Vegas and 12bit/32KHz Audio

farss wrote on 6/20/2005, 8:30 PM
If we capture a tape recorded with 12/32K audio using Vidcap and drop it onto the Vegas T/L, Vegas reports the media properties as 16/32K.
If we drop a 12/32K AVI captured by a different app onto the Vegas T/L Vegas wants to build a proxy file.
It would seem that 12/32K DV audio uses non linear quantization so there's sure some room for it to be handled incorrectly.
Thing is I cannot find any reference to how such audio is handled in the Vegas documentation, obviously Vegas must have some smarts to build a proxy file. My guess is that Vegas and VidCap are doing the right thing but it's hard to be 100% certain when there's no mention of it anywhere and it's not exactly the easier thing to test either.
Not that I'd ever intentionaly run a camera/VCR at 12/32K but clients can and do all kinds of wierd things, we need to know for sure that we're handling their material correctly.
Bob.

Comments

farss wrote on 6/27/2005, 3:13 PM
Shameless bump,
surely someone from Sony can illuminate us on this, I'd of thought knowing how our audio is being handled would be of interest to everyone here.
Bob.
Chienworks wrote on 6/27/2005, 3:47 PM
Just a guess, but is it possible that VidCap is filling out the other 4 null bits to make 16 bit samples as it captures? Except for using up a bit more disk space there really isn't any reason not to do this, and it makes subsequent processing more efficient. The other capture software may be leaving the 12 bits alone and Vegas has to proxy them to process them.
John_Cline wrote on 6/27/2005, 4:03 PM
Actually, there IS a very good reason why not to simply fill the lower 4 bits with null bits. 12-bit DV audio uses dynamic range compression using a lookup table on encoding and decoding. If Vegas isn't doing the proper decoding, then the decoded audio is incorrect, plain and simple.

Refer to my post near the bottom of this thread:

http://www.sonymediasoftware.com/forums/ShowMessage.asp?ForumID=4&MessageID=398341

John
John_Cline wrote on 6/27/2005, 7:55 PM
Hmmm, I was just thinking that one possible reason that Sony hasn't responded to this thread is that they aren't processing 12-bit audio correctly and simply don't want to admit it. For me, it completely academic since I never use 12-bit audio anyway, but a lot of people do (usually because they haven't changed the default audio recording mode on their camcorder.)

John
farss wrote on 6/28/2005, 1:28 AM
John,
I suspect you might indeed be correct and if so that's a pretty sad state of affairs, I don't care so much that they're doing it wrong but at least we should be warned. As I said I don't go near 12/32K audio myself but it's hard to control what clients do.
Bob.
Avanti wrote on 6/28/2005, 11:52 AM
FYI, on a recent project, a client gave me some MiniDV shot in 12/32.
It played out of sync on the timeline of my project which was 16/48, but it rendered out OK.
ForumAdmin wrote on 7/8/2005, 2:32 PM
We expend most of our dev and QA efforts on 16/48 DV audio but we realize that sometimes people shoot 12/32 and we want to handle this as well as we can given the inherent limits.

If one of you would be able to post a set of downloadable raw (unrendered) files that clearly, audibly demonstrates a problem with the way we are handling 12/32 DV audio (for instance the "pulsing" that was reported to be present in Vegas but not in other apps- that would be a real problem) we'd like to evaluate those files and will post back here with an explanation, admission of error, workaround (tbd).