Convert AC3 to WAV

Marel · 05-01-2007, 07:29 AM

Hi, I want to convert 6-channel audio file in AC3 compression to ogg. Since oggenc doesn't support AC3 input, I am trying first decompress it to PCM (wav).

Is there some program for Linux that can do this? It should also downsample it to 2 channels.

Emerson · 05-01-2007, 08:38 AM

You want ac3dec.

Marel · 05-01-2007, 08:58 AM

I'm not sure about it. I tried it, but it only plays the sound, didn't find a way to save it into file. Furthermore, in its man page, it says only supports 4 or 6 channels, and I need two. Third, even if I find a way it saves it into file, will it be wav, or raw pcm stream? It looks to me it would be the second.

Emerson · 05-01-2007, 09:22 AM

Oggenc takes raw stream as input, you can just pipe the output of ac3dec to oggenc.
MPlayer is another option, it can certainly handle AC3.
Also, Avidemux2 (it's an excellent multimedia tool BTW) can do it for you.

Marel · 05-01-2007, 09:52 AM

Quote:

Originally Posted by Emerson

Oggenc takes raw stream as input, you can just pipe the output of ac3dec to oggenc.

I tried

ac3dec stream.ac3 | oggenc -R 48000 -o newstream.ogg -

but ac3dec starts playing the sound trough sound card and resulting ogg file is empty.

Then I tried

Code:

mr@main:~/video$ ac3dec -D newstream.raw stream.ac3
5.1 Mode 48.0 KHz 448 kbps Complete Main Audio Service
Using PCM device 'newstream.raw'
ALSA lib pcm.c:2143:(snd_pcm_open_noupdate) Unknown PCM newstream.raw
snd_pcm_open: No such file or directory
Output open failed

and as You can see it doesn't work.

Quote:

MPlayer is another option, it can certainly handle AC3.

It can play it, but not what I need. If You have concrete command line options for this, I would be gratefull to see them.

Quote:

Also, Avidemux2 (it's an excellent multimedia tool BTW) can do it for you.

I didn't try to much Avidemux, so I'll try what can be done.

Marel · 05-01-2007, 10:39 AM

I managed to get wav file with avidemux by selecting "Wav PCM" Audio and chosing Audio/Save from menu.

However, it doesn't output ogg-vorbis correctly. It looks like there is really much problems with embeding vorbis at the moment. In addition to what I already said, Avidemux crashed while I tried to make it output vorbis sound with video in avi file, both with stream copy and libavcodec recompression.

sfaz32 · 05-01-2007, 01:22 PM

To Marel,

You can use mplayer and pipe its output to oggenc using the following script :

Code:

#!/bin/bash
INPUT="inputfile.ac3"
OUTPUT="outputfile.ogg"
mkfifo audiodump.wav
mplayer "$INPUT" -vc dummy -vo null -ao pcm:file="audiodump.wav" -channels 2 \
  & oggenc -q 9 "audiodump.wav" -o "$OUTPUT"
rm audiodump.wav

Replace inputfile.ac3 with your source. You can also use any file that mplayer can play.

Then replace "outputfile.ogg" to whatever you want.

Marel · 05-01-2007, 03:54 PM

Thank You. This way to use named pipes will be very usefull, I hope.