[FFmpeg-devel] [RFC] mpegts: Provide a monotonic timestamp to the outside world

Michael Niedermayer michaelni at gmx.at
Tue Oct 23 03:59:36 CEST 2012

On Mon, Oct 22, 2012 at 11:39:34PM +0200, Harald Axmann wrote:
> On 22.10.2012 16:38, Joakim Plate wrote:
> >I do agree that that would be optimal. But it's very unlikely a
> >patch for a
> >complete solution  will surface anytime soon since it will get so
> >much more
> >complex.
> >
> >Unless Harald Axmann is up for the task, I suppose we'll have to keep
> >something like this in our local clone of ffmpeg for the time being.
> >mpegts is mostly used for broadcast in our use case, and recordings
> >longer than the timestamp wrapping are very very unlikely, while
> >wrapping once somewhere in them are likely.
> What I could do is have a look if it is possible to change XBMC's
> seeking algorithm to a byte-based version for file formats allowing
> discontinuities. Perhaps this would be the cleanest solution for
> XBMC. But I'm afraid, I definitely don't have enough time to
> implement the mentioned perfect solution. This would be surely a
> tough piece of work.
> But just as a fundamental question: Is there any reason to keep the
> original time stamp, as Hendrik Leppkes requested. What is the
> benefit? IMHO the TS time stamp is arbitrary and it does not matter,
> if an offset is applied or not, as long as the final value is
> wrapped again with 33 bits. The important thing seems to be the
> relation of the DTS and the PTS to the PCR. With the proposed patch
> all files should be playable as before, even if the time stamp saved
> at the beginning for correction is wrong. For any TS discontinuity
> or whatever the behavior would be identical to the current one.

assume you have external references to timestamps, or you want to
cut and then merge pieces of TS without timestamps changing
or you have a audio and a video TS file and want them syncronized
against each other (assuming their timestamps allow this)
i guess there are many other cases ...

> But it would make things easier for XBMC and perhaps also for other
> applications as long as we don't have a perfect solution. After all
> I must say, that time-based search really works great on DVB MPEG-TS
> files, as they generally have nice monotonic time stamps.

I dont mind having a non perfect solution compared to no solution,
but it has to be optional and it should not be mpegts specific.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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