    It is therefore an object of the present invention to provide a multimedia device control apparatus, a source device, a sink device and a transmission system to manage a multimedia device that can output a plurality video and audio data items at the same time such as a BD. 
       Solution to Problem 
       [0020]    A multimedia device control apparatus according to the present invention comprises a channel and a multimedia device which is to be connected to the channel and which is capable of outputting a plurality of video and audio data items at the same time, and controls the multimedia device by controlling a band of the channel, and this multimedia device control apparatus has: a function management table that manages a function of the multimedia device; a band management table that manages a state of a band kept by the multimedia device; and a band control section that, when a plurality of video and audio data items are transmitted, controls video and audio bands, for the multimedia device, with reference to the function management table and the band management table. 
         [0021]    A source device according to the present invention is to be connected to a multimedia device control apparatus via a channel and is capable of outputting a plurality of video and audio data items at the same time, and this source device receives a device control signal from the multimedia device control apparatus and performs transmission using a band specified by the control signal. 
         [0022]    A sink device according to the present invention is connected to a multimedia device control apparatus via channel and is capable of outputting a plurality of video and audio data items at the same time, and this sink device receives a device control signal from the multimedia device control apparatus and performs reception using a band specified by the control signal. 
         [0023]    A transmission system according to the present invention comprises a channel, a multimedia device that is connected to the channel and that is capable of outputting a plurality of video and audio data items at the same time, and a multimedia device control apparatus that manages the multimedia device by managing a band of the channel, and, in this transmission system, the multimedia device control apparatus has: a function management table that manages a function of the multimedia device; a band management table that manages a state of a band kept by the multimedia device; and a band control section that, when a plurality of video and audio data items are transmitted, controls video and audio bands, for the multimedia device, with reference to the function management table and the band management table. 
       Advantageous Effects of Invention 
       [0024]    The present invention makes it possible to manage a multimedia device that can output a plurality of video and audio data items at the same time, such as a BD. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0025]      FIG. 1  is a block diagram showing a configuration of a multimedia device control system used in a vehicle-mounted environment; 
           [0026]      FIG. 2  shows a band management table which a master device uses to manage source devices A and B and sink devices A and B; 
           [0027]      FIG. 3  is a block diagram showing a configuration of a multimedia device control system according to an embodiment of the present invention; 
           [0028]      FIG. 4  shows an example of source/sink device function management table according to the above embodiment; 
           [0029]      FIG. 5  is a flowchart showing processing in a master device in a multimedia device control system according to the above embodiment on an overall scale; 
           [0030]      FIG. 6  is a control stream diagram for explaining source/sink device function check processing in a multimedia device control system according to the above embodiment; 
           [0031]      FIG. 7  is a flowchart showing band securing processing in a multimedia device control system according to the above embodiment; 
           [0032]      FIG. 8  shows one example of a band management table in a multimedia device control system according to the above embodiment; 
           [0033]      FIG. 9  is a flowchart showing band change processing in a multimedia device control system according to the above embodiment; 
           [0034]      FIG. 10  is a control stream diagram for explaining a method of using content by a multimedia device control system according to the above embodiment; 
           [0035]      FIG. 11  shows one example of a content use management table in a multimedia device control system according to the above embodiment; 
           [0036]      FIG. 12  shows one example of a band management table in the event a band is changed, in a multimedia device control system according to the above embodiment; and 
           [0037]      FIG. 13  is a flowchart showing band release processing in a multimedia device control system according to the above embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0038]    Now, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiment 
       [0039]      FIG. 3  is a block diagram showing a configuration of a multimedia device control system according to an embodiment of the present invention. 
         [0040]    In the multimedia device control system of  FIG. 3 , master device  110 , source device  120  (source device &lt;1&gt;), source device  130  (source device &lt;2&gt;), sink device  140  (sink device &lt;1&gt;) and sink device  150  (sink device &lt;2&gt;), are connected to channel  100 . These devices can communicate with each other. 
         [0041]    Source devices  120  and  130  are video/audio output devices. Sink devices  140  and  150  are video/audio input devices. For example, source device  120  is a BD that provides two-stream transmission content, and source device  130  is a DVD player. This is one example, and a navigation system, a DVD player or a television receiver may be used as a vehicle-mounted electronic device. 
         [0042]    Channel  100  is a network that is capable of transmitting arbitrary video and audio control signals based on, for example, MOST and IEEE1394. 
         [0043]    Master device  110  manages audio and video transmission in respect to source devices  120  and  130  and sink devices  140  and  150  connected to channel  100 . Master device  110  manages a plurality of bands for two streams of video and audio data per content item. 
         [0044]    Before securing bands, master device  110  checks the performance of source devices  120  and  130  and sink devices  140  and  150  and secures bands to suit the performance of devices. 
         [0045]    Master device  110 , when changing a band that is kept, checks the state of channel  100  and the situation of use of content by sink devices  140  and  150 , and performs a band control. 
         [0046]    Master device  110  has processing section  111 , memory section  112 , and communication control section  113 . 
         [0047]    Processing section  111  performs processing related to master device  110 . Processing related to master device  110  includes all processing performed according to this embodiment. Examples include channel band management processing, retaining and reading processing with memory section  112  in each management tale. Other examples include processing of requesting processing to communication control section  113  when there is a command request and response to a sink device. 
         [0048]    Memory section  112  memorizes source/sink device function management table  200  for managing the performance and functions of source devices  120  and  130  and sink devices  140  and  150  (see  FIG. 4 ). To be more specific, with source devices  120  and  130 , the function refers to the number of output streams in which each device is able to output video and audio per content item at the same time. Likewise, with sink devices  140  and  150 , the function refers to the number of input streams in which each device is able to receive as input video and audio per content item at the same time. 
         [0049]    Furthermore, memory section  112  holds processing data on a temporary basis. Source/sink device function management table  200  (see  FIG. 4 ) manages the state of band kept between all devices on channel  100 . Source/sink device function management table  200  is updated by the source/sink device function check processing of  FIG. 6  (described later). 
         [0050]    Furthermore, memory section  112  stores band management table  300  (see  FIG. 8 ) and content use management table  400  (see  FIG. 11 ). Band management table  300  manages the state of bands kept by source devices  120  and  130  and sink devices  140  and  150 . Also, content use management table  400  manages the situation of use of content by source devices  120  and  130  and sink devices  140  and  150 . 
         [0051]    Communication control section  113  communicates on channel  100 . 
         [0052]    Source device  120  has processing section  121 , data output section  122 , and communication control section  123 . Source device  130  has processing section  131 , data output section  132 , and communication control section  133 . 
         [0053]    Processing sections  121  and  131  perform processing related to source devices  120  and  130 . Processing related to source devices  120  and  130  includes all processing performed according to this embodiment. Examples include processing of reporting information about a device check request from master device  110 , via communication control sections  123  and  133 . Other examples include processing of requesting a playback, stop and so on, to data output sections  122  and  132 . Other examples include processing of reporting a band securing or releasing request from master device  110  to communication control sections  123  and  133  and performing a control. 
         [0054]    Data output section  122  and  132  output video and audio content. 
         [0055]    Communication control sections  123  and  133  secure bands allocated by master device  110  and communicate on channel  100 . 
         [0056]    Sink device  140  has processing section  141 , data input section  142  and communication control section  143 . Sink device  150  has processing section  151 , data input section  152  and communication control section  153 . 
         [0057]    Processing sections  141  and  151  perform processing related to sink devices. Processing related to sink devices cover all processing performed according to the present embodiment, including processing of reporting information via communication control sections  143  and  153  about a device check request and content use request from master device  110 , processing of requesting start and stop to data input section  142  and  152 , and processing of reporting a band connecting/disconnecting request from master  110  to communication control sections  143  and  153  and performing a control. 
         [0058]    Data input sections  142  and  152  receive as input video and audio content. 
         [0059]    Communication control sections  143  and  153  secure bands by means of master device  110 , connect with the bands of the source devices, and communicate on channel  100 . 
         [0060]      FIG. 4  shows an example of source/sink device function management table  200 . 
         [0061]    As shown in  FIG. 4 , source/sink device function management table  200  stores transmission functions and reception functions on a per device type basis. In the example of  FIG. 4 , for example, with source device  120  (source device &lt;1&gt;), the transmission function is “two-stream output” and the reception function is “none.” Source device  120  (source device &lt;1&gt;) is, for example, a BD. Also, source device  120  (source device &lt;1&gt;) is applicable to a case where a user makes selection from the two-stream output of a terrestrial digital broadcast tuner. Sink device  140  (sink device &lt;1&gt;) is, for example, a rear display, a headphone amplifier or a similar device. Source device  130  (source device &lt;2&gt;) is, for example, a DVD. Sink device  150  (sink device &lt;2&gt;) is, for example, an audio amplifier. 
         [0062]    In  FIG. 4 , source device  120  (source device &lt;1&gt;) is capable of outputting two streams, and sink device  140  (sink device &lt;1&gt;) is capable of receiving two streams as input. Also, source device  130  (source device &lt;2&gt;) is capable of outputting one stream, and sink device  150  (sink device &lt;2&gt;) is capable of receiving one stream as input. 
         [0063]    Now, the operations of a multimedia device control system configured as described above will be described. 
         [0064]    [Overall Processing] 
         [0065]      FIG. 5  is a flowchart showing processing of master device  110  on an overall scale. In this figure, “S” stands for “step.” 
         [0066]    In step S 1 , master device  110  carries out “source/sink device function check processing” for checking the functionality conditions of source devices and sink devices (see  FIG. 6 ). For example, in a vehicle-mounted multimedia device control system, shortly after a user turns on an engine and powers on an electronic device, master device  110  checks whether or not the source and sink devices can transmit BD content, before the source and sink devices transmit video and audio. 
         [0067]    In step S 2 , master device  110  decides whether or not to start transmission from source devices  120  and  130 . This start of transmission is decided based upon whether or not to transmit BD content. 
         [0068]    If source devices  120  and  130  do not start transmitting video and audio (that is, if source devices  120  and  130  do not start transmitting BD content), the step moves to step S 3 , and, if source devices  120  and  130  start transmitting video and audio content (that is, if source devices  120  and  130  start transmitting BD content), the step moves to step S 4 . 
         [0069]    In step S 3 , master device  110  decides whether not to stop video and audio transmission in an arbitrary source device. When not stopping video and audio transmission in an arbitrary source device, master device  110  does not do anything, and the step returns to above step S 2 . In this case, step S 2  ad step S 3  form an infinite loop. 
         [0070]    In step S 4 , master device  110  performs band securing processing (see  FIG. 7 ). 
         [0000]    In this band securing processing, master device  110  looks at the functions of source/sink devices, and secures two streams of band when a source/sink device is capable of transmitting two streams of band, or secures one stream of band when a source/sink device is not capable of transmitting two streams of band. The details of band securing processing will be described using  FIG. 7 . 
         [0071]    In step S 5 , master device  110  decides whether or not to change channel  100  for the source devices from two streams to one stream, from two streams to zero, or from one stream to zero, based on user operation. 
         [0072]    If video and audio transmission stops in an arbitrary device in above step S 3 , or when channel  100  changes from two streams to one stream, from two streams to zero or from one stream to zero in above step S 5 , the step moves to step S 6 . 
         [0073]    In step S 6 , master device  110  performs band release processing and moves back to above step S 2 . 
         [0074]    If in above step S 5  channel  100  does not change from two streams to one stream, from two streams to zero or from one stream to zero, the step moves to step S 7 . 
         [0075]    In step S 7 , master device  110  decides whether or not to stop video and audio transmission in another source device. 
         [0076]    If another source device does not transmit video and audio, the step returns to above step S 5 . 
         [0077]    If another source device transmits video and audio, in step S 8 , master device  110  performs band change processing (see  FIG. 10 ), and the step returns to above step S 5 . 
         [0078]    [Source/Sink Device Function Check Processing] 
         [0079]      FIG. 6  is a stream diagram for explaining “source/sink device function check processing” of step S 1  in  FIG. 5 . 
         [0080]    As shown in  FIG. 6 , master device  110  issues a function check request to all of source devices  120  and  130  connected to channel  100  (see S 11 ). This function check request is not a general check request/check response which a master device  110  issues to acquire information relate to source devices and sink devices, and is a check request/check response that is issued in order to acquire information required upon transmitting BD content in two streams or in one stream. To be more specific, this function check request is a request to check whether two streams or one stream can be transmitted using a BD. 
         [0081]    Source devices  120  and  130  having received a function check request transmit function check responses to master device  110  (see S 12 ). These function check responses answer whether source devices  120  and  130  use two BD streams or one BD stream, at the time source devices  120  and  130  receive the above function check request. 
         [0082]    Master device  110  updates source/sink device function management table  200  (see  FIG. 4 ) held in memory section  112  (see  FIG. 3 ) of master device  110 , based on the function check responses from source devices  120  and  130  (see S 13 ). 
         [0083]    Master device  110  issues a function check request to all of sink devices  140  and  150  connecting with channel  100  (see S 14 ). 
         [0084]    Sink devices  140  and  150  having received a function check request transmit function check responses to master device  110  (see S 15 ). 
         [0085]    Master device  110  updates source/sink device function management table  200  (see  FIG. 4 ) held in memory section  112  (see  FIG. 3 ) of master device  110 , based on the function check responses from sink devices  140  and  150  (see S 16 ). 
         [0086]    Master device  110  thus checks functions of source and sink devices on channel  100 , and, based on function check responses acquired as a result of the checking, updates source/sink device function management table  200  (see  FIG. 4 ) in memory section  112  (see  FIG. 3 ). In  FIG. 4 , source device  120  (source device &lt;1&gt;) supports two-stream output, sink device  140  (sink device &lt;1&gt;) supports two-stream input, source device  130  (source device &lt;2&gt;) supports one-stream output and sink device  150  (sink device &lt;2&gt;) supports one-stream input. 
         [0087]    Before securing bands, master device  110  checks the performance of source devices and sink devices, and secures bands to suit the performance of these devices. Consequently, the above-described source/sink device function check processing is carried out first when master device  110  secures a transmission band, mode in which this processing is performed at appropriate timing, is also possible. 
         [0088]    [Band Securing Processing] 
         [0089]      FIG. 7  is a flowchart showing band securing processing. This is a detailed flow of “band securing processing” of step S 4  in  FIG. 5 . 
         [0090]    In step S 21 , master device  110  decides whether or not two-stream transmission content is transmitted. In this embodiment, two-stream transmission content is BD content. Master device  110  decides whether BD content is two-stream transmission content or one-stream transmission content. 
         [0091]    In the event of two-stream transmission content, in step S 22 , master device  110  checks source/sink device function management table  200 . 
         [0092]    In step S 23 , master device  110  decides whether or not source devices  120  and  130  are capable of two-stream transmission, with reference to source/sink device function management table  200 . 
         [0093]    If at least one of source devices  120  and  130  is capable of two-stream transmission, in step S 24 , master device  110  decides whether or not source devices  120  and  130  are capable of two-stream reception, with reference to source/sink device function management table  200 . 
         [0094]    If at least one of sink devices  120  and  130  is capable of two-stream reception, the step moves to step S 25 . In step S 25  and step S 26 , master device  110  selects source devices and sink devices depending on the performance of source devices and sink devices (two streams or one stream). 
         [0095]    Now, this stream ( FIG. 7 ) is not intended to select a device, for which and to which a band is kept or connected, based on the performance of source devices and sink devices (two streams or one stream). This stream checks, with each device, which functionality of two-streams and one-stream that device supports, with reference to source/sink device function management table  200  of  FIG. 4 , and secures a band to suit that device&#39;s functionality. That is to say, by the time “band securing processing” starts, the source device and sink device, for which and to which a band is kept or connected, are determined (for example, the combination of source device  120  and sink device  140 ). Also, in step S 25  and step S 26 , the band the source and sink devices secure and the band to which source and sink devices are connected are decided to be two stream, so that master device  110  secures and connects two bands for the bands for source devices and sink devices. 
         [0096]    In step S 25  and step S 26 , master device  110  checks, with each device, which functionality of two-streams and one-stream that device supports, with reference to source/sink device function management table  200  ( FIG. 4 ), and secures a band to suit that device&#39;s functionality. The details will be described below. 
         [0097]    If at least one of sink devices  140  and  150  is capable of two-stream reception, in step S 25 , master device  110  performs two-stream band securing processing for source devices  120  and  130 , and the step moves to step S 25 . In the two-stream band securing processing, first, master device  110  issues a band securing request (for two bands) to source devices  120  and  130 . In response to this request, source devices  120  and  130  each secure two bands for BD video and audio to output from data output sections  122  and  132  onto channel  100 , by means of communication control section  113 . 
         [0098]    In step S 26 , master device  110  performs processing of connecting the two streams of band of sink devices  140  and  150 , and the step moves onto step S 29 . In the two stream band connecting processing, first, master device  110  issues a band connection request (for two bands/connecting destination band information (information such as the band number of connecting destination source devices), to sink devices  140  and  150 . In response to this request, sink devices  140  and  150  connect with the bands for BD video and audio already kept on channel  100  by source devices  120  and  130 , through communication control section  113 , and acquires BD video and audio information from source devices  120  and  130 . 
         [0099]    As shown with one example of source/sink device function management table  200  in  FIG. 4 , the present embodiment assumes that source device  120  and sink device  140  are BDs that are capable of transmitting and receiving two-stream transmission content. Consequently, in above step S 25 , master device  110  performs two-stream band securing processing for source device  120 , and, in above step S 26 , performs two-stream band connecting processing for sink device  140 . 
         [0100]    On the other hand, when there is no request to transmit two-stream transmission content in above step S 21 , the step moves to step S 27 . Also, if in above step S 23  source devices  120  and  130  are not capable of transmitting two streams, the step moves to step S 27 . If in above step S 24  sink devices  140  and  150  are not capable of receiving two streams, the step also moves to step S 27 . 
         [0101]    In step S 27 , master device  110  performs one-stream band securing processing for source devices  120  and  130 . 
         [0102]    In step S 28 , master device  110  performs one-stream band securing processing for sink devices  140  and  150 . 
         [0103]    In step S 29 , master device  110  updates band management table  300  (see  FIG. 8 ) that manages the state of band kept by each device. 
         [0104]    In step S 30 , master device  110  issues to target source devices  120  and  130  a permit to start transmission. Target source devices  120  and  130  start transmission, and the flow is finished. 
         [0105]      FIG. 8  shows one example of band management table  300 . 
         [0106]    As shown in  FIG. 8 , band management table  300  stores a video stream and audio stream for each device type. Band management table  300  is stored in memory section  112  of master device  110  of  FIG. 3 . 
         [0107]    In  FIG. 8 , the devices on channel  100  are source device  120  (source device &lt;1&gt;), sink device  140  (sink device &lt;1&gt;), source device  130  (source device &lt;2&gt;), and sink device  150  (sink device &lt;2&gt;). For each of these device types, the band connecting destinations and contents of video stream  1 , video stream  2 , audio stream  1  and audio stream  2  are saved. 
         [0108]    For example, for source device  120  (source device &lt;1&gt;) being a BD, the band connecting destination of video stream  1  is sink device  140  (sink device &lt;1&gt;) and its content is content  1  video (A). The band connecting destination of video stream  2  is sink device &lt;1&gt; and its content is content  1  video (B). The band connecting destination of audio stream  1  is sink device &lt;1&gt; and its content is content  1  audio (A). The band connecting destination of audio stream  2  is sink device &lt;1&gt; and its content is content  1  audio (B). 
         [0109]    On the other hand, for source device  140  (sink device &lt;1&gt;) being a BD, the band connecting destination of video stream  1  is sink device  120  (source device &lt;1&gt;) and its content is content  1  video (A). The band connecting destination of video stream  2  is source device &lt;1&gt; and its content is content  1  video (B). The band connecting destination of audio stream  1  is source device &lt;1&gt; and its content is content  1  audio (A). The band connecting destination of audio stream  2  is source device &lt;1&gt; and its content is content  1  audio (B). 
         [0110]    By contrast with these, source device  130  (source device &lt;2&gt;), being a DVD for example, uses only one stream of band. Here, with source device &lt;2&gt;, the band connecting destinations and contents of video stream  1  and audio stream  1  secure no band. Likewise, with sink device  150  (sink device &lt;2&gt;), the band connecting destinations and contents of video stream  1  and audio stream  1  secure no band. 
         [0111]    By executing band securing processing of  FIG. 7 , master device  110  determines the bands for source and sink devices to secure, based on source/sink device function management table  200  (see  FIG. 4 ), and secures channel  100  between the source and sink devices. Then, master device  110  updates band management table  300  (see  FIG. 8 ) saved in memory section  112  (see  FIG. 3 ). 
         [0112]    [Band Change Processing] 
         [0113]      FIG. 9  is a flowchart showing band change processing. This is a detailed flow of the “band change processing” of step S 8  in  FIG. 5 . 
         [0114]    The band change processing of  FIG. 9  is carried out only when two streams of band are kept, and is not carried out when only one stream of band is kept at the time of band securing processing ( FIG. 7 ). 
         [0115]    In step S 31 , master device  110  decides whether or not there is a shortage of transmission band by securing two streams of band. If securing two streams of band does not cause a shortage of transmission band, master device  110  decides that this band change processing does not have to be carried out, and terminates this flow. 
         [0116]    If, on the other hand, securing two streams of band causes a shortage of transmission band, in step S 32 , master device  110  checks the method of using content in sink devices  140  and  150 . The details of this content use method of sink devices  140  and  150  will be described later with reference to  FIG. 10  and  FIG. 11 . 
         [0117]    In step S 33 , master device  110  identifies a shortage of band. That is to say, master device  110  decides whether band is “short for video only,” “short for both video and audio” or “short for audio only.” In the event band is “short for video only” or “short for both video and audio,” the step moves to step S 34 , and, in the event band is “short for audio only,” the step moves to step S 39 . 
         [0118]    In step S 34 , master device  110  identifies the state of video transmission. Video transmission states to be identified include “video (mixed)” or “multiple video,” “video (A),” and “video (B).” A BD can display two HD-size (1920×1080) video data items at the same time, and, by using PinP functionality, can output a different video data item on a screen while another video data item is being played back. Above “video (mixed)” or “multiple video” refers to video using this PinP functionality. 
         [0119]    When “video (mixed)” or “multiple video” is identified, in step S 35 , master device  110  changes the band to video (mixed) transmission one stream, and the step moves to step S 38 . 
         [0120]    When “video (A)” is identified, in step S 36 , master device  110  changes the band to video (A) transmission one stream, and the step moves to step S 38 . 
         [0121]    When “video (B)” is identified, in step S 37 , master device  110  changes the band to video (B) transmission one stream, and the step moves to step S 38 . 
         [0122]    In step S 38 , master device  110  decides whether band is short for both video and audio. 
         [0123]    If band is short for both video and audio, the step moves to step S 39 , and, if band is not short for both video and audio, the step moves to step S 43 . 
         [0124]    A transition to step S 39  is given when band is short for both video and audio, and also when band is “short for audio only.” 
         [0125]    In step S 39 , master device  110  identifies the state of audio transmission. Audio transmission states to be identified include “audio (mixed)” or “multiple audio,” “audio (A),” and “audio (B).” 
         [0126]    When “audio (mixed)” or “multiple audio” is identified, in step S 40 , master device  110  changes the band to audio (mixed) transmission one stream, and the step moves to step S 43 . 
         [0127]    When “audio (A)” is identified, in step S 41 , master device  110  changes the band to audio (A) transmission one stream, and the step moves to step S 43 . 
         [0128]    When “audio (B)” is identified, in step S 42 , master device  110  changes the band to audio (B) transmission one stream, and the step moves to step S 38 . 
         [0129]    In step S 43 , master device  110  updates band management table  300  (see  FIG. 8 ), and finishes the present flow. 
         [0130]      FIG. 10  is a control stream diagram for explaining “content use method” of step S 32  in  FIG. 9 . 
         [0131]    As shown in  FIG. 10 , master device  110  issues a content use request to sink devices  140  and  150  on channel  100  (see S 51 ). Using this content use request, master device  110  checks, with sink devices  140  and  150 , which one of two streams the present BD content uses, or whether the present BD content uses both of the two streams. 
         [0132]    Sink devices  140  and  150  having received the content use request transmit content use responses to master device  110  (see S 52 ). Using these content use requests, sink devices  140  and  150  answer which one of the two streams the present BD content uses or whether the present BD content uses both of the two streams. 
         [0133]    Master device  110  updates content use management table  400  (see  FIG. 11 ) held in memory section  112  (see  FIG. 3 ) of master device  110 , based on the content use responses from sink devices  140  and  150  (see S 53 ). 
         [0134]      FIG. 11  show one example of content use management table  400 . 
         [0135]    As shown in  FIG. 11 , content use management table  400  stores video content and audio content per sink device. Content use management table  400  is stored in memory section  112  of master device  100  in  FIG. 3 . 
         [0136]    In  FIG. 11 , sink device  140  (sink device &lt;1&gt;) uses video content in “video AB (mixed)” and uses audio content in “audio AB (mixed)” and in “audio A (alone).” Sink device  150  (sink device &lt;2&gt;) is not subject to use of two streams of video and audio data contents. 
         [0137]    Master device  110  executes the band change processing of  FIG. 9 . In this band change processing, the method of using content is checked by the control stream of  FIG. 10 , and content use management table  400  of  FIG. 11  is updated. 
         [0138]    When another device starts transmission and there is a shortage of channel band, master device  110  checks the method of using received content with sink devices  140  and  150  (see  FIG. 10 ). Then, master device  110  keeps the result of checking the method of using received content, in content use management table  400  in master device  110  of  FIG. 3 . Master device  110  changes the secured band based on content use management table  400 . 
         [0139]    Upon changing a band having been kept, master device  110  checks the situation of use of content with sink devices  140  and  150 , and performs a band control. 
         [0000]    For example, upon identifying the method of using content, if master device  110  identifies one stream of method of using content, master device  110  maintains that method of one stream, or, if master device  110  identifies two or more methods of using content, master device  110  makes the method transmission “mixed transmission” and makes the band one stream. That is to say, upon changing the band to one stream in the situation where two or more methods of using content are involved, master device  110  performs a control to use mixed transmission. Master device  110  disconnects one of the two streams that is not used, and makes the other remaining stream use mixed transmission. 
         [0140]    The reason to use mixed transmission is as follows. Even when two or more methods of using content need to be changed to one stream, it is preferable not to make a user feel awkward. Furthermore, a BD is capable of outputting a plurality of video and audio data items at the same time, like by PinP. The present embodiment utilizes this mixed output of a BD, and, when the band needs to be changed to one stream, leaves the video and audio a user is then using, by means of mixed output. From the user&#39;s perspective, the content that he is using does not end suddenly but is maintained by switching to mixed output. 
         [0141]      FIG. 12  shows one example of band management table  300 , assuming a case where video and audio are both changed to one stream while two-stream output of video and audio is in progress. As in  FIG. 8 , the devices on channel  100  are source device  120  (source device &lt;1&gt;), sink device  140  (sink device &lt;1&gt;), source device  130  (source device &lt;2&gt;), and sink device  150  (sink device &lt;2&gt;). For each of these device types, the band connecting destinations and contents of video stream  1 , video stream  2 , audio stream  1  and audio stream  2  are saved. 
         [0142]    As described above, when two or more content uses methods are involved, master device  110  changes the transmission method to mixed transmission and makes the band one stream. For example, master device  110  performs a band change according to content use management table  400  of  FIG. 11  so that video and audio both change from two-stream video/audio output to one-stream. 
         [0143]    Now, updating from band management table  300  of  FIG. 8  to band management table  300  of  FIG. 12  will be described using content use management table  400  of  FIG. 11 . 
         [0144]    A case will be described here as an example where there is a shortage of band for both video and audio, in respect to the band kept between source device &lt;1&gt; and sink device &lt;1&gt;. Checking content use management table  400  of  FIG. 11 , master device  110  finds out that sink device &lt;1&gt; is using video content in a “AB mixed” state and using two variations of audio content at the same time, “AB mixed” and “A alone.” 
         [0145]    As for video, only “AB mixed” is used, so that the source device uses “A alone” of video stream  1  for “AB mixed” transmission, and releases the band of the other, video stream  2  free. The sink device disconnects video stream  2 , does not disconnect the band of video stream  1 , and receives “AB mixed” from the source device. By this means, only video stream  1  remains (as “AB content”) among the video streams in band management table  300 , and video stream  2  is in a state where band is not kept. 
         [0146]    As for audio, two variations of “AB mixed” and “A alone” are used at the same time, so that the source device uses “A alone” of audio stream  1  for “AB mixed” transmission, and releases the band of the other, audio stream  2  free. The sink device disconnects audio stream  2 , does not disconnect the band of audio stream  1 , and receives “AB mixed” from the source device. By this means, only audio stream  1  remains (as “AB content”) among the audio streams in band management table  300 , and audio stream  2  is in a state where band is not kept. 
         [0147]    This is executed through the processing of step S 35 , step S 36 , step S 37 , step S 40 , step S 41 , and step S 42 , in the flow of  FIG. 9 . In these steps, processing to release and disconnect band is performed. Consequently, by the time to reach step S 43  of updating band management table  300 , the band is changed to one stream. 
         [0148]    [Band Release Processing] 
         [0149]      FIG. 13  is a flowchart showing band release processing. This is a detailed flow of “band release processing” of step S 6  in  FIG. 5 . 
         [0150]    In step S 61 , master device  110  decides whether or not to release all source and sink devices free. When source and sink devices are all going to be released free, the step moves to step S 62 , or, when source and sink devices are not all going to be released free, the step moves to step S 64 . To release all in this context does not mean releasing or disconnecting all bands of source devices and sink devices connected to the channel, and a stream for processing bands which each source device or sink device secures or connects to, is presumed here. This is, for example, processing between source device &lt;1&gt; and sink device &lt;1&gt;. 
         [0151]    Master device  110  performs all-band disconnecting processing with respect to sink devices  140  and  150  in step S 62 , performs all-band release processing with respect to source devices  120  and  130  in step S 63 , and then the step moves onto step S 70 . In the all-band release processing, the band of one of sink devices  140  and  150 , connected to one of source devices  120  and  130 , is entirely released free and disconnected. 
         [0152]    In step S 64 , master device  110  decides whether or not this is video one-stream band releasing, and the step moves to step S 65  in the event of video one-stream band releasing, or the step moves to step S 67  if this is not video one-stream band releasing. 
         [0153]    Master device  110  performs video one-stream band disconnecting processing with respect to sink devices  140  and  150  in step S 65 , and performs video one-stream band release processing with respect to source devices  120  and  130  in step S 66 , and then the step moves to step S 67 . In this video one-stream band disconnecting processing, one-stream band of one of sink devices  140  and  150 , connected with one of source devices  120  and  130 , is released free and disconnected. 
         [0154]    In step S 67 , master device  110  decides whether or not this is audio one-stream band releasing, and the step moves to step S 68  in the event of audio one-stream band releasing, or the step moves to step S 70  if this is not audio one-stream band releasing. 
         [0155]    Master device  110  performs audio one-stream band disconnecting processing with respect to sink devices  140  and  150  in step S 68 , and performs audio one-stream band release processing with respect to source devices  120  and  130  in step S 69 , and then the step moves to step S 70 . In this audio one-stream band disconnecting processing, one-stream band of one of sink devices  140  and  150 , connected with one of source devices  120  and  130 , is released free and disconnected. 
         [0156]    In step S 70 , master device  110  updates band management table  300  (see  FIG. 8  and  FIG. 12 ) and finishes the flow. 
         [0157]    As described above, with the present embodiment, upon transmitting a plurality of video and audio data items, master device  110  controls video and audio bands, for source and sink devices, with reference to source/sink device function management table  200  and band management table  300 . Also, upon changing a band having been kept, master device  110  checks the state of channel  100  and the situation of use of content with sink devices  140  and  150 , and performs a band control. For example, when outputting two streams of video ad audio data in one stream, master device  110  changes two streams of video and audio data into one composite stream. By this means, master device  110  is able to manage a multimedia device that is capable of outputting a plurality of video and audio data items at the same time, such as a BD. It is also possible to provide video and audio for a multimedia device connected to a channel of a limited frequency band, in an optimal form for user&#39;s use. Application to a multimedia device control system to be used in a vehicle-mounted environment is suitable. 
         [0158]    The above descriptions show an embodiment of the present invention by way of example and by no means limit the scope of the present invention. 
         [0159]    For example, although source devices  120  and  130 , sink devices  140  and  150  and master device  110  are provided separately, it is equally possible to provide master device  110  as part of source devices  120  and  130  or sink devices  140  and  150 , inside these devices. 
         [0160]    Furthermore, although an example has been shown with the present embodiment where video and audio are each provided in two stream, a case is possible as well where only one of video and audio is provided in two streams. Furthermore, when video and audio are provided separately, it is equally possible to secure video and audio in the same band and do this with two streams, in two bands. Furthermore, although an example has been described above where video and audio are each provided in two streams, the present invention is equally applicable to cases where video and audio are both provided in a greater number of streams. 
         [0161]    Furthermore, with the embodiment, in band change processing (see  FIG. 9 ), the method of using content is checked (see  FIG. 10 ) with sink devices and then the transmission band is changed. However, it is equally possible to use a method to make the transmission method mixed transmission and make the band one stream, on a fixed basis, regardless of the state of sink devices. 
         [0162]    Also, with the embodiment, in band change processing (see  FIG. 9 ), the method of using content is checked (see  FIG. 10 ) with sink devices and then the transmission band is changed. However, the sink devices may at the same time issue a request of a method of changing the transmission band to a master device, and, according to this request, the band may be changed to one stream. 
         [0163]    Furthermore, although the term “multimedia device control system” has been used with the present embodiment for ease of explanation, other terms such as “vehicle-mounted communication apparatus” and “transmission system” may be used as well. 
         [0164]    Furthermore, the types, number and connection method of the circuit components to constitute the above multimedia device control apparatus, including the communication control section, memory section and others, are by no means limited to the above-described embodiment. 
         [0165]    Also, the above-described multimedia device control apparatus, source device, sink device and transmission system can be implemented in the form of a program for making this multimedia device control apparatus function. This program may be then stored in a computer-readable recording medium. 
         [0166]    The disclosure of Japanese Patent Application No. 2008-274876, filed on Oct. 24, 2008, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0167]    The multimedia device control apparatus, source device, sink device and transmission system according to the present invention are suitable for use with a multimedia device control apparatus for controlling multimedia devices by managing channel band in a vehicle-mounted environment. Also, the present invention is by no means limited to a vehicle-mounted environment and is equally applicable to any and all apparatuses as long as a master device to control multimedia devices connected to a channel of a limited frequency band is present. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           100  Channel 
           111  Processing section 
           112  Memory section 
           113  Communication control section 
           120 ,  130  Source device 
           121 ,  131 ,  141 ,  151  Processing section 
           122 ,  132  Data output section 
           123 ,  133 ,  143  and  153  Communication control section 
           140 ,  150  Sink device 
           142 ,  152  Data input section 
           200  Source/sink device function management table 
           300  Band management table 
           400  Content use management table