DSM CC
Encyclopedia
Digital storage media command and control (DSM-CC) is a toolkit for developing control channels associated with MPEG-1
and MPEG-2
streams. It is defined in part 6 of the MPEG-2 standard (Extensions for DSM-CC) and uses a client/server model connected via an underlying network (carried via the MPEG-2 multiplex
or independently if needed).
DSM-CC may be used for controlling the video reception, providing features normally found on Video Cassette Recorders (VCR) (fast-forward, rewind, pause, etc). It may also be used for a wide variety of other purposes including packet data transport. It is defined by a series of weighty standards, principally MPEG-2 ISO
/IEC
13818-6 (part 6 of the MPEG-2 standard).
DSM-CC may work in conjunction with next generation packet networks, working alongside such internet protocols as RSVP
, RTSP, RTP
and SCP
. Although DSM-CC is usually associated with video delivery (via satellite
or terrestrially) and with interactive content, it is also used among audio servers and clients. The architecture describes three main parts of the system: the client
, the server
, and the session resource manager (SRM). The server provides content and other services to the client, and both are "clients" of the SRM. The SRM allocates and manages network resources (such as channels
, bandwidth
, and network address
es.) By combining server and client components together onto the same platforms, peer-to-peer
content access and delivery systems can be constructed.
These specifications include numerous implementation options. For example, MPEG-2 video can be encoded in different ways, and a DSM-CC system can be constructed to include or exclude certain features and interfaces. Normally, an outside specification will define a profile of specific options, allowing systems built using common profiles to interoperate.
DSM-CC defines or extends five distinct protocols:
User-User: Allows remote access by the client to objects on the server. The User-User specification goes beyond the definition of specific server object classes to define classes local to the client, as well as some of the interaction with other parts of the system. The distributed object model is based on CORBA
. Objects are accessed using the internet inter-ORB protocol (IIOP), with some optional extensions. Two subsets, "core" and "extended", are defined. In the model, some clients may also load content onto the server.
User-Network: There are two parts to this protocol: Session and Resource. This protocol is used between the client and SRM, and between the server and SRM. The U-N Session protocol is used to establish sessions with the network, associated with resources with are allocated and released using the U-N Resource protocol.
MPEG transport profiles: The specification provides profiles to the standard MPEG transport protocol (defined by ISO/IEC 13818-1) to allow transmission of event, synchronization, download, and other information in the MPEG transport stream.
Download: Several variations of this protocol allow transfer of content from server to client, either within the MPEG transport stream or on a separate (presumably high-speed) channel. Flow-controlled download allows the download operations to be negotiated and controlled by the client. A variation of download is an autonomous "data carousel" on the server which repeatedly downloads information; the download carousel client waits for the information without initiating the transfer. An extension to the data carousel is the "object carousel", which presents downloaded information as objects compatible with the objects defined by the User-User API. (The choice of download or IIOP protocols is embedded in the object's IOR, so the means of access is transparent to the client application.)
Switched Digital Broadcast-Channel Change Protocol (SDB/CCP): Enables a client to remotely switch from channel to channel in a broadcast
environment. Used to attach a client to a continuous-feed session (CFS) or other broadcast feed. Sometimes used in pay-per-view
.
An implementation does not always need all of these protocols. Almost all implementations in the real world use a subset.
(DMIF) expands upon the MPEG-2 DSM-CC standard (ISO/IEC 13818-6:1998) to enable the convergence of interactive, broadcast and conversational multimedia into one specification which will be applicable to set tops, desktops and mobile stations. The DSM-CC work was extended as part of the ISO/IEC 14496-6 (MPEG-4
Part 6), with the DSM-CC Multimedia Integration Framework (DMIF).
MPEG-1
MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting possible.Today, MPEG-1 has become...
and MPEG-2
MPEG-2
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
streams. It is defined in part 6 of the MPEG-2 standard (Extensions for DSM-CC) and uses a client/server model connected via an underlying network (carried via the MPEG-2 multiplex
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
or independently if needed).
DSM-CC may be used for controlling the video reception, providing features normally found on Video Cassette Recorders (VCR) (fast-forward, rewind, pause, etc). It may also be used for a wide variety of other purposes including packet data transport. It is defined by a series of weighty standards, principally MPEG-2 ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
13818-6 (part 6 of the MPEG-2 standard).
DSM-CC may work in conjunction with next generation packet networks, working alongside such internet protocols as RSVP
Resource Reservation Protocol
The Resource Reservation Protocol is a Transport Layer protocol designed to reserve resources across a network for an integrated services Internet. RSVP operates over an IPv4 or IPv6 Internet Layer and provides receiver-initiated setup of resource reservations for multicast or unicast data flows...
, RTSP, RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
and SCP
Secure copy
Secure Copy or SCP is a means of securely transferring computer files between a local and a remote host or between two remote hosts. It is based on the Secure Shell protocol....
. Although DSM-CC is usually associated with video delivery (via satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
or terrestrially) and with interactive content, it is also used among audio servers and clients. The architecture describes three main parts of the system: the client
Client (computing)
A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....
, the server
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
, and the session resource manager (SRM). The server provides content and other services to the client, and both are "clients" of the SRM. The SRM allocates and manages network resources (such as channels
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...
, bandwidth
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
, and network address
Network address
Network address may refer to:*Base address*Classful address*IP address*IPX address*Logical address*Network layer address,*X.25/X.21 address*MAC address-See also:*Autonomous system *Host address*Link layer*Subnet mask...
es.) By combining server and client components together onto the same platforms, peer-to-peer
Peer-to-peer
Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
content access and delivery systems can be constructed.
These specifications include numerous implementation options. For example, MPEG-2 video can be encoded in different ways, and a DSM-CC system can be constructed to include or exclude certain features and interfaces. Normally, an outside specification will define a profile of specific options, allowing systems built using common profiles to interoperate.
DSM-CC defines or extends five distinct protocols:
User-User: Allows remote access by the client to objects on the server. The User-User specification goes beyond the definition of specific server object classes to define classes local to the client, as well as some of the interaction with other parts of the system. The distributed object model is based on CORBA
Çorba
Chorba , ciorbă , shurpa , shorpo , or sorpa is one of various kinds of soup or stew found in national cuisines across Middle East...
. Objects are accessed using the internet inter-ORB protocol (IIOP), with some optional extensions. Two subsets, "core" and "extended", are defined. In the model, some clients may also load content onto the server.
User-Network: There are two parts to this protocol: Session and Resource. This protocol is used between the client and SRM, and between the server and SRM. The U-N Session protocol is used to establish sessions with the network, associated with resources with are allocated and released using the U-N Resource protocol.
MPEG transport profiles: The specification provides profiles to the standard MPEG transport protocol (defined by ISO/IEC 13818-1) to allow transmission of event, synchronization, download, and other information in the MPEG transport stream.
Download: Several variations of this protocol allow transfer of content from server to client, either within the MPEG transport stream or on a separate (presumably high-speed) channel. Flow-controlled download allows the download operations to be negotiated and controlled by the client. A variation of download is an autonomous "data carousel" on the server which repeatedly downloads information; the download carousel client waits for the information without initiating the transfer. An extension to the data carousel is the "object carousel", which presents downloaded information as objects compatible with the objects defined by the User-User API. (The choice of download or IIOP protocols is embedded in the object's IOR, so the means of access is transparent to the client application.)
Switched Digital Broadcast-Channel Change Protocol (SDB/CCP): Enables a client to remotely switch from channel to channel in a broadcast
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
environment. Used to attach a client to a continuous-feed session (CFS) or other broadcast feed. Sometimes used in pay-per-view
Pay-per-view
Pay-per-view provides a service by which a television audience can purchase events to view via private telecast. The broadcaster shows the event at the same time to everyone ordering it...
.
An implementation does not always need all of these protocols. Almost all implementations in the real world use a subset.
Extension
Delivery Multimedia Integration FrameworkDelivery Multimedia Integration Framework
DMIF, or Delivery Multimedia Integration Framework, is a uniform interface between the application and the transport, that allows the MPEG-4 application developer to stop worrying about that transport. DMIF was defined in MPEG-4 Part 6 in 1999. DMIF defines two interfaces: the DAI and the DNI...
(DMIF) expands upon the MPEG-2 DSM-CC standard (ISO/IEC 13818-6:1998) to enable the convergence of interactive, broadcast and conversational multimedia into one specification which will be applicable to set tops, desktops and mobile stations. The DSM-CC work was extended as part of the ISO/IEC 14496-6 (MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
Part 6), with the DSM-CC Multimedia Integration Framework (DMIF).
External links
- ISO/IEC 13818-6:1998 - Information technology -- Generic coding of moving pictures and associated audio information - Part 6: Extensions for DSM-CC
- How To Become An Expert In DSM-CC - DSM-CC from the perspective of IDTV
- ISO DSM-CC FAQ
- ISO DSM-CC Introduction
- OpenCaster free GPL licensed software for transport stream broadcasting supporting DSM-CC