Still hearing clicks... and time shift

[allrightythan8]

Hi again,

I have just finished recording some chords, and decided to cut some of the soundwaves out to help with tempo among other reasons. I have made sure all the waveforms look relatively smooth yet there are still distinguishable clicks (three to be exact in this audio clip I uploaded http://uploading.com/files/A4SEO15G/stand by me.mp3.html) I have tried selecting the audio and using click removal on both extremes of the two settings and the audio seems to stay the same... I have read into the wiki page on click removal and tried some of the options presented there. Isnt there just an easier way for the program to smooth out the wavelengths automatically so there are no clicking sounds due to edited audio?

One other problem im having has to to with a time shift.... While Im recording everything is hunky dory on tempo and such... however when i hit the stop button after recording... the audio stream shifts suddenly to the left about a tenth of a second.... I know i can just move it back forward a tenth but id like to know what the root of the problem is

[kozikowski]

If each and every edit seems to click, you may have DC in the capture or raw work. Before you edit anything, Select All and Effect > Normalize, but not actually normalize, just use the Remove DC part of that tool. I bet all your clicks go away. I have one USB audio device that leaks DC Voltage into the sound during capture. The track is uneditable until I get rid of it.

Koz

[steve]

The forum software does not like that link because of the spaces in the name. If anyone wants to download that clip, copy and paste this link:

Code: Select all

http://uploading.com/files/A4SEO15G/stand by me.mp3.html

You do not appear to have any problems with DC offset, so no worries with that. The problem is with the exact position that you start and end your edits. In this close up from your file, you can see where the edit was made and you can see that the wave jumps suddenly upward as it moves across the edit boundary.

edit-point.png (27.17 KiB) Viewed 1104 times

To avoid this from happening, you need to make sure that your edit points occur where the waveform is close to the centre line. This is called a "zero crossing point". An example is shown below.

zero-crossing.png (24.87 KiB) Viewed 1104 times

Sometimes there may not be a zero crossing point available that is close enough to where you make the edit (most often happens with stereo recordings) in which case you will need to repair the click. To do this, zoom in very close on the click and use the "Repair" effect.

Switching to the "spectrum" view can make it easier to find where the click is. Click on the little arrow next to the track name to select the spectrum view. In the picture below you can clearly see the click shown in the first image as it shows up as a vertical line:

spectrum.png (158.42 KiB) Viewed 1113 times

[steve]

While Im recording everything is hunky dory on tempo and such... however when i hit the stop button after recording... the audio stream shifts suddenly to the left about a tenth of a second....

This is caused by the "latency correction". The reason for latency correction is because there is always a small delay between the sound going in through the microphone and getting written to the hard drive. This would cause a problem if you were listening to one track and recording another because the new track would end up being a little bit late. Audacity tries to correct this by guessing how late the new recording is, and shifting it a little to the left (earlier) to compensate for the lateness (correct the "latency").

Sometimes Audacity is unable to guess the exact amount of correction that is required, so in Audacity 1.3.x you can manually adjust the amount of correction that is applied.
(page about "Audio I/O" settings: http://www.audacityteam.org/manual/inde ... es#Latency )

[steve]

If you are cutting bits out from your recording, or pasting bits in, then making the selection so that it goes up to the start of a strum will help to hide the join. Let's say that we want to make one note a bit shorter:

Poor selection - deleting this selection will be noticeable.

bad.png (10.8 KiB) Viewed 1120 times

Good selection - after deleting this selection the join will occur at the onset of the next beat and will be hidden. Also selecting zero crossing points will allow the join to match up and will be totally invisible.

good.png (10.65 KiB) Viewed 1119 times

[kozikowski]

<<<Sometimes there may not be a zero crossing point available that is close enough to where you make the edit (most often happens with stereo recordings) in which case you will need to repair the click. To do this, zoom in very close on the click and use the "Repair" effect.>>>

But still, in order to avoid creating damage in the first place, you could use a very rapid cross-fade. Some very early video editors did this all the time. I caught them at it when they were a little too blatant once or twice.

Koz

[steve]

you could use a very rapid cross-fade.

Yes indeed you can, but using the "Repair" effect gives just as good results, and (in Audacity) is quicker and more simple to achieve.
There is a feature request that could make the cross-fading option (using envelopes) a more practical alternative (and a very useful alternative with certain types of material) http://audacityteam.org/forum/viewtopic.php?f=20&t=7819

In the majority of situations, where the other guidelines regarding selecting a good edit points are used, neither cross fading, or Repairing are likely to be necessary.