[FFmpeg-user] compand filter issues

[Moritz Barsnick]

Hi,
since nobody has tackled this issue yet:

On Tue, Apr 01, 2014 at 15:49:01 +0800, Darren Breeze wrote:

> /root/bin/ffmpeg -y -threads 0 -i /mnt/datastore/workflow/transcode/inbox/pop01/source_1080p.mp4 -aspect 16:9 -pix_fmt yuv420p -b:v 1800k -minrate 1800k -maxrate 1800k -bufsize 1835k -preset slow -x264opts keyint=33 -vcodec libx264 -acodec libfdk_aac -strict experimental -profile:v main -f mp4 -ac 2 -ab 192k -af compand=.3|.3:.8|.8:-90/-52|-52/-36|-36/-28|-20/-20:6:0:-20:0.8;volume=volume=-7.5dB /tmp/transcode/target_1080p.mp4
> 
> Whilst the processing works fine on channel 1 of the output file, channel 2 has high level to the point of clipping out.

The complete, uncut output from your ffmpeg command would help.
Possibly with the added argument "-loglevel debug".

My guess is that possibly your volume filter isn't being applied at
all. (The command output would show us, if that were the case.) I'm not
a total expert and may be mistaken here, but you are using ';' as a
separator:
> -af compand=.3|.3:.8|.8:-90/-52|-52/-36|-36/-28|-20/-20:6:0:-20:0.8;volume=volume=-7.5dB
but that is meant for separating filter chains, not filters. You
probably should be using ','. [*]

Moritz

[*] "Filters in the same linear chain are separated by commas, and
    distinct linear chains of filters are separated by semicolons."
    http://ffmpeg.org/ffmpeg-filters.html#Filtering-Introduction