[FFmpeg-devel] [Bounty] Impl. check if input h264 P/B frame ref's frame prior to last I

[Carl Eugen Hoyos]

Andrey Utkin <andrey_utkin <at> fastmail.com> writes:

> 
> On Mon, 22 Feb 2016 17:23:06 +0000 (UTC)
> Carl Eugen Hoyos <cehoyos <at> ag.or.at> wrote:
> 
> > Andrey Utkin <andrey_utkin <at> fastmail.com> writes:
> > 
> > > As it was discussed today on #ffmpeg and #ffmpeg-devel, 
> > > only IDR frames are considered safe seek points by design 
> > > of H.264.  
> > 
> > Since valid H264 streams without IDR (and without I) frames 
> > exist, this cannot be true.
> 
> Haven't heard of such streams, but let's take it granted. Why does it
> mean that above statement is false? If there's no IDR frames, then
> it is safe to assume that this stream has no seek points guaranteed to
> be valid (unless we introspect the references between frames). I don't
> see anything wrong with such statement.

Sorry for being unclear:
Since valid, useful H264 streams with many ("safe") seek points 
but without I or IDR frames exist, the statement "only IDR frames 
are safe seek points" can't be true.

Carl Eugen