Recorded tracks not syncing up

[fr491355]

I've been using Audacity for awhile now, and i've never had any major issues. So far everything has worked great, except when I get into recording several tracks they end up out of sync. I'm not sure if it's recording the new tracks too slow, or playing back the old ones too fast. It's not terribly out of sync, but if a song is several minutes long, the tracks will be off by seconds. They always start out aligned properly, but towards the end some tracks end up lagging behind. I've been using the "change tempo" effect to resync them up, but I was looking for a less tedious approach.

I'm using version 1.2.4, on Windows XP SP2, with an Audigy. Any and all help/comments would be appreciated.

[manguiko]

HI fr,

I had the same problem some time ago and gave up.

But recently I re-visited, got some good advice here, and went back and tried again, and I don't find the problem, nor the cause.

I am using version 1.2.6, though, and I frankly don't recall if I have changed versions since the problem. So maybe try the latest version.

I was also told that if I have a 'throw-in' sound card with not too good design, that could be the cause. But I do have one that is not too bad.

[steve]

If you are recording at 44100 Hz, try 48000 Hz, If you are recording at 48000 Hz, try 44100 Hz.
Make the change by going to "Edit > Preferences > Quality" and setting the default sample rate.
No guarantees, but it may improve things - let us know how you get on.

[t9bailey]

I am having the same problem now.

I'm getting kind of pissed that this is starting to have all of these technical hangups that were not there before. I am on the verge of uninstalling it and then reinstalling it.

[t9bailey]

Solution:

http://www.youtube.com/watch?v=tXbImBRO5_I

[steve]

That's a useful video clip t9bailey, thanks.

I notice there is a comment on that page

My only question is... how do you know you started to record the two tracks at he exact same moment?

The answer to this is:

Record the first track (I just generate a click track for this as it produces nice distinct timing marks)
Then record that click track as it plays from track one onto track two. (this can be done by recording "stereo mix", or simply placing your microphone close to the computer speakers)

You then have a copy of track one on track two, and any difference in the position along the time line is a clear indication of the latency that needs to be corrected.

The offset been track 1 and track 2 indicates the latency that needs to be corrected.

Screenshot.png (44.66 KiB) Viewed 1295 times

By zooming in on the selected region, we can adjust the selection and read the necessary correction more accurately.

Zooming in on the selected area allows more precise measurement.

zoom in.png (4.21 KiB) Viewed 1295 times

In the second image, we can see that the necessary latency correction is -87 milliseconds (minus 87).

in Audacity 1.3.5, Latency correction is handled automatically, though you can still adjust it in preferences to get it more accurate. This screen shot shows the default (automatic) adjustment in Audacity 1.3.5,

The little arrows at the beginning of track 2 (see illustration) indicate that part of track 2 has become hidden behind the "time=0" start point, due to the latency correction that has automatically shifted the recording a little to the left to compensate for latency.

You can see in this image that the automatic settings have worked rather well and the two tracks are within a few milliseconds. This slight inaccuracy is virtually unnoticeable, but if I were to be really fussy, I could make a manual adjustment in preferences to adjust it a little.

Audacity 1.3.5 with automatic latency correction.

Audacity 1-3-5.png (6.07 KiB) Viewed 1296 times

This is all fine, so long as the latency remains constant throughout the recording.
On expensive sound cards designed for music, the manufacturers go to great lengths to assure that the latency is not only very short, but also remains at a constant amount over long time periods. The very best cards will have latency of just a few milliseconds, that even after a long recording will still remain in synchronisation. Unfortunately this is not true of cheaper, or general purpose sound cards, which in the worst cases can drift quite markedly over just a few minutes of recording. Such timing variations are beyond the control of Audacity, or any other software.

However, even relatively inexpensive sound cards can usually produce sufficiently accurate timing for all but the most exacting purposes. For example, my old SoundBlaster Live Value (PCI sound card - obsolete, but second-hand value of about $5) will remain within about 0.01 (a hundredth) of a second over a 5 minute recording.

[t9bailey]

I was going to upload the same screenshots and stuff because doing the click track thing was my actual method for getting everything back in sync due to latency.

Oh well. Nice post.

[manguiko]

The problem with tracks not matching up, I wouldn't call "latency" but it may relate, though.

The problem I experience is not with one track recording at the same time (time-shifted) but rather of the time total being larger one from the other, whereas they ought to have had the same TOTAL time duration, because although the contents of one track, are different, the exact same sound file was used to sing or play along.

I don't see where the above video addresses that issue.

[steve]

Does this relate to the issue manguiko ?

This is all fine, so long as the latency remains constant throughout the recording.
On expensive sound cards designed for music, the manufacturers go to great lengths to assure that the latency is not only very short, but also remains at a constant amount over long time periods. The very best cards will have latency of just a few milliseconds, that even after a long recording will still remain in synchronisation. Unfortunately this is not true of (all) cheaper, or general purpose sound cards, which in the worst cases can drift quite markedly over just a few minutes of recording. Such timing variations are beyond the control of Audacity, or any other software.

However, even relatively inexpensive sound cards can usually produce sufficiently accurate timing for all but the most exacting purposes. For example, my old SoundBlaster Live Value (PCI sound card - obsolete, but second-hand value of about $5) will remain within about 0.01 (a hundredth) of a second over a 5 minute recording.

[fr491355]

I just downloaded the 1.3.6 beta... All my timing issues have been fixed. Latency wasn't the problem (although thanks for that video it helped) but the playback track was actually playing faster than the record track, this is no longer a problem though. THANK YOU SO MUCH, this makes recording so much easier.