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Digitizing mono vinyl: using phase-inversion to reduce noise
alfienoakes101
post May 2 2007, 23:36
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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
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AndyH-ha
post May 9 2007, 23:38
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The overall advantage is in declicking first. However, "completely removed" vs "reduced to the point of inaudibility when listening with closed back headphones" might be debated from a philosophical viewpoint (i.e. what is acceptable or desirable? how do you actually tell?). Often, many clicks are gone as far as any practical consideration goes. In the case of large clicks that are only partially removed, they are often enough made easier to deal with. First converting to mono was always "first," never the end of the process. My earlier discussion deals with why I eventually abandoned that approach.

I appreciate the aesthetic viewpoint of trying for the ‘perfect' fix but in practical terms that is often irrelevant. One might sometimes, or often, say with reasonable confidence that the removal of a small click produces exactly what would have been recorded had the disk defect not existed, but in many cases it isn't possible to know unless one has another, undamaged, source against which to make a comparison (essentially never in my case). Besides, we are talking about recording from an LP. Do it twice, or ten times, and you get something slightly different each time.

I've done complete albums manually, with WaveRepair and with CoolEdit. I get the urge upon infrequent occasions when the LP condition is especially good (there will only be some thousands, or tens of thousands, of clicks to remove, instead of hundreds of thousands) and the music has quite a bit of ‘delicate' detail, but I'm am not sure that it actually makes a difference that is detectable to anyone who might listen to the result.

It is possible to noticeably, or badly, damage a recording with automated declicking, but it is usually possible to avoid that. In most cases I do several steps of automated declicking (and possibly decrackling), then I go through once or twice, or sometimes more, to find what the automated declicking couldn't handle. I always have the unprocessed copy available to copy over a bit that was damaged by automated declicking, but I don't need it for very many albums.

The results of automated declicking will never be exactly the same as manual declicking. It is easy to make comparisons and see the differences in an audio editor. Hearing the differences, however, is not easy, or not possible, given "good" automated declicking (except for the more serious problem here and there).

I've done A/B comparisons, and ABX comparisons a fair number of times when I was unsure or anxious (do a section manually, compare that result with the same section done automatically). Most of the time either I can't tell any difference or I can only tell a difference through a very close comparison. In the later case, a decision has to be made: put in ten extra hours (or 48 extra hours) to get something I will never again be able to detect (because I won't be doing A/B comparisons after I'm done and just want to listen to the music) or go with the "good enough" result.
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cliveb
post May 10 2007, 10:03
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QUOTE (AndyH-ha @ May 9 2007, 23:38) *
However, "completely removed" vs "reduced to the point of inaudibility when listening with closed back headphones" might be debated from a philosophical viewpoint (i.e. what is acceptable or desirable? how do you actually tell?). Often, many clicks are gone as far as any practical consideration goes. In the case of large clicks that are only partially removed, they are often enough made easier to deal with.

Andy, I think you and I are largely in agreement over many aspects of LP restoration. It was certainly not my intention to start a fight over this.

Of course, if some easy process produces as good an audible result as a more involved process, then the easier process should be used. There is no argument over that. I'm just surprised that you've found that mixdown to mono can actually reduce clicks sufficiently. In the case of damage to one groove wall only (ie. the glitch is only on one channel), then a preliminary mixdown to mono will result in that glitch appearing in both channels, but 3dB down. There are very few glitches which audibly disappear when they are reduced by only 3dB. I haven't done a huge number of mono records - most that I have were 78s - but I was very surprised by how many glitches were indeed almost entirely on one channel only.

QUOTE (AndyH-ha @ May 9 2007, 23:38) *
The results of automated declicking will never be exactly the same as manual declicking. It is easy to make comparisons and see the differences in an audio editor. Hearing the differences, however, is not easy, or not possible, given "good" automated declicking (except for the more serious problem here and there).

Agreed. And if automated declicking gives acceptable results, then it is of course easier to use it. My own experience is that automated declicking is usually worth doing, but a manual tidyup is nearly always necessary. Automatic declickers usually miss low level "ticks", and often make a dog's dinner of large clicks and pops. They are also pretty helpless when it comes to things like "scuffs" and "thuds".

But we're getting away from the subject of this thread, which was specifically about mono records. And in that respect I am completely with you on the desirability of recording and restoring mono records in stereo, prior to a final mixdown to mono.
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Posts in this topic
- alfienoakes101   Digitizing mono vinyl: using phase-inversion to reduce noise   May 2 2007, 23:36
- - bryant   When you mix the left and right channels to produc...   May 2 2007, 23:54
|- - alfienoakes101   QUOTE (bryant @ May 2 2007, 23:54) Your l...   May 3 2007, 01:16
- - AndyH-ha   There are two reasonable approaches. Which one to ...   May 3 2007, 00:25
|- - Wook   QUOTE (AndyH-ha @ May 2 2007, 23:25)...   May 3 2007, 10:05
- - pdq   The noise in the two channels can be highly correl...   May 3 2007, 12:19
|- - Wook   QUOTE (pdq @ May 3 2007, 11:19) The noise...   May 4 2007, 12:02
|- - pdq   QUOTE (Wook @ May 4 2007, 07:02) QUOTE (p...   May 4 2007, 16:51
- - Robbie   Certainly just summing the two channels will cance...   May 3 2007, 12:33
- - alfienoakes101   I guess then that the "noise" that I hav...   May 3 2007, 17:49
|- - bryant   QUOTE (alfienoakes101 @ May 3 2007, 09:49...   May 3 2007, 18:01
|- - pdq   QUOTE (bryant @ May 3 2007, 13:01) OT: Th...   May 3 2007, 20:05
|- - hushypushy   QUOTE (pdq @ May 3 2007, 12:05) QUOTE (br...   May 4 2007, 06:21
- - AndyH-ha   That cartridge alignment is (reasonably) correct h...   May 3 2007, 19:57
- - Axon   1. Sum and difference the L and R channels to get ...   May 4 2007, 06:46
- - AndyH-ha   1. Sum and difference the L and R channels to get ...   May 4 2007, 07:56
- - 2Bdecided   Back to removing noise from mono LPs: I've alw...   May 4 2007, 10:41
- - AndyH-ha   The best way to play a mono recording must be with...   May 4 2007, 19:45
- - 2Bdecided   I find... stereo > declick > decrackle ...   May 8 2007, 13:56
- - AndyH-ha   It's a trade-off. There is some advantage to m...   May 8 2007, 21:47
|- - cliveb   QUOTE (AndyH-ha @ May 8 2007, 21:47)...   May 9 2007, 08:40
- - AndyH-ha   The overall advantage is in declicking first. Howe...   May 9 2007, 23:38
|- - cliveb   QUOTE (AndyH-ha @ May 9 2007, 23:38)...   May 10 2007, 10:03
- - 2Bdecided   Rather than saying "it won't work", ...   May 10 2007, 10:36
|- - cliveb   QUOTE (2Bdecided @ May 10 2007, 10:36) My...   May 10 2007, 23:17
|- - cliveb   QUOTE (2Bdecided @ May 10 2007, 10:36) If...   May 11 2007, 09:51
|- - 2Bdecided   QUOTE (cliveb @ May 11 2007, 09:51) QUOTE...   May 14 2007, 10:34
|- - cliveb   QUOTE (2Bdecided @ May 14 2007, 10:34) Se...   May 14 2007, 12:30
- - AndyH-ha   Automated declicking is never the end of declickin...   May 10 2007, 19:58
- - AndyH-ha   I have a segment of that recording, declicked, tha...   May 11 2007, 05:44
|- - cliveb   QUOTE (AndyH-ha @ May 11 2007, 05:44...   May 11 2007, 08:48
|- - 2Bdecided   QUOTE (AndyH-ha @ May 11 2007, 05:44...   May 14 2007, 11:35
- - AndyH-ha   No, there is no such box. Does its existence depen...   May 11 2007, 19:35
|- - woody_woodward   QUOTE (AndyH-ha @ May 11 2007, 11:35...   May 11 2007, 21:50
|- - cliveb   QUOTE (woody_woodward @ May 11 2007, 21:5...   May 12 2007, 10:41
- - charliemcdo   Sorry to be off topic here, but I just wanted to a...   May 12 2007, 18:02
- - AndyH-ha   Obviously, the file attachment section is a privil...   May 12 2007, 19:19
|- - cliveb   QUOTE (AndyH-ha @ May 12 2007, 19:19...   May 12 2007, 22:51
- - AndyH-ha   And do you perchance remember a late night visit f...   May 13 2007, 05:20
- - 2Bdecided   I bet it's something to do with developers or ...   May 14 2007, 09:55
- - 2Bdecided   Hi Clive, I wasn't criticising or complaining...   May 14 2007, 13:21
|- - cliveb   QUOTE (2Bdecided @ May 14 2007, 13:21) I ...   May 14 2007, 14:50
- - AndyH-ha   The file, resampled to 16 bit, is at http://www.hy...   May 15 2007, 08:43
|- - 2Bdecided   QUOTE (AndyH-ha @ May 15 2007, 08:43...   May 18 2007, 10:04
- - AndyH-ha   Do you want something from another album to play w...   May 20 2007, 00:42


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