Distortion in sound

[diwan]

Hi there,
I'm using the Sony PC9 camcorder, capturing my video using DVMotion, converting my video to SVCD format using tmpgenc, and burning using nero. A few days ago, I posted a problem that while the picture looks great on the SVCD (when I play it in my dvd player), the sound appears to have some high-frequency distortion (kind of like whistling particularly when a subject speaks). I have some more information that may help you diagnose my problem.
When I play the avi file and the mpeg2 files on my computer, I'm pretty sure (90%) I can hear the distortion on the mpeg2 files but not on the avi file (the reason for my uncertainity is that my dvd player is hooked up to a nice stereo system and thus any problems with the sound are much more obvious when I play the svcd on my dvd player).
When I looked at the avi file using VirtualDub it says that the sampling rate for the audio stream is 32000 and the Sample precision is 16-bit. In tmpgenc, the sampling frequency is at 44100 and it does not allow me to change it to 32000. Could this be the reason for the distortion? Any help in fixing/diagnosing this problem would be very much apprecaited.
I'm using the standard settings for TMPgenc to do my conversion (i.e., using NTSC under SVCD) and taking all the other defaults.

[Tommyknocker]

It could be the recording volume is set too high. Load the original video into Gold Wave and see if the amplitude is off the charted audio. If it is, you can use the noise reduction filter to lower it, then save it, and mux it with the original video with TMPGEnc to your VCD template.

[House de Kris]

Recording level is probably OK because the original AVI sounds OK. But, this reeks of the infamous TMPGEnc sample rate conversion blunder. Strip out the audio, convert it with any other software that is competent at sample rate conversion, and merge the audio back in with TMPGEnc. Simple isn't it? Well, at least that is what everyone else on this forum insists.

[diwan]

Thanks for the tip. I looked at the sound levels through GoldWave and it appears that the sound levels for the avi file (which does not distort when playing) and the mpeg1 file (which does distort) look nearly identical, both peaking at just a bit under 1.0 (decibels, I assume?). If they are looking identical (at least at the 1:100 zoom) then why would one distort and the other not? Is 1.0 too high? SHould I try to lower the level?

[diwan]

Regarding House de Kris's message:
I've also tried to use the toolame (sp?) as the external tool with tmpgenc and that leads to the same distortion. Would using this tool have a similar effect to what you are suggesting? If not, can you point me to instructions on how to go about doing what you are suggesting?
[/quote]

[Tommyknocker]

Perhaps you should use Virtual Dub to capture if it is possible. Use 44100 Hz audio. Since the audio will be the same in both programs, it should not cause any distortion.

[House de Kris]

Well, he's not necessarily capturing, he is transfering a DV file from his Sony camera to his computer. In which case, he is stuck with the audio sample rate used when recording.

I seem to recall that toolame was supposed to be able to do a decent sample rate conversion. Then again, I think it was converting from 48kHz to 44.1kHz that is supposed to be OK. Perhaps 32kHz to 44.1kHz has problems as well. If I recall correctly, there is another program like GoldWave (or some such) that may be able to do this.

Hopefully someone will be able to give you definitive instructions here.

[diwan]

Thanks to all the feedback, I was able to fix the problem. As was suggested, the problem was most likely with Tmpgenc's sampling rate conversion for audio. So I passed all my files through DVgate assemble and used it to change the sampling rate to 44.1k. Then I converted the files using tmpgenc and burned. The result was good sound and picture!
I think I've also discovered the source of my problem: my camcorder was set to record sound at 12 bits and not 16 bits. I've changed it to 16 bits now. Hopefully this means next time around I will not have to go through the extra DVgate assemble step.