[FFmpeg-user] mpeg2 filesize reduction: reduce video, enhance audio, codec selection

Beeblebrox zaphod at berentweb.com
Wed May 7 15:57:06 CEST 2014

@ Carl:
>> libfdk is the recommended aac encoder.

Thanks for the answer, it helped quite a bit.

I tried a run with -crf 28 on a 3 GB video file, and was not happy with the
size reduction (just 15% appx.). So I decided to bump the crf to 32 and
made a test run - the 3.1G file came down to 262M. The visual quality is
within acceptable limits considering the amount in size reduction.
($ ffmpeg -i video1.mpg -c:a libfdk_aac -af 'volume=1.5' -c:v libx264
-preset slow -crf 32 -f mp4 video1-out.mp4)

The problem is still the sound, however; it's human speech and the volume
of the speaker fluctuates - sometimes it's very hushed, other times (when
excited) it's very loud. volume=1.5 is a little low, so I may bump that up
to 1.8 or so, but I need a method to "normalize to median" or "set all
frames to xyz dB" the volume on the video (raise the hushed voice, diminish
or keep same the loud parts).
Any ideas on how that can be achieved?

Thanks and Regards.

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