[Ffmpeg-devel] How are key-frames in Cinepak identified?

Mike Melanson mike
Thu Apr 27 01:58:29 CEST 2006

Harikrishnan Varma wrote:
> Hi,
>  I am debugging a "seeking to key-frame" bug in .mov files containing
> cinepak video. In lib/avcodec/cinepak.c, s->frame.key_frame is not
> updated to indicate a key-frame. Looking at
> http://www.csse.monash.edu.au/%7etimf/videocodec/cinepak.txt, is it
> correct to assume that if all strips in the frame have a strip id of
> 0x1000, it is a key-frame?

I don't think the key_frame field is especially reliable. Besides, the 
Cinepak decoding occurs at the video decoding level. Most multimedia 
players operate seeking based on keyframes as defined by the container 
format, QuickTime in your case. Check the QuickTime demuxer in your 
multimedia app. Make sure it is handling the stss atom correctly. If the 
app in question is ffplay, considering using a different app for general 
playback with proper seeking; ffplay is more a testbed than a general 
purpose multimedia player.

	-Mike Melanson

More information about the ffmpeg-devel mailing list