[FFmpeg-devel] meaning of AV_PKT_FLAG_KEY

Michael Niedermayer michaelni at gmx.at
Wed Dec 11 12:45:39 CET 2013

On Wed, Dec 04, 2013 at 07:57:05AM -0500, Don Moir wrote:
> ----- Original Message ----- From: "Don Moir" <donmoir at comcast.net>
> To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> Sent: Wednesday, December 04, 2013 7:18 AM
> Subject: Re: [FFmpeg-devel] meaning of AV_PKT_FLAG_KEY
> >
> >>----- Original Message ----- From: "Michael Niedermayer"
> >><michaelni at gmx.at>
> >>To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> >>Sent: Tuesday, December 10, 2013 7:49 PM
> >>Subject: Re: [FFmpeg-devel] meaning of AV_PKT_FLAG_KEY
> >
> >
> >>On Wed, Dec 04, 2013 at 07:44:53AM -0500, Don Moir wrote:
> >>>I asked about this 2 years ago in ticket and no answer there.
> >>>
> >>>I asked in user and no answer there.
> >>>
> >>>So asking here what is the meaning of AV_PKT_FLAG_KEY and does it have any meaining to an application ?
> >>>
> >>>The comment for AV_PKT_FLAG_KEY says it represents a key
> >>>packet. If you decode this packet, the frame indicates it's a
> >>>key frame.
> >>>
> >>>If packet contains AV_PKT_FLAG_KEY it does not necessarily
> >>>reflect a timestamp in index_entries which are known to be
> >>>keyframes if marked as such.
> >>>
> >>>Would be damn useful is this flag was dependable as a keyframe
> >>>or start of keyframe. Right now I don't know if its a bug or
> >>>what it is supposed to mean.
> >
> >>it means its a keyframe in the sense of a frame from which you can
> >>start decoding
> >
> >Thats what I have been assuming it means more or less but wasn't
> >quite sure. This was brought on by AVDISCARD_NONKEY not working
> >across the board. AVDISCARD_NONKEY works much better now for h264
> >and the like, but still not reliable for others, so not a good
> >general solution.
> >
> >At least now I will know if  AV_PKT_FLAG_KEY is not working as expected, it's a bug :)
> >
> >Thanks.
> >
> Forgot to ask but is there a reason packets marked with
> AV_PKT_FLAG_KEY are not added to the index_entries ? I mean if you
> can start decoding from there does it make sense ?.

its up to each demuxer if it uses the index_entries structure

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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