[Matroska-devel] New Matroska field: extra broadcast data
jerome at mediaarea.net
Thu Sep 24 20:00:07 CEST 2015
Le 23/09/2015 18:13, Steve Lhomme a écrit :
> In addition to close caption, broadcasting often carries data in some
> non displayed pixels, especially in analog videos. We should be able
> to store those invisible information in the container as well.
> The first that comes to might is Teletext in Europe. There might be others.
I think to:
- VBI raw content (dump of non visible part of a video stream, and
should sometimes not be lossy compressed, so not in the compressed video
stream directly), which can contain SMPTE ST-12 timecodes (real time
codes, not timestamps ;-) ), CEA-608 captions...
- VANC (SMPTE ST-291, we must be careful because there are 10-bit /
synchro bytes / checksum "options", because MXF uses 8-bit +no synchro
bytes + no checksum , GXF uses 10-bit + no synchro bytes + checksum, LXF
uses 8-bit + synchro bytes + checksum, if we define VANC in Matroska we
need to say how we transport it), which can contain SMPTE ST-12
timecodes, CEA-608 captions, CDP, Bar data, Teletext (WST actually),
Acquisition Metadata (SMPTE RDD 18)...
- CDP from a serial link (captions only).
BTW, same issue with "Teletext": Teletext can contain a programs list +
subtitles in the same track.
> Given it's in the video frames it should probably be a kind of
> track(s). We already extract the closed caption. We could extra some
> others with different "codec" and/or keep the rest of the data raw to
> be handled by other processes, outside of the scope of Matroska.
Isn't TrackType = 3 (Complex) enough for that?
and we try to define C_VBI, C_VANC, C_TELETEXT... codec identifiers.
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