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

Beeblebrox zaphod at berentweb.com
Thu May 8 10:08:33 CEST 2014

Hi & thanks for the input guys...

It seems my previous description of the issue caused a misunderstanding:

* There is no constant background noise
* The noise appears when the speaker starts to talk - so "distortion" is
perhaps a more accurate term?
* I have noticed that high frequency sounds do not have much distortion
(when a woman with high pitched voice speaks)
* As opposed to some lower frequency sounds which are distorted to the
point they are incomprehensible (when a male with bass voice speaks)
* My first reaction in this case would be that the "compand" values need to
be played with. In the filters documentation (
https://www.ffmpeg.org/ffmpeg-filters.html#compand), it omits mentioning
what the colon ":" separator does. I also can not claim to have fully
understood the "x0/y0|x1/y1" business. Observing that the documentation
lists 7 compand parameters, and that in my example there are also 7 values
separated by colon, does this mean:
".3|.3:1|1" > attack : delay values for dual channel
"6" > soft-knee
"0" > gain
"-90" > volume
"0.2" > delay
* Unless I misunderstand, conflicting values for "volume=1.8 & volume= -90"
in this case would just be silly!
* gain=0 seems to be OK, since very little distortion is observed on the
high-frequency end.
* I have no idea what soft-knee=6 would be doing?
* As mentioned above, I (k)need (or is it knead?) help on what to make of
"-90/-60|-60/-40|..." part of this knob.

Thanks & Regards.

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