I sent a VHS tape in for professional capture and DVD conversion. I am now in the process of ripping and editing the footage. I noticed that if I demux the audio and video and then open the resulting .AC3 file in Audacity, there are apparently 6 channels/tracks of audio present. Given that the source material was a VHS home movie made in 2001, I know that there weren't 6 channels originally recorded. Weren't most camcorders of that era mono? Audacity reports each of the individual tracks to be: Mono, 48000 Hz, 16-bit PCM.
Looking at the different tracks in Audacity, it appears that 1 is the "main" track, and the others appear to be copies of the original attenuated to varying degrees. Was this done by the DVD creation program just to fit some standard template (I'm guessing 5.1 channel)?
Did the DVD capture/creation program literally just copy and paste attenuated versions of the single original audio track to create the others?
Also if I make any edits to this file in Audacity and export it back to a .AC3 file, I get this warning:
"Your tracks will be mixed down to a single mono channel in the exported file."
Is that going to cause any problems if I want to remux it with the original video?
Try StreamFab Downloader and download from Netflix, Amazon, Youtube! Or Try DVDFab and copy Blu-rays! or rip iTunes movies!
+ Reply to Thread
Results 1 to 17 of 17
Thread
-
-
Very interesting. I didn't think a DVD conversion shop would even bother trying to do that. I know that Hollywood sometimes fakes mono into AC3 5.1 because consumers are dumb enough to think it's "better" than the original track, but I'm surprised that they'd even try to do that in a conversion. I suppose there is some possibility that camcorders of that era could try to do stereo, but I'm just guessing. I wouldn't expect much separation even if they did it.
I think Audacity is basically telling you that it's not fooled by this quasi-6 channel sound nor does it play that game, so it's going to save everything as a mono file and avoid that foolishness. Will it cause any problems? Not at all. But do note that some home theatre setups may only play such a file out of the front center channel. I'm no Audacity expert, but if you can get it to save the file as 2 channel "stereo", even if it's just mono duplicated in both channels, that should play out of the front left and front right speakers in a home theater setup and you might find that more pleasing. It'll still be mono but it might sound more natural than just coming out of the front center speaker. Criterion does this with their DVDs and BluRays. -
You can get dual mono out of Audacity. Me, I'd make it dual mono before sending it to Audacity by decompressing to stereo WAV using BeSweet or Head3che. Then you can reencode back to AC3 using whatever you usually use. And that's only if you need a mono or stereo track to save space or something. As DB83 mentions, editing the audio and video separately can be a tricky proposition
-
Originally Posted by manono
-
No, of course not. Earlier you said, "I am now in the process of ripping and editing the footage" which might imply cutting out extraneous parts and the like. That's where doing that to the audio separately from the video might be difficult. And if it's only the audio on which you'll be working, I'd convert it to a stereo WAV file first and then import it into Audacity.
-
Here is the output from the .MPG file, which should be identical to the .VOB:
Code:Audio ID : 189 (0xBD)-128 (0x80) Format : AC-3 Format/Info : Audio Coding 3 Mode extension : CM (complete main) Format settings, Endianness : Big Muxing mode : DVD-Video Duration : 1h 16mn Bit rate mode : Constant Bit rate : 448 Kbps Channel(s) : 6 channels Channel positions : Front: L C R, Side: L R, LFE Sampling rate : 48.0 KHz Bit depth : 16 bits Compression mode : Lossy Delay relative to video : -161ms Stream size : 245 MiB (9%)
Code:Audio Format : AC-3 Format/Info : Audio Coding 3 Mode extension : CM (complete main) Format settings, Endianness : Big Duration : 1h 16mn Bit rate mode : Constant Bit rate : 448 Kbps Channel(s) : 6 channels Channel positions : Front: L C R, Side: L R, LFE Sampling rate : 48.0 KHz Bit depth : 16 bits Compression mode : Lossy Stream size : 245 MiB (100%)
Also I apologize for the vague "editing the footage" statement when all I really meant was filtering the audio and/or boosting the volume. -
-
-
I've been guilty of saying that kind of stuff in the past too, but now I have changed my thinking on this kind of response. Is it REALLY helpful to inexperienced members to point out this kind of "one in a million" possibility without any explanation that while this is POSSIBLE, it is NOT LIKELY to be the case at all? For all practical purposes, if someone is dealing with WAV, the odds are huge that it's PCM.
-
I find suspect any transfer service that automatically does 2ch stereo vhs to 5.1ch ac3. It should have been 2ch or 1ch, depending on the true layout of original tracks. That would also enabled better quality with given bitrate.
Be careful with the combination of those 2? Channels, as there could be some minute but important timing differences between them which could screw up the sound royally.
Scott
P.s. some vhs cams were hifi = stereo, some linear = mono. Depending on cam. What kind was yours?
If mono, use only one of those tracks and then dupe it to 2nd track for 2ch mono..
Curious, why did you go DVD to edit?Last edited by Cornucopia; 5th Mar 2014 at 18:16.
-
OK, this makes sense. After applying an amplification mod to the fake 5.1 audio in Audacity and saving it as a new file, the new file is a mono track when I open it in Audacity.
How does Audacity generate a mono track from a fake 5.1 track? Does it just take the loudest of the 6 available tracks, or does it average them all, or what?
Similar Threads
-
1080p60 8 audio channels HDMI capture card
By stereoactivo in forum CapturingReplies: 7Last Post: 6th Mar 2013, 03:24 -
Can an S-VHS Player and S-Video Output Cable Benefit Standard-VHS Capture?
By Avagadro1 in forum CapturingReplies: 34Last Post: 5th Dec 2012, 18:31 -
Demultiplexing of 4 video channels and 2 audio channels.
By jays_jays30 in forum Video ConversionReplies: 1Last Post: 9th Jul 2012, 09:29 -
Can TMPGEnc 4.7.7.307 XPress support output 5.1 Channels???
By JackyWang in forum DVD RippingReplies: 2Last Post: 17th Apr 2011, 22:37 -
capture DV - overdub audio - output mpeg 4 - ???
By pgo in forum Camcorders (DV/HDV/AVCHD/HD)Replies: 1Last Post: 14th Dec 2009, 04:28