[nzlug] FFMpeg Help (Convert MonoLeft-Stereo to real Mono or mirrored Stereo)

[Joel van Velden]

On Wed, 2006-09-27 at 10:47 +1200, Andrew Bruce wrote:
> I've got a bunch of video files that have been recorded in some wierd Mono-Stereo configuration (ie Stereo with left channel containing audio, right channel as empty).
> 
> I'm trying to compress these files using FFMpeg as they are currently absolutely massive.
> 
> What I want to do is either downmix the whole thing to proper single channel only mono, or (better) take the left channel mono recording and put it across so that it is mono on both left and right stereo channels.
> 
> Has anyone done this, or know how it can be done?
> 
> I want to be able to do it within FFMpeg itself if possible, the actual issue is slightly larger than explained so I can't split the audio from the video at this stage (although if I have to, I'm happy to compress the video, split off the audio, modify it and re-add it to the video if I have to (or any other similar methods to this)).
> 
> Andrew


I'd suggest looking into mencoder. It uses ffmpeg internally so support
everything that ffmpeg does.

Mencoder/mplayer has a complex audio filters, one of which is re-routing
of sound channels. mencoder -af help should give you some examples.

eg mencoder -af channels=2:2:0:1:1:0 <plus other commands> would swap
left and right stereo channels for example.

eg mencoder -af channels=2:2:0:0:0:1 would duplicate channel 0 to both
left and right outputs.

As always the online help is best 
http://www.mplayerhq.hu/DOCS/HTML/en/advaudio.html#advaudio-channels

Cheers
Joel van Velden

> 
> 
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