[Libav-user] Frames are not visually lining up between my code and ffmpeg.exe

[Simon Daniels]

Hi Michael -- after reading into things a bit more, I agree that it's risky
what I'm doing. However, I only need about 3 frames per second so maybe
waiting for a key frame isn't the end of the world...

Is there a safer way? The decoding is extremely expensive so I only want to
do it when I absolutely need to.

Thanks!


On Tue, Jun 26, 2012 at 11:44 AM, Michael Bradshaw <
mbradshaw at sorensonmedia.com> wrote:

> On Tue, Jun 26, 2012 at 12:34 PM, Simon Daniels
> <simondaniels23 at gmail.com> wrote:
> > // Is this a packet from the video stream?
> > if (packet.stream_index == videoStreamIndex && frameLocation++ %
> frameSkip
> > == 0)
> > {
> > // Decode video frame
> > avcodec_decode_video2(pCodecCtx, pFrameYUV, &isFrameFinished, &packet);
>
> You don't want to be doing it like this, I don't think. If there are B
> frames in the video, this could really mess things up (because frame 2
> could depend on decoding frame 1 just before it, but you skipped
> decoding frame 1, so now frame 2 is junk/gets decoded wrong (and now
> all the ones decoded after it will be junk frames too until you hit a
> keyframe)).
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