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When playing 5.1 surround sound audio on stereo, the dialogues come out quiet low but the other sound effect comes out heavily loud. Fortunately, FFmpeg already has built-in filters to fix this issue like loudnorm and dynaudnorm but I have no clue how to use them with FFmpeg nor have I found any commands online that discuss these. I know that these FFmpeg filters work with MPV player which uses FFmpeg in real time.

I have used simple command like

 ffmpeg -i "movie.mkv" -acodec flac -ac 2 -vcodec copy "movie2.mkv"

which gives out an output files of smaller size and the overall volume is far lower than when played natively. This is not what I'm looking for, I want to mux all the channels into 2(stereo) without any cuts or loss in quality/bit-rate. I'm open to any other software/tool recommendation if FFmpeg lacks in achieving this.

Vin Raghav
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1 Answers1

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For the 5.1 to stereo downmix part of your question...

...this filter setup is based on an Avid Pro Tools default 5.1 to stereo downmix. I find this produces a superior sounding downmix to the default -ac 2 method.

-af 'pan=stereo|FL=1.0*FL+0.707*FC+0.707*SL+0.707*LFE|FR=1.0*FR+0.707*FC+0.707*SR+0.707*LFE'

This is equal to:

L 0dB, C -3dB, R 0dB, Ls -3dB, Rs -3dB, LFE -3dB

Or drop the LFE with 0.0*LFE

mwjb
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