Abstract:
In a video processing method, plural pieces of digital data such as video and audio data are inputted together with an instruction signal indicating whether the plural pieces of digital data are to be multiplexed or not, and the plural pieces of digital data are multiplexed when the instruction signal instructs to multiplex the digital data, and then the multiplexed digital data are outputted together with a flag indicating whether the digital data are multiplexed or not. Therefore, when video and audio data are not multiplexed or when there is a scene description for handling plural pieces of video data, the video and audio data can be recorded or transmitted in like manner as multiplexed data.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a method and an apparatus for video processing, which are used for recording digital data such as video and audio data on a disk, a memory, or the like, and reproducing recorded digital data.  
         BACKGROUND OF THE INVENTION  
         [0002]    With recent development in video and audio digitization, there has been promoted standardization of recording and playback of compressed video and audio data in/from storage media. A DVD is one of these standards. Although a DVD has conventionally been used for playback only, as a recordable DVD has recently been put to practical use, a video recording standard for recording video and audio data is established.  
           [0003]    Hereinafter, a description will be given of a video recording standard that is discussed in “Transactions of the Institute of Image Information and Television Engineers, Vol.53, No.10, “Trends in Standardization of Optical Disk”, Murase et al.”, as an example of a conventional video processing method for video recording and playback, with reference to the drawings.  
           [0004]    FIGS.  7 ( a )- 7 ( d ) are diagrams for explaining a video recording standard as an example of conventional video recording/playback standard. FIG. 7( a ) is a block diagram of a recording/playback apparatus, and FIGS.  7 ( b )- 7 ( d ) are diagrams for explaining a recorded video and audio format. In FIG. 7( a ), reference numeral  71  denotes a codec unit for compressing video and audio data and multiplexing the compressed video and audio data, or demultiplexing the compressed and multiplexed video and audio data and decompressing the video and audio data, and reference numeral  72  denotes a drive for recording the data generated in the codec unit  71  on a recording medium, or playing the data from the recording medium.  
           [0005]    Hereinafter, the operation of the recording/playback apparatus will be described with reference to FIGS.  7 ( a )- 7 ( d ) Digitized video and audio data are supplied from the outside to a video codec  711  and an audio codec  712 , respectively, and compressed. The compressed data are inputted to a multipiexer/demultiplexer  713 . The data recorded by a DVD are constituted in units of Video Objects as shown in FIG. 7( b ), and each Video Object corresponds to a program. Each Video Object is composed of plural video Object Units as shown in FIG. 7( c ), and each Video Object Unit is, for example, a random-accessible unit. Each Video Object Unit is further divided into Video Packs and Audio Packs as shown in FIG. 7( d ). A Pack is a unit of actual disk recording and playback, such as 2048 bytes.  
           [0006]    The multiplexer/demultiplexer  713  receives the inputted compressed video and audio data and divides them into Packs, assigns time information for synchronous reproduction to each Pack, and then, multiplexes Video Packs and Audio Packs as shown in FIG. 7( d ) to output the result to the track buffer  714 . Further, the data outputted from the track buffer  714  in the codec  71  are assigned with data for error correction by the error correction unit  721  in the drive  72 , modulated by the modulator  722 , and then recorded into the DVD-RAM disk  724 . On the other hand, the data recorded therein are demodulated and error corrected according to the procedure reverse to that of the recording, and inputted to the multiplexer/demultiplexer  713  through the track buffer  714 . Because the inputted data are multiplexed so as to have a format of FIGS.  7 ( d )- 7 ( d ), data is demultiplexed with distinguishing between video and audio referring to the headers, and the demultiplexed video and audio data are inputted to the video codec  711  and the audio codec  712 , respectively, to be decompressed and played back.  
           [0007]    In the conventional video processing apparatus constructed as described above, the compressed and multiplexed data, which are recorded so as to have a predetermined format, are demultiplexed into video data and audio data and they are played back, thereby performing data recording/playback complying with the video recording standard. However, the construction shown in FIG. 7( a ) which operates so as to have formats as shown in FIG. 7( b )- 7 ( d ) has following two drawbacks.  
           [0008]    Firstly, the formats of data which are to be recorded onto a DVD necessarily carries out multiplexing of video and audio as shown in FIG. 7( d ). However, carrying out multiplexing of video and audio would be a large load when high-speed data processing is required. In recent years, with reduction in costs of semiconductor memories, medium that can perform high-speed data inputting and outputting differently from DVD, has been recognized as storage medium. When using medium such as semiconductor memories performing high-speed data inputting and outputting, the processing which have been carried out in case of employing a DVD, i.e., multiplexing video data and audio data and alternately recording those on tracks, and reading them by tracing the tracks with a pick-up at a fixed rate, are not required and, moreover, data recorded at an arbitrary position on the medium can be taken by employing random access accessing. Thus, data are not necessarily required to be multiplexed, and video and audio data can be apparently simultaneously inputted or outputted. Among multimedia data transmitted through the Internet, we can find many of them performing no multiplexing of video and audio data. In view of this, multiplexing and demultiplexing at recording are nothing but applying load to equipment.  
           [0009]    Secondly, in MPEG4 (the standard for compression of moving pictures established by ISO/IEC on 1999), a plurality of video and audio data can be handled in one program. Then, which video or which audio data are to be played at which position and at which time are expressed by data called “scene description”. In this case, the data to be played are determined by the content of the scene description, and therefore, it was impossible to multiplex plural pieces of video and audio data at predetermined intervals as in the conventional video processing.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is made to solve the above-described problems and has for its object to provide a method and an apparatus for video processing, that can record or transmit video and audio data without multiplexing, as required.  
           [0011]    Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the scope of the invention will be apparent to those of skill in the art from the detailed description.  
           [0012]    According to a first aspect of the present invention, a video processing method comprises: receiving plural pieces of digital data such as video and audio data, and an instruction signal indicating whether the plural pieces of digital data are to be multiplexed or not; multiplexing the plural pieces of digital data when the instruction signal indicates the digital data to be multiplexed; and outputting the multiplexed digital data, and a flag indicating whether the digital data are multiplexed or not. Since whether the video and audio data are multiplexed or not can be discriminated by the flag, video and audio data are not necessarily multiplexed at recording, whereby recording and playback of video and audio data can be performed separately. Therefore, the load to equipment by multiplexing and demultiplexing at recording can be reduced.  
           [0013]    According to a second aspect of the present invention, a video processing method comprises: receiving plural pieces of digital data such ad video and audio data, and scene description data indicating the playback times or playback positions of the respective digital data; setting a scene description flag indicating whether there is present a scene description or not; and outputting the digital data and the scene description flag. In this method, whether there is a scene description or not is discriminated by the flag, and when there is a scene description, data recording/playback is performed with reference to the scene description. Therefore, even when plural pieces of video and audio data are included in a program as in MPEG4 data, the load to equipment by multiplexing and demultiplexing can be reduced.  
           [0014]    According to a third aspect of the present invention, the video processing method of the first aspect further comprises: generating access information for making an access to the digital data at an arbitrary time and at an arbitrary position; and outputting the digital data accessed and the access information. Therefore, it is easy to make access to arbitrary data of video and audio data which are compressed by such as MPEG coding.  
           [0015]    According to a fourth aspect of the present invention, the video processing method of the second aspect further comprises: generating access information for making an access to the digital data at an arbitrary time and at an arbitrary position; and outputting the digital data accessed and the access information. Therefore, it is easy to make access to arbitrary data of video and audio data which are compressed by such as MPEG coding.  
           [0016]    According to a fifth aspect of the present invention, a video processing apparatus comprises: audio coding means for coding audio data; video coding means for coding video data; and multiplexing means for receiving plural pieces of digital data coded, and an instruction signal indicating whether the plural pieces of digital data are to be multiplexed or not, and multiplexing the plural pieces of digital data when the instruction signal indicates the digital data to be multiplexed, and outputting the multiplexed digital data and a flag indicating whether the digital data are multiplexed or not. Since whether video and audio data are multiplexed or not can be discriminated by the flag, video and audio data are not necessarily multiplexed at recording, whereby recording and playback of video and audio data can be performed separately. Therefore, the load to equipment by multiplexing and demultiplexing at recording can be reduced.  
           [0017]    According to a sixth aspect of the present invention, a video processing method comprises: receiving plural pieces of digital data such as video and audio data, and a flag indicating whether the plural pieces of digital data are multiplexed or not; demultiplexing the plural pieces of digital data when the flag indicates that the digital data are multiplexed; and outputting the demultiplexed digital data, respectively. Therefore, it is possible to easily read and play data from a single recording medium in which both of multiplexed digital data and not-multiplexed digital data are included.  
           [0018]    According to a seventh aspect of the present invention, a video processing method comprises: receiving plural pieces of digital data such as video and audio data, and a scene description flag indicating whether there is scene description data that indicate the playback times or playback positions of the respective digital data; and outputting the digital data and he scene description data when the scene description flag indicates that there is scene description data. Therefore, even when plural pieces of video and audio are included in a program as in MPEG4 data, the load to equipment by multiplexing and demultiplexing can be reduced.  
           [0019]    According to an eighth aspect of the present invention, a video processing apparatus comprises: audio decoding means for decoding digitized audio data; video decoding means for decoding digitized video data; and demultiplexing/control means for detecting a flag indicating whether the plural pieces of digital data are multiplexed or not, demultiplexing the plural pieces of digital data when the flag indicates that the digital data are multiplexed, and controlling the audio decoding means and the video decoding means so as to output the plural pieces of digital data separately. Therefore, it is possible to easily read and play data from a single recording medium in which both of multiplexed digital data and not-multiplexed digital data are included.  
           [0020]    According to a ninth aspect of the present invention, a video processing apparatus comprises: audio coding means for coding audio data; video coding means for coding video data; multiplexing means for receiving the plural pieces of digital data coded, and an instruction signal indicating whether the plural pieces of digital data are to be multiplexed or not, and multiplexing the plural pieces of digital data when the instruction signal indicates the digital data to be multiplexed, and outputting the multiplexed digital data and a flag indicating whether the digital data are multiplexed or not; and data recording means for recording the multiplexed digital data and the flag indicating whether the digital data are multiplexed or not onto the same recording medium. Since whether video and audio data are multiplexed or not can be discriminated by the flag, video and audio data are not necessarily multiplexed at recording and, therefore, it is possible to create a recording medium in which multiplexed digital data and non-multiplexed digital data are included.  
           [0021]    According to a tenth aspect of the present invention, there is provided a data recording medium containing a video processing program for making a computer execute a process of recording plural pieces of digital data such as video and audio data onto the same recording medium, and the video processing program comprises: receiving plural pieces of digital data such as video and audio data, and an instruction signal indicating whether the plural pieces of digital data are to be multiplexed or not; multiplexing the plural pieces of digital data when the instruction signal indicates the digital data to be multiplexed; outputting the multiplexed digital data, and a flag indicating whether the digital data are multiplexed or not; and recording the outputted multiplexed digital data and the flag indicating whether the digital data are multiplexed or not onto the same recording medium. Therefore, it is possible to realize, by software, a video processing method that can reduce the load to equipment by multiplexing and demultiplexing at recording.  
           [0022]    According to an eleventh aspect of the present invention, there is provided a data recording medium containing a video processing program for making a computer execute a process of recording plural pieces of digital data such as video and audio data onto the same recording medium, and the video processing program comprises: reading plural pieces of digital data such as video and audio data, and a flag indicating whether the plural pieces of digital data are multiplexed or not; judging whether the plural pieces of digital data are multiplexed or not, on the basis of the flag; and demultiplexing the plural pieces of digital data when it is judged that the plural pieces of digital data are multiplexed, and separately outputting the respective digital data obtained. Therefore, it is possible to realize, by software, a video processing method for reading and playing data from a single recording medium in which multiplexed digital data and non-multiplexed digital data are included.  
           [0023]    According to a twelfth aspect of the present invention, there is provided a data recording medium containing plural pieces of digital data such as video and audio data, and multiplexing flags corresponding to the respective digital data and indicating whether the respective digital data are multiplexed or not. Therefore, it is possible to realize a recording medium that can reduce the load to equipment when multiplexed data is demultiplexed.  
           [0024]    According to a thirteenth aspect of the present invention, there is provided a data structure for recording coded video and audio signals that are obtained by coding digital video and audio signals, and the data structure comprises plural pieces of digital data such as video and audio data, and multiplexing flags indicating whether the respective digital data are multiplexed or not. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a block diagram illustrating the construction of a video processing apparatus according to an embodiment of the present invention.  
         [0026]    [0026]FIG. 2 is a diagram for explaining a recording format on a recording medium that is processed by the video processing apparatus shown in FIG. 1.  
         [0027]    FIGS.  3 ( a ) and  3 ( b ) are diagrams for explaining the contents of management information of the recording format shown in FIG. 2.  
         [0028]    [0028]FIG. 4 is a flowchart for explaining the operation of a CPU at recording, which CPU is one of components of the video processing apparatus shown in FIG. 1.  
         [0029]    [0029]FIG. 5 is a flowchart for explaining the operation of the CPU at playback.  
         [0030]    [0030]FIG. 6 is a diagram for explaining a recording medium, in which a program and data for implementing the video processing apparatus with a computer are recorded, and a computer system.  
         [0031]    FIGS.  7 ( a )- 7 ( d ) are diagrams for explaining a video recording standard as an example of a conventional video recording/playback standard. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    Hereinafter, a video processing method and a video processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.  
         [0033]    [0033]FIG. 1 is a block diagram illustrating a video processing apparatus according to the embodiment of the invention. In FIG. 1, reference numeral  11  denotes a multiplexing control unit as a multiplexing means for multiplexing plural pieces of digital data such as video and audio, and demultiplexing the multiplexed data into the respective data, and this multiplexing control unit  11  is implemented by a CPU. Reference numeral  12  denotes a recording/playback unit for performing recording and playback,  13  denotes a recording medium,  14  denotes an audio codec as audio coding (decoding) means,  15  denotes a video codec as a video coding (decoding) means, and  16  denotes a network interface. Further, reference numeral  17  denotes a flag indicating whether data is multiplexed or not, and this flag  17  is inputted from the outside by the user. FIGS. 2 and 3 are diagrams for explaining a recording format according to the embodiment of the invention, FIG. 4 is a flowchart illustrating the operation of the CPU  11  at recording, and FIG. 5 is a flowchart illustrating the operation of the CPU  11  at playback.  
         [0034]    Hereinafter, a video recording/playback method, as video processing, will be described with reference to FIGS.  1  to  5 , taking the video processing apparatus shown in FIG. 1 as an example.  
         [0035]    [0035]FIG. 2 shows a data format on a recording medium. With reference to FIG. 2, video and audio data are managed in units of programs, and a plurality of programs can be recorded on a single recording medium. Besides the programs, information for managing the whole of the programs in the recording medium is recorded on the recording medium. Each program is composed of data having a predetermined size, which is called an object. In the case of shooting with a video camera, an object corresponds to video or audio that is shot from when the shooting is started to when the shooting is ended, and a program corresponds to video or audio that is shot from when the video camera is powered on to when the video camera is powered off. Of course, one program may be composed of one object, and only one program may be recorded on one recording medium. In FIG. 2, three programs #1, #2, and #3 are recorded on one recording medium. In tho program #1, video and audio objects are multiplexed (AV objects). In the program #2, video and audio objects are not multiplexed, i.e., video objects and audio objects are recorded as separated objects. In the program #3, it is uncertain whether video and audio objects are multiplexed or not, and scene description data is recorded in addition to the video and audio data. Further, in FIG. 2, access information used for random access is recorded in addition to the video and audio data.  
         [0036]    [0036]FIG. 3( a ) shows an example of contents of management information shown in FIG. 2. The management information is divided into program units, and each program has management information for each object. An object ID is a number to identify an object, and one object ID is associated with each object recorded. Each program has a scene description flag, and each object has a multiplexing flag. The scene description flag indicates whether the program is managed by a scene description or not, and when this flag is “1”, scene description data surely exists in this program. The multiplexing flag indicates whether video and audio are multiplexed or not in each object recorded. In the example of FIG. 3, since the scene description flag is “0” in the program #1, no scene description exists in this program. Since the multiplexing flag corresponding to each object is “1”, video and audio data are multiplexed.  
         [0037]    Further, since the multiplexing flags are “0” in the program #2, video and audio data are separately recorded in this program. In the program #1, there is only one AV object ID even though video and audio data are not multiplexed. The reason is as follows. Since video and audio data can be distinguished from each other by extensions of files or the like, video and audio data can be managed with one AV object ID, whereby the amount of data of the management information can be reduced of course, the method of describing AV object ID is not restricted thereto, and plural pieces of AV object ID corresponding to data required for synchronous reproduction may he listed in the management information.  
         [0038]    In the program #3, since the scene description flag is “1”, a scene description ID follows the scene description flag. An example of scene description is shown in FIG. 3( b ). As shown in FIG. 3( b ), the scene description describes when (time) and where (position) the corresponding data should be played. Accordingly, data to be played can be determined with reference to the scene description. Further, although, in the management information, the number of objects constituting each program is recorded, the number of objects is zero when there is a scene description. The reason is as follows. Since all objects are managed by the scene description, only the scene description is altered even when the number of objects is changed by editing or the like, whereby the load of editing the whole management information is reduced.  
         [0039]    Next, a method for recording data in the format shown in FIGS. 2 and 3 will be described with reference to FIGS. 1 and 4. In FIG. 1, the audio codec  14  and the video codec  15  compress inputted video and audio data, respectively, like the conventional ones. When the compressed data are inputted to the CPU  11  (step S 411 ), the CPU  11  checks whether a scene description is inputted or not (step S 412 ). When there is no scene description, the CPU  11  sets the scene description flag at 0 (S 414 ), and generates access information for random access (step S 415 ). The information for random access is, in the case of MPEG video compression, the number of data, the number of frames, or the time up to an intra-frame coded frame. In the case of audio data, it is the audio frame number corresponding to the access point of video, or the number of frames up to the audio frame. However, the information for random access is not restricted to those mentioned above, and any information (amount of data, numeric value, etc.) serving as an index of access may be used. Then, the process proceeds to step S 416 , wherein recording of access point data is carried out.  
         [0040]    Next, in step S 417 , it is judged whether the video and audio data are to be multiplexed at recording or not. When the program #1 indicates AV-multiplexed recording (refer to step S 418 ), the compressed video and audio data are divided into packets of a predetermined length (step S 419 ), and information such as synchronous reproduction or the like is assigned to the video and audio data for every predetermined length packets (step S 420 ). Next, the video and audio packets are multiplexed and transmitted to the recording/playback unit  12  (step S 421 ), and recorded an the recording medium  13  together with the management information and the access information (step S 423 ). The processes of steps S 415  to S 423  are repeated until the end of data is detected in step S 424 . When the end of data is detected, the management information is updated (step S 432 ) to conclude the data processing.  
         [0041]    On the other hand, when there is no scene description data and it is judged in step S 417  that AV multiplexing should not be performed, the multiplexing flag is set at 0 (step S 428 ), and the video and audio data are assigned with information for synchronization and then transmitted to the recording/playback unit  12 . When there is scene description data, the name of reference data in the scene description data is rewritten so that the name of the video and audio data written in the scene description data coincides with the name of the data to be recorded (step S 426 ) Thereafter, access information is generated (step S 429 ), the data are assigned with information for synchronization, and then transmitted to the recording/playback unit  12 . Further, with respect to the management information shown in FIG. 3( a ), the CPU  11  generates a scene description flag and a multiplexing flag corresponding to each program and each object simultaneously with data processing, and records these flags in the field of management information, together with the number of objects, the object ID, and the like (step S 432 ). By the operation mentioned above, the video and audio data having the format shown in FIGS. 2 and 3 are recorded.  
         [0042]    Next, a method for playing the data recorded with the format shown in FIGS. 2 and 3 will be described with reference to FIGS. 1 and 5. Since, in the format shown in FIG. 2, it is premised that playback is carried out in units of programs, the procedure for playing one program will be described hereinafter.  
         [0043]    Initially, in step S 511 , the management information of the program is read. Then, it is judged whether there exists a scene description or not, by the scene description flag in the management information (step S 512 ).  
         [0044]    When there is no scene description, the data are inputted in step S 513 , and it is judged whether the data are multiplexed or not by the multiplexing flag (step S 514 ). When it is judged that the data are multiplexed, the multiplexed data are demultiplexed into video data and audio data (step S 515 ), and the respective data are transmitted to the corresponding codecs (step S 516 ) to be played synchronously according to the information for synchronization attached to the headers. Thereafter, the processes of steps S 513  to S 516  are repeated until the end of data is detected in step S 517 . On the other hand, when it is judged in step S 514  that the video data and the audio are not multiplexed, step S 515  is bypassed, and the respective data are transmitted to the corresponding codecs together with the information for synchronization (step S 516 ).  
         [0045]    On the other hand, when it is judged in step S 512  that there is a scene description, the scene description is reproduced in step S 518 , and the playback times of the respective data and the data to be played are specified from the scene description (step S 519 ). When it is judged in step S 520  that the time to play the data has come, the data is inputted in step S 512 , and the data is played in step S 522 . However, since whether the video data and the audio data are multiplexed or not is usually judged by the information of the scene description, demultiplexing is performed when the video and audio data are multiplexed. When the video and audio data are not multiplexed, the respective data are transmitted to the corresponding codecs together with the information for synchronization. It does not matter whether the video data and the audio data described in the scene description are multiplexed or not. When the video data and the audio data are not multiplexed, the respective data are separately transmitted to the video and audio codecs. Since the order of data to be played is also specified in the scene description, the recorded video and audio data are played according to the order. Thereafter, the processes of steps S 520  to S 522  are repeated until the end of data is detected in step S 523 . Through the procedure mentioned above, the recorded video and audio can be played whether they are multiplexed or not and, moreover, the recorded video and audio can be played also when there is a scene description.  
         [0046]    [0046]FIG. 6 is a diagram illustrating a recording medium  61  on which a program and data for making a computer execute the video processing according to the present invention are recorded, and a computer system  62 . A semiconductor memory card is assumed as the recording medium  61 . It is possible to make the computer system  62  execute the procedures shown in FIGS. 4 and 5 by programming the procedures and storing the resulted program in the recording medium  61 . Further, the same effects as those described for the embodiments of the invention are achieved by writing the data itself in the recording medium  61 , and playing that data.  
         [0047]    While in the above description a semiconductor memory is used as the data recording medium  61 , other media may be used, for example, a disk like a floppy disk, a CD, or a DVD, or a medium provided with a recording element, like an IC card.  
         [0048]    Further, while in the embodiment of the invention, file management is explained in units of program and objects, the present invention is not restricted thereto, and video and audio may be recorded as they are, without being divided into units of programs.  
         [0049]    Further, while in the embodiment of the invention each program is associated with a scene description flag, the present invention is not restricted thereto, and each object may be associated with a scene description flag. In this case, a scene description object corresponding to each object exists in association with the flag. Further, in the above description, whether video and audio data are to be multiplexed or not is judged for each program. In this case, a multiplexing flag may be assigned not to each object but to each program. Conversely, when a multiplexing flag is assigned to each object, it is possible to mix multiplexed data and non-multiplexed data for each object in the same program.  
         [0050]    Furthermore, while in the embodiment of the invention one piece of video data and one piece of audio data are multiplexed, it is also possible to extend the invention so that plural pieces of video data and plural pieces of audio data are multiplexed.  
         [0051]    Furthermore, while in the embodiment of the invention video processing is described for the case of recording and playing data on/from a recording medium, the present invention is not restricted thereto. For example, in FIG. 1, the recording/playback unit  12  may be replaced with a transmission line interface, and the video processing apparatus may be placed in the middle of the transmission line to perform multiplexing/demultiplexing of transmitted data, addition of flags, and the like. Furthermore, although video and audio data are described with respect to only input and output to/from the codecs, a network interface  16  may be added to the structure of FIG. 1 so that video and audio data can be transmitted to or received by the network.  
         [0052]    Furthermore, while in the embodiment of the invention the CPU  11  performs multiplexing/demultiplexing of video and audio data, addition of multiplexing flags and scene description flags, and judgement of the contents, the present invention is not restricted thereto. The multiplexing/demultiplexing unit may be constituted by hardware, or the respective components may be implemented by different CPUs. Thus, the hardware construction is not limited on a condition that the same operation as described above is achieved.