Program stream
Encyclopedia
Program stream is a container format for multiplexing
digital audio
, video
and more. The PS format is specified in MPEG-1
Part 1 (ISO/IEC 11172-1) and MPEG-2
Part 1, Systems (ISO/IEC standard 13818-1/ITU-T H.222.0). The MPEG-2 Program Stream is analogous and similar to ISO/IEC 11172 Systems layer and it is forward compatible.
Program streams are used on DVD-Video
discs and HD DVD
video discs, but with some restrictions and extensions. The filename extensions are VOB
and EVO
respectively.
s (PES), which have a common time base, into a single stream. It is designed for reasonably reliable media such as disks, in contrast to MPEG transport stream which is for data transmission in which loss of data is likely. Program streams have variable size records and minimal use of start codes which would make over the air reception difficult, but has less overhead. Program stream coding layer allows only one program of one or more elementary streams to be packaged into a single stream, in contrast to transport stream, which allows multiple programs.
MPEG-2 Program stream can contain MPEG-1 Part 2 video, MPEG-2 Part 2 video, MPEG-1 Part 3 audio (MP3, MP2
, MP1
) or MPEG-2 Part 3 audio. It can also contain MPEG-4 Part 2
video, MPEG-2 Part 7 audio (AAC
) or MPEG-4 Part 3 (AAC) audio, but they are rarely used. The MPEG-2 Program stream has provisions for non-standard data (e.g. AC-3
audio or subtitles) in the form of so-called private streams. International Organization for Standardization authorized SMPTE Registration Authority, LLC as the registration authority for MPEG-2 format identifiers. It publishes list of compression formats which can be encapsulated in MPEG-2 transport stream and program stream.
you will see the following structure.
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...
digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
, video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
and more. The PS format is specified in MPEG-1
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...
Part 1 (ISO/IEC 11172-1) 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...
Part 1, Systems (ISO/IEC standard 13818-1/ITU-T H.222.0). The MPEG-2 Program Stream is analogous and similar to ISO/IEC 11172 Systems layer and it is forward compatible.
Program streams are used on DVD-Video
DVD-Video
DVD-Video is a consumer video format used to store digital video on DVD discs, and is currently the dominant consumer video format in Asia, North America, Europe, and Australia. Discs using the DVD-Video specification require a DVD drive and a MPEG-2 decoder...
discs and HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...
video discs, but with some restrictions and extensions. The filename extensions are VOB
VOB
A VOB file is a container format in DVD-Video media. VOB can contain video, audio, subtitle, menu and navigation contents multiplexed together into a stream form. VOB is based on the MPEG program stream format, but with additional limitations and specifications in the private streams...
and EVO
Enhanced VOB
An EVO file is a container format contained in HD DVD video media. It contains the actual video, audio, subtitle and menu contents in stream form. It is an extension to VOB, which is an extension to MPEG program stream...
respectively.
Coding structure
Program streams are created by combining one or more Packetized Elementary StreamPacketized Elementary Stream
Packetized Elementary Stream is a specification in the MPEG-2 Part 1 and ITU-T H.222.0 that defines carrying of elementary streams in packets within MPEG program stream and MPEG transport stream...
s (PES), which have a common time base, into a single stream. It is designed for reasonably reliable media such as disks, in contrast to MPEG transport stream which is for data transmission in which loss of data is likely. Program streams have variable size records and minimal use of start codes which would make over the air reception difficult, but has less overhead. Program stream coding layer allows only one program of one or more elementary streams to be packaged into a single stream, in contrast to transport stream, which allows multiple programs.
MPEG-2 Program stream can contain MPEG-1 Part 2 video, MPEG-2 Part 2 video, MPEG-1 Part 3 audio (MP3, MP2
MPEG-1 Audio Layer II
MPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III...
, MP1
MPEG-1 Audio Layer I
MPEG-1 Audio Layer I, commonly abbreviated to MP1, is one of three audio formats included in the MPEG-1 standard. While supported by most media players, the codec is considered largely outdated, and replaced by MP2 or MP3....
) or MPEG-2 Part 3 audio. It can also contain MPEG-4 Part 2
MPEG-4 Part 2
MPEG-4 Part 2, MPEG-4 Visual is a video compression technology developed by MPEG. It belongs to the MPEG-4 ISO/IEC standards. It is a discrete cosine transform compression standard, similar to previous standards such as MPEG-1 and MPEG-2...
video, MPEG-2 Part 7 audio (AAC
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
) or MPEG-4 Part 3 (AAC) audio, but they are rarely used. The MPEG-2 Program stream has provisions for non-standard data (e.g. AC-3
AC-3
AC-3 can be:* AC-3 algorithm , one of a series of algorithms used for the solution of constraint satisfaction problems* Comte AC-3, a 1920s Swiss bomber/transport aircraft.* Dolby AC-3, a Dolby Digital, audio codec...
audio or subtitles) in the form of so-called private streams. International Organization for Standardization authorized SMPTE Registration Authority, LLC as the registration authority for MPEG-2 format identifiers. It publishes list of compression formats which can be encapsulated in MPEG-2 transport stream and program stream.
Coding details
If you open up an unencrypted VOB file or other program stream with a hex editorHex editor
A hex editor is a type of computer program that allows a user to manipulate the fundamental binary data that makes up computer files. Note that computer files can be very small to very large...
you will see the following structure.
| Name | Number of bit Bit A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states... s |
Description |
|---|---|---|
| sync bytes | 32 | 0x000001BA |
| marker bits | 2 | 01b Binary numeral system The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2... |
| System clock [32..30] | 3 | System Clock Reference (SCR) bits 32 to 30 |
| marker bit | 1 | 1 Bit always set. |
| System clock [29..15] | 15 | System clock bits 29 to 15 |
| marker bit | 1 | 1 Bit always set. |
| System clock [14..0] | 15 | System clock bits 14 to 0 |
| marker bit | 1 | 1 Bit always set. |
| SCR extension | 9 | |
| marker bit | 1 | 1 Bit always set. |
| bit rate Bit rate In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time.... |
22 | In units of 50 bytes per second. |
| marker bits | 2 | 11 Bits always set. |
| reserved | 5 | reserved for future use |
| stuffing length | 3 | |
| stuffing bytes | 8*stuffing length | |
| system header (optional) | 0 or more | if system header start code follows: 0x000001BB |
| Name | Number of bytes |
Description |
|---|---|---|
| sync bytes | 4 | 0x000001BB |
| header length | 2 | |
| rate bound and marker bits | 3 | |
| audio bound and flags | 1 | |
| flags, marker bit, and video bound | 1 | |
| Packet rate restriction and reserved byte | 1 |
External links
- MPEG-2
- Official MPEG web site
- BBC On MPEG
- RFC 3555 - MIME Type Registration of RTP Payload Formats (video/MP2P, video/MP1S)