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

Steve Boyer steveboyer85 at gmail.com
Wed May 7 17:02:00 CEST 2014

On Wed, May 7, 2014 at 9:44 AM, Beeblebrox <zaphod at berentweb.com> wrote:
> Hi Steve, & Thanks.

Hi & you're welcome!

> I get an error: " Unable to find a suitable output format for
> 'compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2'
> compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2: Invalid
> argument"
> * What is the proper compand syntax?

It looks like you omitted a comma between the volume value and compand value:
ffmpeg -i video1.mpg -c:a libfdk_aac -af 'volume=1.8,
compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2' -c:v
libx264 -preset slow -crf 32 -f mp4 video1-out.mp4

I've not used ' or " in my filterchain before, so if the above command
doesn't work, try replacing the ' with ". Not sure if there's a
difference or not.

> * Do I need to make two runs (one for comapnd & audio only, second for -c:v
> libx264)?

If all of the audio filters and video filters (if needed) and settings
are complete and you are doing single pass CRF (as your command
looks), you should only need to run the command once, ever. I brought
up separating the video and audio while you are tweaking it, as your
command will encode the entire video every single time at the slow
preset. The time it takes for each iteration will add up in the long

> * What's the SoX fo ffmpeg translated compand values for example #2? I
> assume "/" is to replace the commas (,) do the colons replace whitespace?
> compand 0.1/0.3 -60/-60/-30/-15/-20/-12/-4/-8/-2/-7 -2 (or is it -7:-2?)

I will have to let someone else answer this question: I've never used
the compand filter in ffmpeg. Sorry!


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