[Libav-user] packet flag AV_PKT_FLAG_KEY

Don Moir donmoir at comcast.net
Sat Nov 23 09:05:02 CET 2013

----- Original Message ----- 
From: Andy Shaules 
To: This list is about using libavcodec, libavformat, libavutil,libavdevice and libavfilter. 
Sent: Saturday, November 23, 2013 12:55 AM
Subject: Re: [Libav-user] packet flag AV_PKT_FLAG_KEY

On 11/22/2013 7:47 PM, Don Moir wrote:

>>Not sure what AV_PKT_FLAG_KEY is supposed to mean. The assumption to me early on is it represented a key frame but not necessarily.

>>Is it not a application flag ?

>>Seems for at least H264 it doesnt have much meaning to application. If the packet dts value is in the stream index_entires then that represents a key frame for sure ( hopefully :)

>>What if there are no index_entries ? Whats a key packet then and how to determine ?

>>Just trying to clear up my own confusion with this.

>For h264, the key frame network abstraction unit of the packet will be of type IDR, instant data refresh. 
>I believe NAL type 5. 

Thanks Andy. 

Dont see that info in a packet. Only thing relevant that changes is the flags member (0 or 1). Now frame may contain additional info after decoding but it's documented that AV_PKT_FLAG_KEY represents a keyframe.

If it is for internal use, a different flag should have been used the way I see it. So trying to understand what the real intended use of AV_PKT_FLAG_KEY is.
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