[Libav-user] Save frame to jpg with data from avcodec_decode_video2

Simon Daniels simondaniels23 at gmail.com
Tue Jun 26 17:50:11 CEST 2012


Works perfectly Alex! Thanks!

Carl -- I'll start a separate thread on the frame count inconsistencies.

On Tue, Jun 26, 2012 at 3:59 AM, Alex Cohn <alexcohn at netvision.net.il>wrote:

> On Tue, Jun 26, 2012 at 12:00 PM, Camera Man
> <i.like.privacy.too at gmail.com> wrote:
> > On 06/26/2012 04:13 AM, Alex Cohn wrote:
> >
> >> On Tue, Jun 26, 2012 at 9:18 AM, Simon Daniels <
> simondaniels23 at gmail.com>
> >> wrote:
> >>>
> >>> I don't want to use the ffmpeg command-line to save out the frames
> >>> because
> >>> for some reason the frame counts are not matching. Ffmpeg.exe saves
> more
> >>> frame jpegs than avcodec_decode_video2 seems to find.See an old thread
> >>
> >>
> >>
> http://libav-users.943685.n4.nabble.com/Save-AVFrame-to-jpg-file-td2314979.html
> >
> >
> > I've been using that code successfully. I've done a git pull recently,
> and
> > noticed that the encoders (including mjpegs) are now frame/slice
> multithread
> > capable. Does this mean it's possible that the return from
> > avcodec_encode_video2 is somehow pipelined for mjpeg?
> >
> > That is, when calling avcodec_decode_video2(), you put in a packet, you
> get
> > a frame, but the frame might be related to an earlier packet (either
> because
> > of I/P/B/reference frame reordering, or because of a multithreaded
> decoder).
> >
> > Is it possible that when calling avcodec_encode_video2() for mjpeg, you
> will
> > receive an encoded packet which is related to an earlier frame because of
> > the new multithreading infrastructure?
>
> To the best of my knowledge, with multithreading you are still
> expected to receive results in correct order, but the delay may be
> effected.
>
> BR,
> Alex Cohn
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