[MEncoder-users] Separating each of the 6 channels of ac3 file into separate wav files

[belcampo]

socke wrote:
> L Lee schrieb:
>> I recently originated a thread about multiplexing, but now I have a related
>> question about DVD audio.
>>
>> I have developed a method to use MEncoder to transcode some HD h.264 files
>> to mpeg2. The picture looks really good and the audio sync is close, just
>> not quite close enough (for every 2 hours of video, the video component
>> comes out about a second shorter than the audio).
>>
>> I can increase the tempo of the audio file just enough that it correctly
>> syncs with the video by incorporating a process to demux, convert the audio,
>> a 6 channel (dolby 5.1) ac3 file, into a stereo wav file using a52dec,
>> change the tempo using SoX (the most recent version of which is quite
>> robust), convert back to ac3 with ffmpeg, then re-mux.
>>
>> The problem is that the method I just described gives me a stereo mix-down
>> of the audio when it is converted to wav, which is fine for most of the old
>> video I routinely convert, but now I have some stuff that's newer and I'd
>> like to preserve the 6 channels through the tempo change process.
>>
>> I'm looking for the simplest possible way to separate those 6 channels into
>> discrete files, perform the tempo change on each and then combine them again
>> into a single ac3 file containing all 6 channels.
>>
>> Can MPlayer's dumpaudio option or any other functions of MPlayer and
>> MEncoder perform any of the conversion parts of the operation?
>>
>> I tried using the pan option, then dumpaudio, but the command I used
>> resulted in a file that still contained all the channels, so it's clear that
>> I don't understand the processing steps I'm trying to use:
>>
>> mplayer -channels 1 -af pan=1:1:0:0:0:0:0 channel 0 audio.ac3 -dumpaudio
>> -dumpfile 1-channel.ac3
>>
>> Help will be appreciated. Thanks very much!
>>
>>   
> I recently did some ac3 speed change (for conversion between 24000/1001
> and 25 fps). I used the following pipe to do so:
> 
> ffmpeg -v 0 -i "$AUDIOFILE" -f sox - \
> | sox -S -V -p -p speed 1.04270833333333 \
> | ffmpeg -v 0 -i - -acodec ac3 -ab 448000 -y "$AUDIOFILE2"
> 
> 
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Whit what version of ffmpeg and sox does this work ? I tried several, 
but get errors like:
Unknown input or output format: sox
sox FAIL formats: can't open input  `-': premature EOF
pipe:: Unknown format