how to judge the key frame in h264 stream

[alexsmith]

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]

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]

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]

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.