Extract audio from multichannel .avi file... lots of problems.

Mug Funky · 7th April 2011, 02:00

here's a problem that i've been having a fair bit in recent times:

- we capture an avi of a feature film. it comes off a HDCAM-SR tape and thus has 8 channels of audio (well, up to 12).

- it's longer than 93:12.405, and hence the 8 16-bit channels add up to greater than 4 gigs.

- any and all methods of getting the sodding audio out of there reliably fail.

what i need is 6 mono tracks and 1 stereo (our ac3 encoder takes 6 monos, not 1 6ch wav).

i've tried:

- virtualdub will only read the audio length as being <film length> - 93:12.405, so a 100 min feature will show 6 minutes of audio, read from the start of the film.

- avs2wav (avs with avisource) has the same problem as VD, and returns only an 8 channel wav which means additional processing even if it did work.

- avs2wav (avs with qtinput, audio=2) will often deliver just silent audio

- soundout() delivers silent audio, and i can't run several instances at once, so delivering mono wavs would take ages and tie up the hard disk needlessly

- mainconcept appears to work, but i'd rather something i can automate.

- ffmpeg is useless, similar questions on the mailing list go ignored. it's amazing that such a useful program could work so viciously against itself that the man pages are incomplete, the CLI syntax is impenetrable and the mailing lists are full of obtuse "why would anyone want to do that" replies.

- ffmpeg piping into sox is showing promise, but i can't find the syntax to do it right.

- i've no idea if mencoder can even output multiple files at once. my google-fu is weak it seems.

- reaper (the DAW program) works, but only for short samples. it chokes hard on movies approaching a terabyte which we routinely use.

does anyone here have an idea? the rest of the internet has drawn a blank...

tebasuna51 · 7th April 2011, 11:28

Maybe you have 3 problems:

1) Decode the audio from a input.avi
I don't know the audio format.
If AviSource don't work maybe you can try FFAudioSource.

2) Downmix 8 channels to 6 or 2 channels
You can use AviSynth (samples in BeHappy)

3) Output monowavs
You can pipe to WavSplit (included in BeHappy)
Wavi input.avs - | WavSplit - prefix.wav -ignorelength

7th April 2011, 02:00	#1 \| Link
Mug Funky interlace this! Join Date: Jun 2003 Location: i'm in ur transfers, addin noise Posts: 4,555	Extract audio from multichannel .avi file... lots of problems. here's a problem that i've been having a fair bit in recent times: - we capture an avi of a feature film. it comes off a HDCAM-SR tape and thus has 8 channels of audio (well, up to 12). - it's longer than 93:12.405, and hence the 8 16-bit channels add up to greater than 4 gigs. - any and all methods of getting the sodding audio out of there reliably fail. what i need is 6 mono tracks and 1 stereo (our ac3 encoder takes 6 monos, not 1 6ch wav). i've tried: - virtualdub will only read the audio length as being <film length> - 93:12.405, so a 100 min feature will show 6 minutes of audio, read from the start of the film. - avs2wav (avs with avisource) has the same problem as VD, and returns only an 8 channel wav which means additional processing even if it did work. - avs2wav (avs with qtinput, audio=2) will often deliver just silent audio - soundout() delivers silent audio, and i can't run several instances at once, so delivering mono wavs would take ages and tie up the hard disk needlessly - mainconcept appears to work, but i'd rather something i can automate. - ffmpeg is useless, similar questions on the mailing list go ignored. it's amazing that such a useful program could work so viciously against itself that the man pages are incomplete, the CLI syntax is impenetrable and the mailing lists are full of obtuse "why would anyone want to do that" replies. - ffmpeg piping into sox is showing promise, but i can't find the syntax to do it right. - i've no idea if mencoder can even output multiple files at once. my google-fu is weak it seems. - reaper (the DAW program) works, but only for short samples. it chokes hard on movies approaching a terabyte which we routinely use. does anyone here have an idea? the rest of the internet has drawn a blank... __________________ sucking the life out of your videos since 2004

7th April 2011, 11:28	#2 \| Link
tebasuna51 Moderator Join Date: Feb 2005 Location: Spain Posts: 6,915	Maybe you have 3 problems: 1) Decode the audio from a input.avi I don't know the audio format. If AviSource don't work maybe you can try FFAudioSource. 2) Downmix 8 channels to 6 or 2 channels You can use AviSynth (samples in BeHappy) 3) Output monowavs You can pipe to WavSplit (included in BeHappy) Wavi input.avs - \| WavSplit - prefix.wav -ignorelength __________________ BeHappy, AviSynth audio transcoder.