[FFmpeg-user] Frame types

Carl Eugen Hoyos cehoyos at ag.or.at
Sun Feb 3 22:58:59 CET 2013

Steven Penny <svnpenn <at> gmail.com> writes:

> It appears that
>   I-frame
>   intra frame
>   key frame

>   reference frame
> are synonymous 

Not exactly.
I-frames (intra frames) can be reference frames in 
all codecs that support non-key frames but they 
don't have to be reference frames.
It probably makes more sense to call I-frames 
key frames if they are actually used as reference 
P-frames and B-frames can also be reference frames 
in codecs that support this (at least h264).

> while "inter frame" is synonymous with "non I-frame" or
> "P-frame and B-frame".

Yes, those are the frames that need reference frames to 
be decoded (correctly).

Carl Eugen

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