[FFmpeg-devel] [PATCH 2/2] ffmpeg: bump the intra stream discontinuity message to warning

[Jan Ekström]

On Thu, Oct 11, 2018 at 10:50 PM Marton Balint <cus at passwd.hu> wrote:
> On Thu, 11 Oct 2018, Michael Niedermayer wrote:
>
> > On Wed, Oct 10, 2018 at 02:10:26AM +0300, Jan Ekström wrote:
> >> As libavformat should at this point be handling general input
> >> timestamp discontinuities for us - such as with MPEG-TS - the
> >> amount of messages from this case should be small, and if it
> >> does start spamming messages, that would be a sign that either
> >> the input, or the discontinuity handling code itself is broken.
> >
> > libavformat handles the case where a timestamp wraps around
> > that is goes beyond the maximum value. Thats not the only
> > type of discontinuity. Is there some code i am missing or that
> > i forgot about ?
>
> FWIW libavformat only handles wraparound _once_.
>
> Regards,
> Marton

Looking at update_wrap_reference and where it gets called from et al,
it would seem like it should take care of multiple as it keeps
updating the reference and applying wrap-around as required?

Generally the one in ffmpeg.c seemed to only get hit when there was
some sort of jump in the timestamps in addition to the wrap-arounds -
or if the lavf wrap-around logic decided to go follow a teletext track
with utterly broken timestamps as the reference.

As for the comment, yes - lavf's wrap-around logic doesn't try to poke
all sorts of discontinuities, but in my opinion the fact that "casual"
discontinuities should no longer happen at this stage definitely makes
logging that a discontinuity happened and that we tried to apply a new
offset to all streams worth mentioning on a more normal verbosity
level than "debug". Currently you will never, ever hear anything about
this logic activating unless your verbosity level is ridiculously
high. And as a general case, if the logic is working correctly this
code should only fire once per discontinuity, not in an eternal loop.

Best regards,
Jan