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Hydrogenaudio Forum => General Audio => Topic started by: crazyman on 2005-01-06 17:47:58

Title: "Clean" audio wav editor in cutting/deleting
Post by: crazyman on 2005-01-06 17:47:58
Hi all,
I gave up of editing mp3 files using sophisticated graphic editors due to necessity of reencoding, and I started prefer rather mp3 trim which is simpler and much faster. But it does not have that many features and tools.
Those tracks that I have in wav format and need editing, before converting them into mp3 were edited using a wav editor. But even those quite good editors I have tested (AEDL, .....) f.i. in cutting/deleting very short parts, just like in case of mp3 implemented always quite strong glitch, and one cannot get rid of it even by further deleting again and again. In spectral view, I see a "chimney" created by cutting a piece (even in only several milliseconds cut). I thought there should be no problem and that operations like cutting/deleting should be clean without any extra implemented annoying sounds.
Any experience/advice is welcome.

Many thanks,

crzmn
Title: "Clean" audio wav editor in cutting/deleting
Post by: Kurt S on 2005-01-07 00:10:25
Interesting. could you provide a screenshot of the wave file and the glitch it's creating? Also what editor are you using?

One thing you might try first before editing the wave is make sure there is no DC offset. Any good wave editor will have an option to zero out any DC offset you may have.
Title: "Clean" audio wav editor in cutting/deleting
Post by: rutra80 on 2005-01-07 06:05:16
Probably the problem is that you don't cut at zeros (where waveform crosses the zero axis). When you cut at values reaching full peak, on playback start there will be a POP sound - speaker will suddenly "breath-in" or "breath-out" from its silent/zero/neutral position to the peak one. It's even worse when you do such a cutting in the middle of a song, where sample values at start & end of the deleted part don't match. Also, there may be a DC offset correction issue... Anyway, some editors have a "seek-closest-zero" command, IIRC in EAC's WAV Editor it's called Zero Crossing Adjustment.
Title: "Clean" audio wav editor in cutting/deleting
Post by: cliveb on 2005-01-07 08:36:35
Quote
But even those quite good editors I have tested (AEDL, .....) f.i. in cutting/deleting very short parts, just like in case of mp3 implemented always quite strong glitch, and one cannot get rid of it even by further deleting again and again. [a href="index.php?act=findpost&pid=263391"][{POST_SNAPBACK}][/a]

If you're cutting arbitrary bits out of a WAV file (or any audio file for that matter), then if the ends don't join up smoothly you will get a click. Even a discontinuity that lasts only one sample will be audible.

Trying to align at zero-crossing points (as others have suggested) can help, but there are two possible failure modes using this approach:
1. The zero crossing points may not match on the two channels, so you end up with a glitch one one channel.
2. There may not be a convenient zero-crossing point close to your desired edit.

In my experience, the only reliable solution is to be prepared to zoom right in on the waveform so you can see the discontinuity and manually fix it up. Some editors have the ability to redraw the waveform with the mouse; others have interpolation tools to smooth out the transition (and some have both).

If your situation is specifically one of cutting out "dead space" that is nominally silent, then the simplest approach would be to fade out/in to/from silence so that the section to be removed is genuine digital silence, then cut it out. That way you're guaranteed a glitch-free join.
Title: "Clean" audio wav editor in cutting/deleting
Post by: crazyman on 2005-01-08 18:59:49
Quote
Quote
But even those quite good editors I have tested (AEDL, .....) f.i. in cutting/deleting very short parts, just like in case of mp3 implemented always quite strong glitch, and one cannot get rid of it even by further deleting again and again. [a href="index.php?act=findpost&pid=263391"][{POST_SNAPBACK}][/a]

If you're cutting arbitrary bits out of a WAV file (or any audio file for that matter), then if the ends don't join up smoothly you will get a click. Even a discontinuity that lasts only one sample will be audible.

Trying to align at zero-crossing points (as others have suggested) can help, but there are two possible failure modes using this approach:
1. The zero crossing points may not match on the two channels, so you end up with a glitch one one channel.
2. There may not be a convenient zero-crossing point close to your desired edit.

In my experience, the only reliable solution is to be prepared to zoom right in on the waveform so you can see the discontinuity and manually fix it up. Some editors have the ability to redraw the waveform with the mouse; others have interpolation tools to smooth out the transition (and some have both).

If your situation is specifically one of cutting out "dead space" that is nominally silent, then the simplest approach would be to fade out/in to/from silence so that the section to be removed is genuine digital silence, then cut it out. That way you're guaranteed a glitch-free join.
[a href="index.php?act=findpost&pid=263534"][{POST_SNAPBACK}][/a]


Thanks for the explanation. Could you please recommend me a good and preferably free wav editor which can manually/automatically redraw the wave to match zero points, and which command to use then? Thx
Title: "Clean" audio wav editor in cutting/deleting
Post by: cliveb on 2005-01-09 12:03:07
Quote
Thanks for the explanation. Could you please recommend me a good and preferably free wav editor which can manually/automatically redraw the wave to match zero points, and which command to use then? Thx
[a href="index.php?act=findpost&pid=263829"][{POST_SNAPBACK}][/a]

If you manually redraw the waveform, you don't need to match zero-crossing points, just make sure the transition at the join is smooth. To do waveform redrawing, you need an audio editor that has a "pen" mode or some similar facility.

Audacity is the only genuinely free editor I know, and it has a pen mode to redraw waveforms. Plenty of other editors (including Goldwave, Adobe Audition, and my own program Wave Repair) will do what you want, but they're not free.
Title: "Clean" audio wav editor in cutting/deleting
Post by: rutra80 on 2005-01-09 12:27:00
In EAC's wave editor you can manually "drag the samples" too, just zoom in.
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