[FFmpeg-user] ProRes422 with 8 audio tracks converted to mp4 -- muffles audio 4

Carl Eugen Hoyos ceffmpeg at gmail.com
Tue Nov 20 13:05:30 EET 2018

2018-11-20 4:28 GMT+01:00, Harvey Pikelberger <communque at gmail.com>:
> Testing the creation of 8-audio-channel mp4 proxies from ProRes422
> sources using ffmpeg. For some reason audio channel 4 of the mp4
> is coming back muffled, like it got drowned in a pool.

Every aac encoder will assume that one of eight input channels is the
lfe channel and will only encode low frequencies for this channel.
(Maybe not "every" but in any case, this is the issue you see.)

> Recently tested using DNxHD mxf files -- same audio configuration
> and everything worked perfectly.

That sounds very unlikely / command line and complete, uncut console
output missing.

Either use pcm (although I believe you will get a wrong channel
configuration which also may lead to issues) or split the audio input
into stereo or mono channels.

Carl Eugen

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