Packetized Elementary Stream (PES) is a specification in the MPEG-2 Part 1 (Systems) (ISO/IEC 13818-1) that defines carrying of elementary streams in packets within MPEG program stream and MPEG transport stream.[1] The elementary stream is packetized by encapsulating sequential data bytes from the elementary stream inside PES packet headers.
A typical method of transmitting elementary stream data from a video or audio encoder is to first create PES packets from the elementary stream data and then to encapsulate these PES packets inside Transport Stream (TS) packets or Program Stream (PS). The TS packets can then be multiplexed and transmitted using broadcasting techniques, such as those used in an ATSC and DVB.
Transport Streams and Program Streams are each logically constructed from PES packets. PES packets shall be used to convert between Transport Streams and Program Streams. In some cases the PES packets need not be modified when performing such conversions. PES packets may be much larger than the size of a Transport Stream packet.[1]
Contents |
PES packet header
| Name | Size | Description |
|---|---|---|
| Packet start code prefix | 3 bytes | 0x000001 |
| Stream id | 1 byte | Examples: Audio streams (0xC0-0xDF), Video streams (0xE0-0xEF) [2] [3] [4] [5] |
| Note: The above 4 bytes is called the 32 bit start code. | ||
| PES Packet length | 2 bytes | Can be zero.If the PES packet length is set to zero, the PES packet can be of any length. A value of zero for the PES packet length can be used only when the PES packet payload is a video elementary stream.[6] |
| Optional PES header | variable length | |
| Stuffing bytes | variable length | |
| Data | See elementary stream. In the case of private streams the first byte of the payload is the sub-stream number. |
Optional PES header
| Name | Number of Bits | Description |
|---|---|---|
| Marker bits | 2 | 10 binary or 0x2 hex |
| Scrambling control | 2 | 00 implies not scrambled |
| Priority | 1 | |
| Data alignment indicator | 1 | 1 indicates that the PES packet header is immediately followed by the video start code or audio syncword |
| Copyright | 1 | 1 implies copyrighted |
| Original or Copy | 1 | 1 implies original |
| PTS DTS indicator | 2 | 11 = both present, 10 = only PTS |
| ESCR flag | 1 | |
| ES rate flag | 1 | |
| DSM trick mode flag | 1 | |
| Additional copy info flag | 1 | |
| CRC flag | 1 | |
| extension flag | 1 | |
| PES header length | 8 | gives the length of the remainder of the PES header |
| Optional fields | variable length | presence is determined by flag bits above |
| Stuffing Bytes | variable length | 0xff |
References
- ^ a b ISO (2000-12-01) ISO/IEC 13818-1 : 2000, Second edition, Retrieved on 2009-07-25
- ^ http://www.dvb.org/technology/standards/a001r7.tm1214r30.dTS101154.v1.8.1.pdf>
- ^ Method and apparatus for changing codec to reproduce video and/or audio data streams encoded by different codecs within a channel - Patent EP1827030
- ^ European publication server
- ^ https://publications.european-patent-office.org/PublicationServer/document.jsp?PN=EP1827030%20EP%201827030&iDocId=6296342&iFormat=0
- ^ http://happy.emu.id.au/lab/tut/dttb/dtbtut4b.htm#s4p4>
External links
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