[FFmpeg-user] Extract all keyframes

Simon Thelen ffmpeg-user at c-14.de
Sat Jun 28 00:22:25 CEST 2014

On 27/06/14 at 11:37, Matthew Bondy wrote:
> My question: When I do not specify the frame rate I assume ffmpeg uses some
> default (20, 25?). The number of frames generated is in excess of the known
> number of keyframes by the ratio of 20/17 (or is it 25?, I cannot recall).
> When I use the option -r 17 (should I be more precise? '-r 17.1'?) I obtain
> a suitable number of frames but on the command line ffmpeg indicates the
> frame rate as it extracts the frames. This number fluctuates. Is the
> effective frame rate for keyframes a variable or is this a source of error
> in my analysis (I bring the images into software for material deformation
> analysis).
That's just the encoding fps. ie how many frames are being encoded every
second and has absolutely nothing to do with the fps of either the input
or the output file.

Simon Thelen

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