Sync bug

[Ito]

Hi,

I think I've discovered a minor bug in Audacity...

Has anyone else had the problem where -

okay: I created a drum sound with the drum machine (Risset i think its called)

and then I repeat the sound 100x for a song.


But the problem is upon looking closely at the time line, the beat does not stay even after a while,
you lose a fraction of a second or two...

Is there a way to help this?

Thanks.

[Gale Andrews]

... I created a drum sound with the drum machine (Risset i think its called)
and then I repeat the sound 100x for a song. But the problem is upon looking closely at the time line, the beat does not stay even after a while, you lose a fraction of a second or two...

So you are not talking about a problem that the drum repeats are being created short, but that what you record against that drum beat gradually gets out of synchronisation with the beat?

Obvious things to check:

* Use the same device to record and play back with in the Audacity Audio I/O Preferences

* Set the project rate bottom left of the screen to a rate your sound card supports (44100 Hz or 48000 Hz should work)

* If that does not help, make sure the drum track is at the same rate (stated above the mute/solo buttons) as the project rate. If not, click above those buttons to select the drum track, then Project > Quick Mix

* If that does not help, make sure you have updated, non-generic sound drivers meant for your specific computer model


Gale

[Ito]

Hi,

Actually I am talking about the drum beat being created short (or is it long?).

Anyways, over time, inspecting the timeline and the beat after about 30 to 40 seconds they do not stay even.

I will work with your suggestions, somehow.


And I think that a click track may just suffice, for the now...

Thanks.

[Ito]

Hi,

Yeah, I just checked.

You can try it yourself:

REPEAT a drum beat 100X, and about 10 or 20 seconds down the timeline it starts losing a fraction of a second.

I should mention however, that I purposely shaved off part of the decay of the beat so it would measure exactly one
second long. Then I could clearly see its evenness (or not) over time.

So there it is.

Thanks.

Help?

[kozikowski]

<<<I created a drum sound with the drum machine (Risset i think its called)>>>

Are you using the sound card in your computer to digitize the analog drum sounds? Nowhere is it written that the sound card that came with your computer has to be the least accurate or stable. This is one of the reasons broadcast systems use external synchronization to expensive time generators when they need 1/30 second accuracy and perfect sync over an hour show.

What usually happens is somebody records a sync track on their Windows machine and then plays it back in headphones to record the second instrument or vocal. Play back the composite and they don't match. The sound card record and play services are slightly out of step with each other.

Especially if you're on a Windows machine, these sound cards are designed to make a Skype phone call, not a theatrical presentation.

Koz

[kozikowski]

Oh, and be careful of the word "bug." Bugs are pretty highly defined. Unintentional evil behavior exhibited at will by multiple different people on multiple different machines.

You probably have a bad sound card. Audacity is a complete slave to the computer that's running it.

Koz

[Gale Andrews]

Yeah, I just checked. You can try it yourself:
REPEAT a drum beat 100X, and about 10 or 20 seconds down the timeline it starts losing a fraction of a second. I should mention however, that I purposely shaved off part of the decay of the beat so it would measure exactly one second long. Then I could clearly see its evenness (or not) over time.

No, not here on Windows XP and Audacity 1.2.6, which is why I could only assume you were talking about recording against the beat. There are oddities with Nyquist length generation (only just fixed now in 1.3.8) so that if you generated the same length again in Risset drum, it would not be exactly the same second time. Maybe that is why you had to shave a bit off to make exactly one second. But if you have exactly one second of audio (look at the Status Bar bottom left) and repeat 100 times, the total length is exactly 1 minute 41 seconds.


Gale

[Ito]

Thanks.

Also when I zoomed (CTRL-1) in really close, I got a much better view of the sound sample and saw that it can

indeed be edited to a precise level. Then I think (!) i got an exact beat.


Do you know why - 1 minute 41 seconds? Isn't that incorrect or imprecise?

Is it fixed in 1.3.8?

Thanks

[kozikowski]

Duplicating a drumbeat three times gives you four beats.

Koz