[FFmpeg-user] Keyframe

Mark Filipak markfilipak.windows+ffmpeg at gmail.com
Tue Apr 21 09:21:07 EEST 2020

Hey, Michael,

On 04/21/2020 01:55 AM, Michael Koch wrote:
> Am 21.04.2020 um 04:09 schrieb Mark Filipak:
>> Hey,
>> I have a question for you knowledgeable folks.
>> I've seen where some use the term "keyframe" but I've never seen a definition. It's not terribly 
>> important, but here goes...
>> I've assumed -- you know how good I am at that! -- that a keyframe is the I-frame that's at the 
>> beginning of a GOP.
>> Am I correct?
> I think this is correct, see also here:
> https://en.wikipedia.org/wiki/Key_frame
> Michael

That Wikipedia article implies pretty strongly that all I-frames are keyframes.

The MPEG spec uses the term "keyframe" occasionally, and in a manner that implies that keyframes are 
particular I-frames, but then doesn't really resolve the question regarding what quality makes an 
I-frame a keyframe. The only thing I could think of was the particular I-frame that begins a GOP. 
There's a problem with that: Not all stream formats have GOPs even though the literature about those 
formats refer to keyframes. Maybe in those formats, all I-frames are keyframes. ?????

I guess it's like "interlaced", just another video term that has a 'variable' definition. ;-)

Hopefully, someone else will contribute. For now, there's 2 votes for keyframe == 1st frame of GOP.

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