how to judge the key frame in h264 stream

alexsmith · 4th July 2012, 02:55

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
problem?

thanks in advance,
alex

Dust Signs · 4th July 2012, 07:05

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.

Dust Signs

hello_hello · 4th July 2012, 08:03

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.....

Blue_MiSfit · 9th July 2012, 03:25

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.

4th July 2012, 02:55	#1 \| Link
alexsmith Registered User Join Date: Apr 2012 Posts: 8	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 problem? thanks in advance, alex

4th July 2012, 07:05	#2 \| Link
Dust Signs Registered User Join Date: Jun 2004 Location: Salzburg, Austria Posts: 219	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. Dust Signs __________________ The number you dialed is imaginary. Please turn your phone by 90° and try again

9th July 2012, 03:25	#4 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	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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4th July 2012, 08:03	#3 \| Link
hello_hello Registered User Join Date: Mar 2011 Posts: 4,829	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.....