Differences between version 7 and previous revision of MPEGTerminology.
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| Newer page: | version 7 | Last edited on Saturday, January 9, 2010 7:18:31 pm | by LawrenceDoliveiro | Revert |
| Older page: | version 6 | Last edited on Saturday, January 9, 2010 5:58:48 pm | by LawrenceDoliveiro | Revert |
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Not every PES packet has to have a PTS, but there must be at least one every 0.7 seconds, in order to ensure the decoder clock stays in sync. The PTS is a 33-bit unsigned integer, in units of a 90kHz clock.
A packet belonging to one stream (say, video) will invariably be immediately followed by one belonging to another stream (say, audio), with around the same PTS. This interleaving or ''multiplexing'' of data from different streams minimizes the amount of buffering the decoder has to implement in order to provide smoothly synchronized playback.
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+MPEG defines standard stream types for audio and video. Besides these, it also allows for ''padding'' streams (the contents of which are ignored by the decoder), and ''private'' streams, not further specified by MPEG itself. For instance, [DVDVideo] defines meanings for the contents of particular private streams.
An MPEG file/bytestream could just consist of an unadorned sequence of PES packets, but this is not usually done. Instead, MPEG is normally represented in either ''transport stream'' (MPEG-TS) or ''program stream''(MPEG-PS) formats.
In transport stream format, the PES packets are sliced into small pieces, each of which is carried in a transport-stream packet. This is intended for use in transmission over less-than-fully-reliable channels (e.g. broadcast over the air), where a momentary burst of interference or loss of signal will only lose some transport-stream packets.
