----- Original Message -----
From: "Roger Pack" <[email protected]>
To: "This list is about using libavcodec, libavformat, libavutil,libavdevice
and libavfilter." <[email protected]>
Sent: Thursday, August 02, 2012 2:48 PM
Subject: Re: [Libav-user] Why does av_seek_frame() not seek to a keyframe?
I believe that does no seeking there. Putting -ss after the input will
cause
ffmpeg to demux up to the requested timestamp, so it's not quite related
to
seeking (putting -ss before the input will seek the input file).
Since -a/vcoded copy avoids re-encoding, it just copies the packets
(without
regard to keyframes, iiuc). The packet closest to 90 seconds probably
isn't
a keyframe, but since that's where you requested the start it ffmpeg
starts
copying packets from there anyway.
Yes I would totally agree with you, except I can't find a single "-ss"
time that seems to "accidentally hit an i-frame" and work the way you
and I would expect it to...though I haven't looked into it much...
-r
Given that seeking on mpeg2video does not seek to a key frame unless you get
lucky.
I did a couple of test and normally for mpeg2video the first frame read
after a seek is not a key frame which causes a delay in the animiation. Then
I seeked to known keyframe times and that seems to successfully seek to a
key frame. I did this a couple times. For testing, I got the known keyframe
times by looking at the data after a seek.
So when seeking backward you should always be at a keyframe at or before
your requested time but in the case of mpeg2video it does not happen.
o - Is there an intent to get this reported as a bug if not already ?
o - If it is reported as a bug, whats the likelyhood it will be fixed ? I
think I saw somewhere that it has been known for sometime or something to
that effect.
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