5.1 audio down to 2.0

vectorizer wrote on 5/14/2011, 11:09 AM
My Panny TM300 camcorder records 5.1 audio with its built-in microphones. Using a project with 5.1 audio in SMS10HD works fine and renders as expected. But sometimes I just want a 2.0 (stereo) project, because I don't need the extra channels and making volume envelope edits is much easier.

Problem is that if I use a camcorder file with 5.1 audio in a 2.0 project, the R channel is much quieter than the L channel. From experiments, it *seems* like LF channel in the 5.1 file is going to the L channel of the project (as expected), but the C(enter) channel in the 5.1 file is going to the R channel of the project. Of course I could just boost the R channel, but that raises the noise floor.

I don't know if this is something messed up in the camcorder file (though I can only find one audio stream), or the way SMS is mapping or mixing the 5.1 down to 2.0. I can't seem to find a way to specify the channel mapping in SMS from 5.1 to 2.0, or even a way to mix down from 5.1 into 2.0. This seems like a pretty elemental function for software that supports both 5.1 and 2.0, so I almost expect I'm missing something obvious. (One other thing that's probably not relevant: when I use an external stereo microphone on the camcorder, it produces 2.0 files, and the L & R channels work as expected in SMS.)

Can anyone offer suggestions?

Comments

musicvid10 wrote on 5/14/2011, 12:30 PM
The stereo downmix button on the surround mixer isn't working for you?
Markk655 wrote on 5/14/2011, 1:41 PM
The good news...It is the way Panasonic reads the AVCHD files from at least some Panasonic camcorders. It appears in the trimmer that way too and Sony acknowledged the bug even back in VMS 8. I have used 5.1 rendering with my SD-1, and never tried to downmix.

At the worst, a workaround would be to render the 5.1 soundtrack to a stereo soundtrack and then use that in the audio timeline.
vectorizer wrote on 5/14/2011, 3:13 PM
@musicvid I don't see a stereo downmix button
musicvid10 wrote on 5/14/2011, 3:45 PM
Movie Studio doesn't have this? I'm surprised.

Markk655 wrote on 5/14/2011, 6:48 PM
Checked, no downmix button in VMS (I even looked in help and didn't find it there either).
knockatoone wrote on 5/18/2011, 12:10 PM
When I set up a project's proeperties I set audio to stereo . When I bring a AVCHD video to the time line with 5.1 audio I am asked if I want to change the project to 5.1 or stick with stereo. I choose stereo and VMS gives me good stereo audio - I see no difference in the L & R track other than they have different sounds as they should...
I may be missing something but VMS 10 HD Plat handles this for me ??
Markk655 wrote on 5/18/2011, 6:38 PM
I think that is because (at least according to your profile) you are using a Sony AVCHD cam. There is a bug in the AVCHD support for at least some Panasonic camcorders. The different manufactures use slightly different AVCHDs.
vectorizer wrote on 5/22/2011, 7:19 PM
@Markk655 Thanks for verifying that there is no downmix button in VMS, and for pointing out that Sony cams are OK but Panasonic (my cam) has a recognized problem bringing its 5.1 files into a stereo Vegas project.

I think found the solution, based on the hint about the (missing) downmix button on the Master mixer. First bring a 5.1 audio file into a 5.1 project. Then right-click on the mixer, click Audio Properites, get the Project Properties dialog with the Audio tab selected. Then, change the "Master buss mode" from "5.1 Surround" to "Stereo". This changes the mixer to a stereo Master, and all the audio tracks get a stereo Pan slider. Now I can just mix the 5.1 tracks I want into stereo, and mute or delete the unwanted tracks.

Not ideal, but beats having to go through a render step.