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<div class="moz-cite-prefix">On 11/23/2013 12:05 AM, Don Moir wrote:<br>
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----- Original Message ----- <br>
From: Andy Shaules <br>
To: This list is about using libavcodec, libavformat,
libavutil,libavdevice and libavfilter. <br>
Sent: Saturday, November 23, 2013 12:55 AM<br>
Subject: Re: [Libav-user] packet flag AV_PKT_FLAG_KEY</div>
<div> </div>
<div><br>
On 11/22/2013 7:47 PM, Don Moir wrote:</div>
<div> </div>
<div>>>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.</div>
<div> </div>
<div>>>Is it not a application flag ?</div>
<div> </div>
<div>>>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 :)</div>
<div> </div>
<div>>>What if there are no index_entries ? Whats a key
packet then and how to determine ?</div>
<div> </div>
<div>>>Just trying to clear up my own confusion with
this.</div>
<div> </div>
<div> </div>
<div>>For h264, the key frame network abstraction unit of
the packet will be of type IDR, instant data refresh. <br>
>I believe NAL type 5. </div>
<div> </div>
<div>Thanks Andy. </div>
<div> </div>
<div>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.</div>
<div> </div>
<div>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.</div>
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Imagine H264 at HD resolution with 5 or 6 horizontal slices where
the key frame only equals one horizontal strip of macro blocks. So
yes, it may or may not be a full key frame, but it should be an IDR
packet.<br>
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