Hello - I know questions like these are asked a lot, but I have a slightly tricky issue.
I have about 30 video+audio files that have been captured incorrectly. They are mp4 H.264 with stereo AAC audio.
The video is fine and I don't want to re-encode that. The stereo audio is about -20db on the right leg.
What would be syntax of a windows FFmpeg command be to copy the video and left stereo audio leg and add 20db gain to the right leg only to a new file?
Any guidance much appreciated.
Thanks all - Duncan.
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for %%a in (*.mp4) do ffmpeg -i %%a -c:v copy -af dynaudnorm=n=0 "output\%%~na.mp4"
That should normalize the channels independently (to same level). If you want to do a "stupid" gain you probably have to split the channels and then do the "normal" gain or normalization filter.
Are they "real" stereo files? If they are not I would just convert to mono, or stereo but just by duplicating the left channel.
**really helpful** thanks you. For my purposes this approach worked just great.
For anyone in a similar situation, I had to make one tiny adjustment to increase the gain range to 20db
ffmpeg -i %%a -c:v copy -af dynaudnorm=n=0:m=20.0 "output\%%~na.mp4"
Your expertise is much appreciated.