[FFmpeg-devel] meaning of AV_PKT_FLAG_KEY

Don Moir donmoir at comcast.net
Wed Dec 4 13:57:05 CET 2013

----- 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 ?. 

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