VHS capture -> audio edit = pitch problems

[Maccara]

Hi,

I hope someone has encountered this before and could point me to correct direction where to look at.

Short description: Capturing ok, audio in synch, audio ok. Demux audio -> cleanup & convert to mono -> mp3 (lame) -> remux results in changed audio pitch (mp3 file itself is ok when listened separately). Straighforward encodes from DVD (with AutoGK) haven't had this issue.

Software used: VirtualVCR for capture (AVSync dynamic resampling on) codec = PICVideo MJPEG audio = PCM 44.1kHz 16bit stereo, avisynth for trimming/deinterlace, virtualdubmod 1.5.4.1, adobe audition 2.0 for audio edits.

Processing:

1st stage: Capture with VirtualVCR, Determine trims in vdubmod, prepare avisynth script with trims + deinterlace + crop, open avs in vdubmod and use neatvideo for cleaning up, save as avi (picvideo mjpeg again + PCM audio).

Up to this point everything is ok with audio. If I now put this through AutoGK (3.35b) it stays ok too.

2nd stage: Demux (or save stream to WAV - doesn't matter) audio with vdubmod, open in audition (convert to 32bit). In audition: convert to mono (mix 50% L/R - could also choose either channel, as this really is mono file to beging with), remove noise, pops, clicks etc, normalize, convert to 16bit, save. Convert to mp3 (lame -V6 --vbr-new). At this stage the mp3 plays fine in winamp. Remux avi with this mp3 in vdubmod (interleaving default, i.e. perload 500ms, interleave every 1 frame, no dealy, offset to maintain a/v sync, cut off audio when stream ends).

At this stage if I play the video file (in zoom player), the audio pitch is significantly higher (I mean, the guys sound almost like they've gone through mickey mouse conversion). I also notice, that zoomplayer shows as the "playing FPS" a fraction higher than the listed 25fps it should be (not over 26fps, though) and in the original avi it stays closer to the listed 25fps. Difference is so small I wouldn't expect to hear any difference, though.

I just did a remux with the filtered mono wav, and it also plays ok. So something is wrong when converting to mp3 or when muxing the mp3 file.

I'm now going to let AGK to encode the muxed avi with filtered wav to see if it results in a good/bad pitched avi with mp3...

If you have any suggestions, they're welcome.

[johnsonlam]

I may not able to solve your problem, but nice to discuss.

I use totally different approach, so I haven't experience anything, you're more experience than me cause I don't use AVISynth, it's good but a bit complex for me, and I didn't have any information to compare the plugin with Virtualdub, I did all the work with VDub.

I've met this many years before, but I hardly remember exactly the parameters I use, I just remember the different bit depth causing problem.

Did you try skip converting the WAV to 32bit and TRY direct convert 16bit stereo WAV to mono with Vdub? Please try the latest Vdub 1.6.16, it's working fine! Or just use Vdub-MPEG2 if deal with MPEG2.
(Since MPC let me capture video and audio in separate file, I don't need demux process, and I usually no need to remove noise, otherwise I use Adobe Auditon 1.0 without changing bit depth)

VirtualVCR won't work with my card, so I use Media Player Classic 6.4.8.5 (6.4.9.0 have bug!) with Mono since my city's TV don't have Stereo, I use HuffYUV to avoid any loss during capture, then de-interlace and cleanup noise in Vdub (also change to mono if I process video of someone else), finally encode with XviD 2-Pass.

**last minute note:

Are you using AVI container? As I know only MKV handle MP3 VBR correctly, AVI will causing outsync or maybe more problem, try using CBR instead.

[Maccara]

Thanks for the suggestions.

As I stated above, just muxing with the edited & filtered wav produced a perfectly working file, so in general the issue shouldn't be the audio editing itself (and 16bit->32bit->16bit conversion _definitely_ won't cause this kind of issue - done it hundreds of times in the past without problems).

I have now also tested what happend when that is converted with autogk to avi+mp3 - pitch gets screwed again.

So, something happens when converting my final 44.1kHz 16bit mono wav to mp3 and muxing it with the final avi.

I'll have to try with different formats to find out what exactly causes this, as I've never had any problems with "standard" audio of 44.1kHz stereo wav (edited or not) -> mp3 with adequate bitrates. And there's no problem with the original audio converted & muxed.

[johnsonlam]

Thanks for the suggestions.
I have now also tested what happend when that is converted with autogk to avi+mp3 - pitch gets screwed again.

So, something happens when converting my final 44.1kHz 16bit mono wav to mp3 and muxing it with the final avi.


Maybe AUTOGK have bugs, also make sure the MP3 is not VBR.


I'll have to try with different formats to find out what exactly causes this, as I've never had any problems with "standard" audio of 44.1kHz stereo wav (edited or not) -> mp3 with adequate bitrates. And there's no problem with the original audio converted & muxed.

I suggest you simplify your process, AUTOGK is simple but you have no idea what's going on inside, so I use Audition because I know exactly what's going on.

For simple operation, I stick to Vdub's audio conversion, it never fail.

Sorry can't really help, glad to have a nice discussion.

[Maccara]

Maybe AUTOGK have bugs, also make sure the MP3 is not VBR.
I'm actually just now trying CBR. Normally, VBR doesn't cause any issues, but it may be a factor in this (as this is a low bitrate mono-vbr). I'm now doing 64kbps cbr (due to the original quality of the audio this may be passable - have to listen to it) - I'll know in an hour or two how it works. ;)

I don't suspect a bug in AutoGK, as this happens also when I do it manually myself.
I suggest you simplify your process, AUTOGK is simple but you have no idea what's going on inside, so I use Audition because I know exactly what's going on.
Actually, I have a pretty good idea what happens inside AutoGK. ;) Besides, I _have_ done all of this manually too with the same results - actually my first suspicion was I did something incorrectly manually by accident. Doesn't seem to be so.
For simple operation, I stick to Vdub's audio conversion, it never fail.
I already know I can make it work with "normal" conversions - I'm not really interested in that at this point as I already know it works ok (for this movie too). Just trying to figure out what goes wrong when I'm "maximizing" quality vs bitrate.
Sorry can't really help, glad to have a nice discussion.
No problem. And actually you're helping me by giving some alternative ideas which I didn't come to think of (like vbr vs cbr, whereas vbr usually "works" nowadays it can of course cause issues in some cases due to avi container).

[Maccara]

Ok, the problem really was the VBR mp3 as you suggested.

With CBR everything is fine. And checking the audio quality, this edited & cleaned up low bitrate CBR version is still much better than the original audio directly used without cleanup, and uses "quite" a bit less space for audio. ;)

So, in the future I have to just remember not to use low bitrate mono vbr audio files and everything should be ok. ;)

Thanks for your help!

[johnsonlam]

Ok, the problem really was the VBR mp3 as you suggested.

With CBR everything is fine. And checking the audio quality, this edited & cleaned up low bitrate CBR version is still much better than the original audio directly used without cleanup, and uses "quite" a bit less space for audio. ;)

So, in the future I have to just remember not to use low bitrate mono vbr audio files and everything should be ok. ;)

Thanks for your help!

Glad to know you solved the problem :goodpost: