Or you can use the matrix mixer in AC3filter. ./ffmpeg -i Safari DolbyDigitalPlus.m2ts -map 0:0 -vcodec copy -map 0:1 -acodec alacat Safari DolbyDigitalPlusOut.mkv ffmpeg 5.0. Instead of using FFMPEG to make a file, mpv supports FFMPEG filters. ffmpeg -i stereo.wav -map 0:0 -map 0:0 -mapchannel 0.0.0:0.0 -mapchannel 0.0.1:0.1 -y out.ogg Note that currently each output stream can only contain channels from a single input stream you can’t for example use '-mapchannel' to pick multiple input audio channels contained in different streams (from the same or different files) and merge. Alternatively, you can use the compromise coefficient of 0.6 The positioning is not preserved, but the volume for the side will be correct regardless if you do successive downmixing 71>51>20. You can now see why Traditionally, Side is just mixed 100% into back. But if you did 0.5, it will sound correct. For example, if you have a 5.1 source and want a stereo audio stream by dropping the extra.
When you then downmix this to stereo, the side will sound too loud since 0.7+0.7=1.4. ffmpeg -i in.mov -filter channelmapmapDL-FLDR-FR out.wav. It looks wrong, but sounds correct in 5.1. The correct coefficients for equal power, is 0.7*side into front & back. However, the perceived volume will be reduced by 3dB since 1 mono source is played into 2 speakers. If you want to do this, you might typically go 0.5*side into front & back so that 0.5+0.5=1. "But I want preserve the volume balance between front and surround channels,"ĭo you mean preserve the positioning between front/side/back? Traditionally, Side is just mixed 100% into back for 71>51.
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