[FFmpeg-user] Invalid duration specification for force_key_frames

Moritz Barsnick barsnick at gmx.net
Thu Sep 3 10:54:22 CEST 2015

Hi Frans,

On Thu, Sep 03, 2015 at 10:36:32 +0200, Frans Gouverne wrote:
> since I recompiled ffmpeg some months ago, I cannot use expressions on the
> command line anymore, they are simply not recognized. For example:
> ffmpeg -re -i demo.mp4 -ac 2 -b:a 64k -ar 44100 -c:v libx264 -r
> exp:gt(25,30) -f mp4 output.mp4
> Invalid framerate value: exp:gt(25,30)

a) I can successfully use expressions for "-r" if I omit the "exp:"
   part. (That may have changed over the months, I don't know.)

b) gt(25,30) won't work with "-r", as "-r" doesn't accept "0"!
   From the docs:
   ‘gt(x, y)’
       Return 1 if x is greater than y, 0 otherwise.
   Are you looking for "max(25,30)"?

>   built on Jan 19 2013 20:36:06 with gcc 4.7.2 (GCC)

Did you say "some months ago"?? 32 months! How old was the ffmpeg you
were using before?


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