[FFmpeg-devel] [PATCH 2/3] flvdec: Mark the demuxer as allowing discontinuous timestamps

[Michael Niedermayer]

On Thu, Nov 22, 2018 at 10:27:18AM +0000, Derek Buitenhuis wrote:
> On 22/11/2018 02:16, Michael Niedermayer wrote:
> > the specification says this:
> > "Timestamp UI24 Time in milliseconds at which the data in this tag
> >                 applies. This is relative to the first tag in the FLV file,
> >                 which always has a timestamp of 0.
> > "
> > So flv does not seem to allow discontinuities. Any tool writing files with
> > discontinuities would be faulty
> 
> I know they're not valid, however in the real world, tons and tons of these files
> exists, since this is how live FLV is done quite often.
> 
> > declaring files which have no discontinuities as having some would
> > result in worse performing seeking in some cases. Both slower and or less
> > accurate. Also flv IIRC allows gaps in tracks like no packets where there is
> > silence. This may interfere with discontinuities as it looks
> > like a discontinuity.
> 
> I agree, but then how do you propose we handle FLVs that do have discontinuites?
> Currently the demuxer just outputs the discontinuiting (negative or positive),
> and it breaks, since codebases expect that demuxers which do this will be properly
> marked with the DISCONT flag.
> 

> > Can these files with discontinuities be detected somehow from the headers?
> > If so then the probe function could be changed so they get the discontinuity
> > flag while valid files do not have the disadvantages from having it set
> 
> As far as I am aware, no, they cannot be detected by header. FLV is crappy like that.

do we have some sample flv files that require this patchset / that have
discontinuites.

another thing i just realize now, why is this discontinuity issues coming up
now? flv support is very old. This should be a long standing issue 

thanks

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Take away the freedom of one citizen and you will be jailed, take away
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