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Incorrect channel setup with AAC 6.1 audio

Posted: 10 Mar 2021 14:54
by CutterX
Hi!

I've transcoded a 6.1 audio track from WAV to AAC. When playing the WAV track with VLC, voices are heard normally. When playing the transcoded AAC track however, the voices from channel CF are completely absent and the channel setup sounds different.

My channel setup is stereo.

WAV and AAC formats use a different channel order:
Image

VLC reports a slightly different channel setup for each file:
  • WAV track: 3F2M1R/LFE
  • AAC track: 3F3R/LFE
VLC seems to use a different audio converter for each file:
WAV track (link to full log):
main debug: conversion: 'f32l'->'f32l' 48000 Hz->48000 Hz 3F2M1R/LFE->Stereo
main debug: looking for audio converter module matching "any": 8 candidates
main debug: using audio converter module "simple_channel_mixer"

AAC track (link to full log):
main debug: conversion: 'f32l'->'f32l' 48000 Hz->48000 Hz 3F3R/LFE->Stereo
main debug: looking for audio converter module matching "any": 8 candidates
main debug: using audio converter module "trivial"

Both sample files are linked below:
Thanks.

Re: Incorrect channel setup with AAC 6.1 audio

Posted: 11 Mar 2021 12:14
by Lotesdelere
You should create a new ticket on the VLC Trac with your above report, the links to your sample files and the link to this thread:
https://trac.videolan.org/vlc/

Re: Incorrect channel setup with AAC 6.1 audio

Posted: 12 Mar 2021 20:08
by CutterX
OK I did create a bug there: https://trac.videolan.org/vlc/ticket/25521