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MPEG digital storage media (DSM) control command
SIGNAL PROCESSING:
IIYNGE ELSEVIER
Signal Processing:
COMMUNICATION
Image Communication 6 (1995) 521-524
MPEG digital storage media (DSM) control command Si Jun Huang Audio/Video
Information
Research Center, Asia Matsushita Electric (S) Pte Ltd. BLK 1022, Hougang Avenue I, #(W3526, Tai Seng Industrial Estate, Singapore I953 Received
11 October
1993
Abstract This paper reports the current standardization activity of the MPEG digital storage media (DSM) control command. The necessity and the scope of the work are discussed first. The basic functions of the DSM control command that have been specified are described. The extension work of DSM control command is introduced. The position of the DSM control command with respect to various layers in a network application environment is illustrated. Finally, possible applications of DSM control command for various MPEG bitstream operations are highlighted and an application system configuration is shown. Keywords:
Digital storage
media; Digital audio and video coding; Computer
1. Introduction
Digital audio and video sources have a huge amount of data compared to their analog formats. For the storage and transmission of such digital audio and video programs, the Moving Picture Expert Group (MPEG) was established in 1988 by ISO/IEC JTCl. Since then, the MPEG has been working on the development of generic coding algorithms for the compression of moving pictures and associated audio to a much lower coded bit rate. The first phase of the project (MPEG-1) has been successfully completed with the publishing of the International Standard ISO/IEC 11172 in May 1993 [l]. The main parts of the second phase of the project (MPEG-2) are scheduled to be promoted to International Standards ISO/IEC 138 18 and ITU-T Recommendation H.262 in November 1994. 0923-5965/95/$9.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO923-5965(94)00035-2
network;
MPEG
bitstream
The coded MPEG bitstream is usually stored in various digital storage media (DSM) such as CDROM, optical disk, magnetic tape and disk, magnetic-optical disk, RAM-disk, etc. Because there are many different kinds of digital storage media and each DSM has its own specific control commands, the user has to know different sets of specific DSM control commands in order to access the MPEG bitstream from different DSM. Furthermore, the DSM could be at local or at remote site. For the latter case, the kind of DSM is usually unknown to the end user. These two factors make it very difficult for an MPEG application to access the MPEG bitstreams on various DSM. One of the solutions to this problem is to design a generic control command set that is independent of the specific DSM used. This set of commands has been referred to as the MPEG DSM Control Command or DSM CC in short in MPEG community.
522
S.J. Huang / Signal Processing:
Image Communication
The DSM CC is solely designed for various MPEG applications to access various DSM without having to know the information about the specific DSM used. A basic set of DSM CC has already been developed and adopted by the MPEG as an informative part of the Systems standard of the MPEG-2 [2] international standard.
2. Scope of the DSM control command The DSM control commands are defined as a specific application protocol to provide the basic functions specific to the MPEG bitstream on digital storage media. It gives provisions for both client and server to conduct such operations as connection, playback, storage, editing, remultiplexing, etc., by the same syntax and semantics. The defined DSM CC is independent of the type of DSM used, whether the DSM is located at a local or remote site, the network transmission protocol with which the DSM CC is interfaced and the operation system on which the DSM is operated. An MPEG bitstream is defined as an MPEG-1 Systems stream, an MPEG-2 Program stream or an MPEG-2 Transport stream. The definition of these streams could be found in [l, 23.
3. Functions of the DSM CC According to the complexity and the application requirements, the functions and operations of the DSM CC could be divided into two parts. The first part is the very basic MPEG bitstream operation control commands with following functions: - Stream selection command This command is used to select a bitstream and specify an operation mode. The DSM will send an acknowledgement to the command issuer to state whether the service selected by this command can be provided by the DSM. - Play command This command is the request to play an identified MPEG bitstream from a given presentation time. The speed and direction of the play can be specified so that various trick modes are supported.
6 (1995) 521-524
Such trick modes include fast forward, fast backward, pause, resume, step and stop. - Store command This command is the request to record an MPEG bitstream to a DSM. Apart from the above basic functions, the second part of the commands listed below has been defined as the extension work of DSM CC [3]. - Multi-user operation The DSM CC will support multi-user connections where more than one user access the same server in the same session. - Reservation mechanism The DSM CC will allow a client to make a reservation with the server for providing a session or a bitstream playback service at a later specified time. _ Server capability information The DSM CC will permit the notification of the server’s capabilities to the end user. The capabilities could include playback, storage, fast forward, fast backward, slow motion, de-multiplex and re-multiplex, etc. - Directory information The DSM CC will provide the information about the directory of a DSM and various attributes of the MPEG bitstreams. Such information may not be available from a conventional application programmer’s interface (API). The directory information may include the following attributes or elements: - bitstream type, _ entry points for random access, - program descriptors, - bitstream IDS, size, bitrates, - date of recording, origination data and copy number, - historical tracking data. - Bitstream edit function The DSM CC will provide commands for various editing operations on MPEG bitstreams. Such edit functions probably includes following: _ create a new multiplexed bitstream from a multiplexed bitstream, _ create a multiplexed bitstream from several nonmultiplexed bitstreams, - insert a section of bitstream into another bitstream, - delete a section of a bitstream.
S.J. Huang J Signal Processing:
Image Communication
6 (1995) 521-524
broadcasting pitals, etc.
5.2. Interactive
523
industry, educational institutes, hos-
video service
This application provides interactive audio and video information to users. Such a service can be used to provide information about tour, hotels, interesting places to visit, etc., to customers. This kind of service could also be used for electronic shopping in which various products are introduced by audio and video.
5.3. Video network
Network
Fig. 1. The position figuration.
of DSM CC protocol
in the network
con-
4. Position of the DSM CC protocol in network configuration Fig. 1 shows how the DSM CC protocol is incorporated into the network with respect to various layers of the network configuration. The DSM CC protocol is above the network transport protocols such as ATM and TCP/IP. This feature determines that the error correction and data transmission issues shall not be covered by the DSM CC protocol. The DSM CC protocol is below the API layer. This feature determines that such issues as login mechanism, security control, account record, etc., shall not be covered by the DSM CC protocol either. The DSM CC is meant purely for the specific operation of the MPEG bitstreams.
5. Possible applications of DSM CC 5. I. Video on demand
This application provides customer demanded or ordered video programs through certain communication channels. The customer could select one of the video programs from a video server. Such an application is required by the hotel industry,
This includes various applications where video data are exchanged through a kind of computer network that can be used to transmit video data. Users could retrieve AV information through the video network to their terminals. Electronic publishing is one example of this kind of applications. Fig. 2 demonstrates a typical configuration for the above mentioned application. A client may request an MPEG bitstream operation from a server by issuing a DSM control command. This command is converted into a bitstream by the DSM CC encoder. The DSM CC bitstream is multiplexed by a systems multiplexer to generate a systems bitstream. The systems bitstream is transmitted by a network transport protocol to the server. The received systems bitstream at the server is demultiplexed by a systems demultiplxer. The output of the system codec, for this case, is a DSM CC bitstream that is then sent to a DSM CC decoder. The decoded DSM CC is sent to the DSM to control its operation. If the DSM control command is a normal play command, the DSM will send the audio and video bitstream to a system multiplexer where they are multiplexed to form a systems bitstream. This systems bitstream is transmitted through the network to the client. It is first demultiplexed by a system demultiplexer to give a video bitstream to a video decoder and the audio bitstream to an audio decoder, where they are decoded to form the reconstructed video and audio signals for presentation. If the DSM CC is a fast forward (FF) or a fast
524
S.J. Huang / Signal Processing:
DSM CCIACK
Image Communication
DSM CCYACK Bitstream
6 (1995) 521-524
ISM CUACK litstream
DSM CC Codec
I
DSM CC/ACK
FF/FR Mode Audio 4 Decoder Audio bitstream
Client
Server
Fig. 2. An MPEG video network configuration with DSM CC.
rewind (FR) operation, it is the responsibility of the DSM to produce a suitable bitstream corresponding to the requested mode. Therefore, the DSM may need to have a special FF/FR video encoder in order to generate the FF/FR bitstream. At the client site, the system demultiplexer will decode an FF/FR mode signal from the systems bitstream and notify the mode to the video decoder for its proper operation in support of the FF/FR bitstream decoding.
know the details of the specific control command of each type of DSM. Many MPEG applications will need to use this set of control commands. This paper briefly introduces the basic concepts of the DSM control commands and suggests some applications and their possible configurations.
References
Cl1 IS 11172, Coding of moving pictures and associated audio 6. Conclusion MPEG DSM control command is a set of generic codes that enables MPEG users to access various DSM at local or remote sites without having to
for digital storage media at up to about 1.5Mbit/s, May 1993. N0701. ISO/IEC 13818-1 VI ISO-IEC/JTCl/SC29/‘WGll (MPEG-2 Systems), March 1994. N0556, Proposal for addic31 ISO-IEC/JTCl/SC29/WGll tional work on DSM control command, DSM Group.
IIYNGE ELSEVIER
Signal Processing:
COMMUNICATION
Image Communication 6 (1995) 521-524
MPEG digital storage media (DSM) control command Si Jun Huang Audio/Video
Information
Research Center, Asia Matsushita Electric (S) Pte Ltd. BLK 1022, Hougang Avenue I, #(W3526, Tai Seng Industrial Estate, Singapore I953 Received
11 October
1993
Abstract This paper reports the current standardization activity of the MPEG digital storage media (DSM) control command. The necessity and the scope of the work are discussed first. The basic functions of the DSM control command that have been specified are described. The extension work of DSM control command is introduced. The position of the DSM control command with respect to various layers in a network application environment is illustrated. Finally, possible applications of DSM control command for various MPEG bitstream operations are highlighted and an application system configuration is shown. Keywords:
Digital storage
media; Digital audio and video coding; Computer
1. Introduction
Digital audio and video sources have a huge amount of data compared to their analog formats. For the storage and transmission of such digital audio and video programs, the Moving Picture Expert Group (MPEG) was established in 1988 by ISO/IEC JTCl. Since then, the MPEG has been working on the development of generic coding algorithms for the compression of moving pictures and associated audio to a much lower coded bit rate. The first phase of the project (MPEG-1) has been successfully completed with the publishing of the International Standard ISO/IEC 11172 in May 1993 [l]. The main parts of the second phase of the project (MPEG-2) are scheduled to be promoted to International Standards ISO/IEC 138 18 and ITU-T Recommendation H.262 in November 1994. 0923-5965/95/$9.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO923-5965(94)00035-2
network;
MPEG
bitstream
The coded MPEG bitstream is usually stored in various digital storage media (DSM) such as CDROM, optical disk, magnetic tape and disk, magnetic-optical disk, RAM-disk, etc. Because there are many different kinds of digital storage media and each DSM has its own specific control commands, the user has to know different sets of specific DSM control commands in order to access the MPEG bitstream from different DSM. Furthermore, the DSM could be at local or at remote site. For the latter case, the kind of DSM is usually unknown to the end user. These two factors make it very difficult for an MPEG application to access the MPEG bitstreams on various DSM. One of the solutions to this problem is to design a generic control command set that is independent of the specific DSM used. This set of commands has been referred to as the MPEG DSM Control Command or DSM CC in short in MPEG community.
522
S.J. Huang / Signal Processing:
Image Communication
The DSM CC is solely designed for various MPEG applications to access various DSM without having to know the information about the specific DSM used. A basic set of DSM CC has already been developed and adopted by the MPEG as an informative part of the Systems standard of the MPEG-2 [2] international standard.
2. Scope of the DSM control command The DSM control commands are defined as a specific application protocol to provide the basic functions specific to the MPEG bitstream on digital storage media. It gives provisions for both client and server to conduct such operations as connection, playback, storage, editing, remultiplexing, etc., by the same syntax and semantics. The defined DSM CC is independent of the type of DSM used, whether the DSM is located at a local or remote site, the network transmission protocol with which the DSM CC is interfaced and the operation system on which the DSM is operated. An MPEG bitstream is defined as an MPEG-1 Systems stream, an MPEG-2 Program stream or an MPEG-2 Transport stream. The definition of these streams could be found in [l, 23.
3. Functions of the DSM CC According to the complexity and the application requirements, the functions and operations of the DSM CC could be divided into two parts. The first part is the very basic MPEG bitstream operation control commands with following functions: - Stream selection command This command is used to select a bitstream and specify an operation mode. The DSM will send an acknowledgement to the command issuer to state whether the service selected by this command can be provided by the DSM. - Play command This command is the request to play an identified MPEG bitstream from a given presentation time. The speed and direction of the play can be specified so that various trick modes are supported.
6 (1995) 521-524
Such trick modes include fast forward, fast backward, pause, resume, step and stop. - Store command This command is the request to record an MPEG bitstream to a DSM. Apart from the above basic functions, the second part of the commands listed below has been defined as the extension work of DSM CC [3]. - Multi-user operation The DSM CC will support multi-user connections where more than one user access the same server in the same session. - Reservation mechanism The DSM CC will allow a client to make a reservation with the server for providing a session or a bitstream playback service at a later specified time. _ Server capability information The DSM CC will permit the notification of the server’s capabilities to the end user. The capabilities could include playback, storage, fast forward, fast backward, slow motion, de-multiplex and re-multiplex, etc. - Directory information The DSM CC will provide the information about the directory of a DSM and various attributes of the MPEG bitstreams. Such information may not be available from a conventional application programmer’s interface (API). The directory information may include the following attributes or elements: - bitstream type, _ entry points for random access, - program descriptors, - bitstream IDS, size, bitrates, - date of recording, origination data and copy number, - historical tracking data. - Bitstream edit function The DSM CC will provide commands for various editing operations on MPEG bitstreams. Such edit functions probably includes following: _ create a new multiplexed bitstream from a multiplexed bitstream, _ create a multiplexed bitstream from several nonmultiplexed bitstreams, - insert a section of bitstream into another bitstream, - delete a section of a bitstream.
S.J. Huang J Signal Processing:
Image Communication
6 (1995) 521-524
broadcasting pitals, etc.
5.2. Interactive
523
industry, educational institutes, hos-
video service
This application provides interactive audio and video information to users. Such a service can be used to provide information about tour, hotels, interesting places to visit, etc., to customers. This kind of service could also be used for electronic shopping in which various products are introduced by audio and video.
5.3. Video network
Network
Fig. 1. The position figuration.
of DSM CC protocol
in the network
con-
4. Position of the DSM CC protocol in network configuration Fig. 1 shows how the DSM CC protocol is incorporated into the network with respect to various layers of the network configuration. The DSM CC protocol is above the network transport protocols such as ATM and TCP/IP. This feature determines that the error correction and data transmission issues shall not be covered by the DSM CC protocol. The DSM CC protocol is below the API layer. This feature determines that such issues as login mechanism, security control, account record, etc., shall not be covered by the DSM CC protocol either. The DSM CC is meant purely for the specific operation of the MPEG bitstreams.
5. Possible applications of DSM CC 5. I. Video on demand
This application provides customer demanded or ordered video programs through certain communication channels. The customer could select one of the video programs from a video server. Such an application is required by the hotel industry,
This includes various applications where video data are exchanged through a kind of computer network that can be used to transmit video data. Users could retrieve AV information through the video network to their terminals. Electronic publishing is one example of this kind of applications. Fig. 2 demonstrates a typical configuration for the above mentioned application. A client may request an MPEG bitstream operation from a server by issuing a DSM control command. This command is converted into a bitstream by the DSM CC encoder. The DSM CC bitstream is multiplexed by a systems multiplexer to generate a systems bitstream. The systems bitstream is transmitted by a network transport protocol to the server. The received systems bitstream at the server is demultiplexed by a systems demultiplxer. The output of the system codec, for this case, is a DSM CC bitstream that is then sent to a DSM CC decoder. The decoded DSM CC is sent to the DSM to control its operation. If the DSM control command is a normal play command, the DSM will send the audio and video bitstream to a system multiplexer where they are multiplexed to form a systems bitstream. This systems bitstream is transmitted through the network to the client. It is first demultiplexed by a system demultiplexer to give a video bitstream to a video decoder and the audio bitstream to an audio decoder, where they are decoded to form the reconstructed video and audio signals for presentation. If the DSM CC is a fast forward (FF) or a fast
524
S.J. Huang / Signal Processing:
DSM CCIACK
Image Communication
DSM CCYACK Bitstream
6 (1995) 521-524
ISM CUACK litstream
DSM CC Codec
I
DSM CC/ACK
FF/FR Mode Audio 4 Decoder Audio bitstream
Client
Server
Fig. 2. An MPEG video network configuration with DSM CC.
rewind (FR) operation, it is the responsibility of the DSM to produce a suitable bitstream corresponding to the requested mode. Therefore, the DSM may need to have a special FF/FR video encoder in order to generate the FF/FR bitstream. At the client site, the system demultiplexer will decode an FF/FR mode signal from the systems bitstream and notify the mode to the video decoder for its proper operation in support of the FF/FR bitstream decoding.
know the details of the specific control command of each type of DSM. Many MPEG applications will need to use this set of control commands. This paper briefly introduces the basic concepts of the DSM control commands and suggests some applications and their possible configurations.
References
Cl1 IS 11172, Coding of moving pictures and associated audio 6. Conclusion MPEG DSM control command is a set of generic codes that enables MPEG users to access various DSM at local or remote sites without having to
for digital storage media at up to about 1.5Mbit/s, May 1993. N0701. ISO/IEC 13818-1 VI ISO-IEC/JTCl/SC29/‘WGll (MPEG-2 Systems), March 1994. N0556, Proposal for addic31 ISO-IEC/JTCl/SC29/WGll tional work on DSM control command, DSM Group.