Digitizing mono vinyl: using phase-inversion to reduce noise Options

[alfienoakes101]

Hi.

I have been using a long-winded process to reduce some extraneous noise when digitizing mono vinyl sources. With Sound Forge, I have been subtracting the difference between the two channels of my records, on the assumption that most of it is noise, and the resultant files are usually audibly better.

1. Invert the phase of one of the two channels on the original .wav file (1.wav).
2. Convert to mono by mixing the channels.
3. Save the difference (noise file) as a mono .wav file (2.wav).
4. Re-open the original "stereo" file (1.wav).
5. Convert to mono by mixing the two channels.
6. Save the sum as a mono .wav file (3.wav).
7. Open original "stereo" file (1.wav).
8. Open difference (noise) file (2.wav), copy it and overwrite onto left channel of 1.wav.
9. *edit* Invert noise channel.
10. Open sum file (3.wav), copy it and overwrite onto right channel of 1.wav.
11. Convert to mono by mixing the two channels.
12. Save changes to 1.wav.

Is there an audio editor that will allow me to subtract the difference of a stereo file in a single step, as it would save me a lot of time, and allow me to hear instantly whether the audio is significantly improved, without having to get confused by extra files? If I could work in flac, that would be even better.

If found the link below that references and old version of Cool Edit, but I gather that's been discontinued.

http://www.hydrogenaudio.org/forums/index....mp;#entry344060

Thanks.

This post has been edited by alfienoakes101: May 3 2007, 00:38

[2Bdecided]

Back to removing noise from mono LPs: I've always wondered if something like the "intelligent" vocal cut algorithms could be used in reverse to do a better job than simple summation?

With vocal cut, if something is on the L channel and the R channel in roughly equal amounts, then you want to remove it, and keep the rest.

With mono LPs, if something is on the L channel and the R channel in roughly equal amounts, then you want to keep it, and remove the rest.


The intelligent vocal cut algorithms FFT the audio (or similar) and analyse it to remove the common information, while keeping both stereo channels reasonably intact. It works nearly OK - you can easily introduce the kind of warbly mess that arises by chopping things around in the FFT frequency domain, but you can avoid it with some care.


I wonder if you could apply this principle to mono records? The simple summing only reduces the unwanted stuff by 6dB relative to the wanted signal. The FFT method would work better than that. I suspect the problem is that most unwanted stuff is broadband (and often impulsive in nature), and so not very responsive to frequency analysis.


If you have foobar2k, you can try this...

http://www.hydrogenaudio.org/forums/index....showtopic=46611

Cheers,
David.

This post has been edited by 2Bdecided: May 4 2007, 10:42