[gstreamer-bugs] [Bug 583875] adding variants to mpegtsmux

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-bad | Ver: 0.10.22




------- Comment #3 from Jan Schmidt  2009-05-26 15:35 UTC -------
OK. I don't know enough about the differences between the the MPEG-TS types to
decide whether it's really worthwhile having 3 separate elements registered by
the plugin. I agree that it's the cleanest approach to this general class of
problems though - I like how it's worked out for qtmux.

As for the specific variants, I know that m2ts/AVCHD seems to just be standard
MPEG-TS with the addition of a 4 byte timestamp (checksum?) between each frame.
typefinding detects this and puts it in the caps as 'video/mpegts,
systemstream=(boolean)true, packetsize=(int)192'.

At the moment mpegtsdemux takes the packetsize from the caps and just ignores
these extra timestamp bytes. I've seen some indication that it may fail
spectacularly on some streams with this approach. That is, Wikipedia says the
extra timestamp bytes are used to for indicating out-of-order packets, and that
suggests the demuxer may need to reorder the incoming data stream to correctly
demux it:
http://en.wikipedia.org/wiki/MPEG-2_transport_stream#Modifications_of_transport_stream_specification_for_random-access_media_.28M2TS.29

I think HDV also uses this 192 byte scheme?

I know there is also a 204-byte MPEG-TS variant, 188-byte standard payload plus
16 bytes error correction code, used in DVB-ASI, and a 208 byte variant for
ATSC (188-byte payload plus 20 byte forward error correction code):
http://en.wikipedia.org/wiki/MPEG-2_transport_stream#Packet

If all the above is correct, I think you're talking about 4 possible MPEG-TS
muxer variants, only 2 of which we can generate at the moment.


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