[FFmpeg-user] compand filter issues

[Darren Breeze]

Hi

I am trying to use the compand filter to compress audio on some files 
using the following build

ffmpeg version git-2014-02-10-03911c4 Copyright (c) 2000-2014 the FFmpeg 
developers
   built on Feb 10 2014 14:12:24 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
   configuration: --prefix=/root/ffmpeg_build 
--extra-cflags=-I/root/ffmpeg_build/include 
--extra-ldflags=-L/root/ffmpeg_build/lib --bindir=/root/bin 
--extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac 
--enable-libmp3lame --enable-libopus --enable-libtheora 
--enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree 
--enable-libfreetype
   libavutil      52. 63.101 / 52. 63.101
   libavcodec     55. 50.100 / 55. 50.100
   libavformat    55. 31.100 / 55. 31.100
   libavdevice    55.  8.100 / 55.  8.100
   libavfilter     4.  1.102 /  4.  1.102
   libswscale      2.  5.101 /  2.  5.101
   libswresample   0. 17.104 /  0. 17.104
   libpostproc    52.  3.100 / 52.  3.100

with the following command line


/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.

I have set up this to a WAV file output with the same results.

the source files have one audio stream of 2 channels

The volume filter is applying an overall level correction based on a previous loudness analysis, the issue remains if this is omitted from the filter.

Not sure what's going on

Darren Breeze