Subject:Showing my ignorance!

Posted by: Hummingbird

Date:3/14/2003 5:50:20 PM

I guess many of us like to think we are sound "experts" because we are the "sound people" in our own domains. I am going to have to humble myself and admit that I don't know as much as I would like to think I do! The problem is not some tricky file, but a genuine ignorance of not being able to see what I hear.

I have two recordings of live performances of the same work available to me; each separated by an hour, or so. One has a glitch at the end - the other doesn't. The one with the glitch is, overall, the better performance of the two. I pasted the good ending from the 'inferior' file to the other. There is an audible click - ever be it so slight! I can hear it, but no matter how much I magnify the waveform, I can't see it (or identify it from the surrounding waveform).

I suppose that if I fiddle around with placing the insert enough times, I might get lucky and eliminate the 'click,' but I need to be able to identify a problem by sight as well as by ear. If it disappears without my being able to see it, I will, of course, save the file, but no learning will take place.

My question is, "how do you see a click"? I have magnified both the height and length of the waveform to the maximum area viewable on my monitor. I keep looking for some disconnect point on the waveform, but see none. Perhaps I don't know what to look for???

Any help would be humbly appreciated.

Hummingbird

Subject:RE: Showing my ignorance!

Reply by: MyST

Date:3/14/2003 6:25:15 PM

Well you say you've looked for a disconnected area but didn't find any?
Cuz that's usually where it is. You'll see the mismatch at some point.
Did you try overlapping your two sections ever so slightly and adjusting the volume in that section to compensate? Maybe it would work better than trying to match them perfectly.
Sorry if this answer is too basic. Hobbyist on the prowl! That, plus I don't know everything you've tried.

M

Subject:RE: Showing my ignorance!

Reply by: ATP

Date:3/14/2003 6:25:25 PM

hmm .. interesting problem. if you can't actually see the 'click' in the waveform then it seems very hard to find the exact location of it.

but perhaps you can work around this problem by using different mixer settings. how exactly did you mix the two parts together? did you create a fade in for the latter part and a fade out for the first part prior to mixing? if not, that might solve your problem. even if you use very short fade times on both waves, you'll be certain the values start and end at 0 value, thus eliminating a possible click. especially the fade in of the latter part should help with this.

another option is that you change the duration of both audio clips and mix them together at another point than you first used.

if you were just interested in the theory of visualizing sound in Sound Forge then i apologize for my non-related post. :)

Subject:RE: Showing my ignorance!

Reply by: musicvid10

Date:3/15/2003 1:53:07 AM

You will see a sudden variation or direction change at the point of insert. That's what causes a click.

The way around this is really quite simple, and doesn't require you to be a rocket scientist. Your cut and insert points should be at zero-crossings -- no click!

Subject:RE: Showing my ignorance!

Reply by: MarkWWW

Date:3/15/2003 8:17:17 AM

Most clicks are pretty obvious on the waveform display, but sometimes you do get a situation where a quite noticeable click in the audio isn't at all evident in the waveform display.

In these situations I have found that a way that works is to make a selection of a couple of seconds worth of audio that includes the click at its end and then to keep playing the selection while gradually reducing the length of the selection. Eventually the click is no longer heard and you have found where it is - just after the currently selected bit. If necessary you can do a similar thing with a selection that includes the click at its start and gradually move the start point of the selection later and later until it no longer includes the click. Again you have found the location of the click - just before the current selection.

Once you have bracketed the click to a very narrow selection like this you may find that you can now see where the click is after all, but if it still isn't apparent you will usually have got close enough to it that simply using the Sound Forge Glitch Repair tools on the small section where the click is will get rid of it even if you still can't say exactly where it was.

But I suspect the real problem may be that you have just butted the end of the second recording onto the beginning of the first recording. This will usually give rise to a click, particularly if care isn't taken to ensure that the waveforms join up smoothly. A useful precaution is to make sure that all cuts are made on zero-crossings of the waveform, but even this isn't enough to prevent clicks completely, particularly when using stereo files where you can't always find a nice place in both channels simultaneously. Better is to make sure that all edits are done by using a quick crossfade from one section to the other - 10 ms or so is about right - to soften the transition.

Subject:RE: Showing my ignorance!

Reply by: Rednroll

Date:3/16/2003 11:22:39 AM

oops...thought I had posted to this one. Wrote a big long "how too" and then lost my internet connection and everything got lost.

The above advice is a good technique. I do a similar method.

1. Hit Play before the click
2. Have your finger ready to hit the "Pause" button
3. As soon as you hear the click hit "Pause"
4. Zoom in a level, move your cursor back a bit.
5. Hit Play to make sure your cursor is located before the click, then use the "stop" key so that your cursor will now return to where you started.
6. If there's too much playback before the click, then nudge that cursor up a bit.
7. Now make a small selection and enable "loop" playback. Make sure it's not too small or you'll never be able to hear the click, because of the constant looping.
8. If you have the click within your loop area now use the "SET VIEW" memory buttons. This essentially captures the click within a box, and you can cursor around in that box until you find it. If you guess wrong of the located click, just click the "view" preset you stored and you're back to your boxed in click.

9. At this point I usually zoom into something like 2:1, and then use the scroll buttons at the bottom of the data window and look for something that has a 90 degree transient (thats the usual click look) located in the selected area I have view memorized.

If you still can't find it, what you really need is a "Scrub" function. Sound Forge does not have this......BUT...here's a trick too achieve it.

Goto the Effects menu with your boxed in click area still selected. Use the PITCH>SHIFT effect and down pitch the selected area -24 semitones. This will eccentially give you a -2X playback speed for that area. Now playback that area and you'll be able to find the click easier at this slower playback. Memorize what it looks like. Now goto the Edit/Undo Pitch shift and reselect your captured view. Now zoom in to a view which resembles the pitch shifted view and match the click with the one you've commited to memory.

Then grab the pencil tool and draw that click out of there!!! I've never missed a click yet. But sometimes I cheat and just use the sonic foundry "Click/Crackle remover" and you can select the area the click is located in, and have the plugin find it for you. Then you have the option of having the plugin do it's thing on the click or grabbing the pencil tool if you like doing it the manual way.