[FFmpeg-user] frame extract is not accurate enough

[Moritz Barsnick]

On Fri, Jul 24, 2015 at 09:15:16 +0000, Gergely Lukácsy wrote:

Apart from everything else:

> The strange thing that the total number of frames (300) produced is bigger than what the video duration (496 s) and the 1 sec framerate would indicate.

Smaller, you meant to say? Actually, you mistyped 496?

[...]
>   Duration: 00:04:56.92, start: 0.000000, bitrate: 1480 kb/s

The file you're showing us is 296.92 seconds long, not 496. Perhaps
that's according to the header, and the actual video stream is longer,
resulting in about 300 seconds. You would know better by letting ffmpeg
parse the complete stream:
$ ffmpeg -i /tmp/presentation.mp4 -f null -
or using ffprobe to count the frames.

Are you sure the video is truly CFR? Is it captured from some device
which delivers slightly varying frame rate?

Moritz