[vlc] Re: mpeg2-ts timestamping

[Måns Rullgård]

GALAD77 <GALAD77 at terra.es> writes:

> I would like to be able at playing to set the time the video was
> encoded. The time filter of VLC can help a bit, but I need to include
> some extra information. The time must not necessarily be inserted into
> the video via GDI or something else, but into the MPEG2-TS frame format
> in some manner that it can be deencapsulated at decoding.
> But as far as I know there is no optional field in MPEGTS with enough
> size (say 48 bits) to store the time, for example with a time(NULL) command.
> Another way would be to multiplex the data within the MPEG2-TS frame,
> but it adds complexity.

There are a few places you could possibly use.  You could, for
instance, put a custom descriptor in the PMT.  Another possibility is
to hijack the original_pcr field (42 bits).  It is only used in some
special operations, and as long as you don't do anything that requires
sane values there, you should be fine, although, strictly speaking,
your stream will be invalid.

> Above all, the MPEG2-TS encapsulation standard, or drafts, are a bit
> large and difficult to understand, so I have asked for a simpler
> tutorial that explains the basics in a clear manner so that acting in
> the source code can be more agile.

Believe it or not, the text in the standard is pretty much as simple
as it gets.  For these purposes, you can safely skip the sections
about buffering, which can otherwise be quite a mouthful.

-- 
Måns Rullgård
mru at inprovide.com

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