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Old 4th July 2012, 02:55   #1  |  Link
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how to judge the key frame in h264 stream

Dear all,

Is there a simple way to judge whether a h264 frame is a key
frame or not?

If not, is there any document that I can use to solute this

thanks in advance,
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Old 4th July 2012, 07:05   #2  |  Link
Dust Signs
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IDR pictures (NAL unit type 5) are always key pictures. I pictures can be key pictures, but do not have to be, since the pictures after it may be predicted from pictures coded before the I picture. Sometimes, recovery point SEI messages (NAL unit type 6 with SEI payload type 6) are present which indicate that I pictures are actually key pictures, but you can't rely on the existence of these SEI messages since they are optional.

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Old 4th July 2012, 08:03   #3  |  Link
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Aside from the above, of which I was blissfully unaware, ffdshow has "frame type" as part of it's on screen display. Of course you've got to play the video and stop it on the frame in question.....
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Old 9th July 2012, 03:25   #4  |  Link
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You can also use ffdshow + DirectShowSource in AviSynth to get granular seeking.

I believe this method doesn't make a distinction between IDR pictures and I pictures, and simply calls them all I pictures.
These are all my personal statements, not those of my employer :)
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