[FFmpeg-user] Slow conversion when using very low frame rates

[Carl Eugen Hoyos]

Tobias Rapp <t.rapp <at> noa-audio.com> writes:

> $ ffmpeg -i ffmpeg-huffyuv.avi -codec:v mjpeg -r 1:5 -an -y ffmpeg-test.avi

(Complete, uncut console output missing.)

Note that mjpeg is a very fast encoder while huffyuv 
is by definition (lossless archiving codec) not 
fast.

> the processing needs still around 80% of the original 
> processing time even though only about 1% of the frames 
> are passed through. It seems like FFmpeg is still 
> reading and decompressing each image before dropping 99% 
> of the frames.

The alternative is theoretically possible (for intra-only 
codecs which is not known from within ffmpeg.c) but not 
implemented.
Patch welcome!

Carl Eugen