How to separate the left/right audio channel of MPEG2 file

[ckwok1]

I have MPEG2 files with audio in AC3. Recording of two different audio languages are stored in the left and right channels. Now, I want to create a DVD with 2 audio tracks from these MPEG2 files.

The ideal way is to extract the left and right audio channels directly from the MPEG2 file and save them separately into two mono AC3 files. Put the MPEG2 video file and the two AC3 file into a DVD authoring software (I am using DVD Workshop 2) and create the DVD.

The problems are:
1. Both video editing softwares (MPEG-VCR and Ulead Media Studio Pro 7) I have access to do not allow me to extract only the left or right audio channel.

2. In other words, I have to extract the audio to a stereo file and then try to separate them. But I don't have an audio editor that understands AC3 and this forces me to convert the audio to another format first. Conversion means extra time and extra distortion. I have hours of MPEG2 files in this format. I don't want to spend time waiting for conversion when there are better ways

Any one have suggestions for software or procedures to do what I want efficiently? Thank you in advance.

[Baldrick]

this is more audio realated. moving you.

have you tried sound forge? i think it supports ac3 audio.

[ropdoh]

You could try using besweet. If you use the -6ch option, it can split the ac3 into seperate channels (wav files), you can then encode the 2 you want to AC3 using besweet or some other program.

Since its commandline, you can probably automate the process with a script.

Alternatively, Goldwave can read in AC3 files if you have AC3Filter installed, although I don't think it can encode to AC3 so that might not help that much

[mats.hogberg]

Extract AC3 audio. Convert to wav, and save each channel as mono wav.
Load mono wav, double this to stereo, save wav and encode to ac3 with ffmpeggui. Repeat for 2nd channel.
Author.

/Mats

[ckwok1]

have you tried sound forge? i think it supports ac3 audio.

No, I have not tried sound forge. Even if it works, I don't want to spend several hundred dollar in order to separate the left/right audio channel only. Furthermore, most audio editor will implicitly decode the audio when the file is loaded, and encode again when the file is saved.

You could try using besweet. If you use the -6ch option, it can split the ac3 into seperate channels (wav files), you can then encode the 2 you want to AC3 using besweet or some other program.

Extract AC3 audio. Convert to wav, and save each channel as mono wav.
Load mono wav, double this to stereo, save wav and encode to ac3 with ffmpeggui. Repeat for 2nd channel.
Author.

/Mats

Decoding and re-encoding is something I am trying to avoid if possible.


Actually, I am just look for a simple program that can separate the left/right channel of a AC3 file, or a program than can duplicate the left channel to right channel and vice versa. No editing is necessary.

If such a program does not exist, may be I should write one. Can any one give me some information on AC3 and .mpa files? For example, the file structure or program source that can read and write to such audio files.

Should I post such request in the programming area instead of here?

[johns0]

Should I post such request in the programming area instead of here?

Yup.

[mats.hogberg]

Decoding and re-encoding is something I am trying to avoid if possible.

I doubt it's possible without wav (or other uncompressed shape) as intermediate step, wether "by hand" or hidden inside the workings of an application. It's like taking a zip file containing a 2 page Word document, trying to create 2 zip files with one Word document each, each Word document containing one page, without ever passing a Word document stage. Might be possible, but...

/Mats

[ckwok1]

Decoding and re-encoding is something I am trying to avoid if possible.

I doubt it's possible without wav (or other uncompressed shape) as intermediate step, wether "by hand" or hidden inside the workings of an application. It's like taking a zip file containing a 2 page Word document, trying to create 2 zip files with one Word document each, each Word document containing one page, without ever passing a Word document stage. Might be possible, but...

/Mats

I think it depends on whether "rematrixed" method is used or not. Since the audio of the left/right channel are completely independent, "rematrixed" should not be used. But it all depends on the encoder. And I have to admitted that the chance may not be good