How to strip extra tracks from ac3

[Gorr]

Hello,
As I can play only stereo sound, I don't need to have 5 channel ac3 files. Can I remove extra i don't need to keep file size at minimum?

Thanks

[MaTTeR]

Of course you can! Select Dolby Pro Logic 2.0 soundtrack from within SmartRipper's stream processing tab and turn all the others off you don't need.

This is discussed in the ripping guides and I'm quite sure this very question has been posted somewhere on the board before.:devil: Read and search the forums a little before posting.

[Gorr]

Hi MaTTeR,
Thank you for the help.

>Of course you can! Select Dolby Pro Logic 2.0 soundtrack from within >SmartRipper's stream processing tab and turn all the others off you >don't need.

I'm afraid I didn't make myself clear enough.
The track I need is for dvd reauthering process known as ifo&cce.
I do not have Dolby Pro Logic 2 or whatever stereo tracks available on my dvd. AC3 5.1 DRC tracks are all I have.

AC3 contains 6 channels right?
What I need is to remove 4 channels without transcoding process which could result quality loss penalty.
As I need the new sound track to also contain timecodes as the original, it has to be AC3 not Pro Logic which do not support timecodes. Correct me at this point please.

I wonder how to determing which channels to keep and which ones to remove?

So the whole issue gets pretty questionable. This is why most ppl don't change sound tracks.

The reason I wanna do this coz I can only play stereo. And do not have too much space on my HD for storing my projects (i do not burn them).

Thanks

[Acaila]

I think you need to re-encode your AC3 file for this. Decode the 6 channels to 6 WAV's, then take the 2 you want and encode them into a new AC3. I don't know if there's anything that can do it directly.

[Gorr]

Thanks for the input Acaila.
I'm afraid this way I'll lose timecodes.

[MaTTeR]

Acaila is correct, you would nee to re-encode the audio with something like SoftEncode.

I doubt discarding a few of the channels would work, for one thing you couldn't get rid of the center channel or you would lose all dialog. I would think you need to keep both left and right channels as well. Perhaps a software product like SoftEncode would allow you to take a 5.1 AC3 file and downmix to a 2/0 DPL. I've never attempted this myself though.

[DmitryR]

You need to open the 5.1 version with SoftEncode choosing "decode to PCM" option in open dialogue and set 2/0 channel option in encode settings. That is so simple.

Or downmix the source 5.1 to 2 channel stereo with azid and the encode this stereo with SoftEncode.

Discarding channels will give you incomplete soundtrack.

[Gorr]

Great!
I agree discarding channels is not a good idea. Downmixing seems to be more logical to me.

Don't however know what should be the command parameters for azid1 (besweet) to downmix ac3 to stereo wav. I tried stereo surround in output modes, but looks like it simply takes L and R channels.

Thanks

[DSPguru]

stereo is L&R, surround is surround ;).