[FFmpeg-devel] H264 keyframe detection not working

Lee Essen lee.essen
Sat Feb 7 18:59:54 CET 2009


I've just been working with some BBC HD content and have noticed that  
the keyframe detection isn't working.

The code seems to assume that you'll get a NAL_IDR_SLICE, but this  
media doesn't contain any!  I get slice types 9, 7, 8, 6, 1 on  
keyframe sequences then just 9, 6, 1 for everything else. So a  
keyframe is never detected despite them cleary being there if you  
examine the slice header for the slice type.

I've had a quick look at the standard and it does seem to imply there  
should be an idr slice, but it's just not there in the media!

Apologies if I'm missing something obvious I'm fairly new to this.



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