[Libav-user] Updated libav/ffmpeg tutorial

Max Vlasov max.vlasov at gmail.com
Tue Mar 3 16:01:12 CET 2015

On Tue, Mar 3, 2015 at 2:47 PM, wm4 <nfxjfg at googlemail.com> wrote:

> On Tue, 3 Mar 2015 12:27:51 +0300
> Max Vlasov <max.vlasov at gmail.com> wrote:
> >
> > It turns out that it is just a get accessor for best_effort_timestamp
> field
> > and the corresponding set accessor (av_frame_set_best_effort_timestamp)
> is
> > called twice (in avcodec_decode_video2 and in avcodec_decode_audio4) in
> the
> > utils.c with a similar lines
> As I said, it's only a helper. What you really should do is always
> using the PTS, and if the PTS is not available, use the DTS. The extra
> heuristics are useful only for broken files and such; and they can be
> better than what best_effort_timestamp does.

You probably mean pkt_pts, pkt_dts from the frame, right? At least I see
that this values used by this simple function (guess_correct_pts) as
incoming data for comparison. And also quick test shows that
best_effort_timestamp is equal to (if pkt_pts valid then pkt_pts else
pkt_dts) value most of the time.

I also see that guess_correct_pts is the mutating function relying on the
statistics of decoding which might be different for different seek/play

So it looks like best_effort_timestamp not so great after all, but It's
strange that no simple function was implemented so far to implement this
simple conditional (pkt_pts first, pkt_dts next).
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