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Double Recording With Audacity (Technical Question)


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Hi

I'm trying to double-record myself (as a concertina+whistle duet) with audacity.

I'm recording the first track and then recording the second one with headers on.

The problem is that the two tracks appear to be shifted by a fraction of a second.

I beleive there is some way to set the "latency time" to fix this but cannot find how

to do that with audacity... can someone help ?

 

NB I'm using a mini-soundcard "Roland Edirol UA-1ex" to do the recoding (with a rode NT2A mike)

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Hi

I'm trying to double-record myself (as a concertina+whistle duet) with audacity.

I'm recording the first track and then recording the second one with headers on.

The problem is that the two tracks appear to be shifted by a fraction of a second.

I beleive there is some way to set the "latency time" to fix this but cannot find how

to do that with audacity... can someone help ?

 

NB I'm using a mini-soundcard "Roland Edirol UA-1ex" to do the recoding (with a rode NT2A mike)

 

There's a time shift tool on the toolbar. click it then you can drag one track to match the other

 

http://www.dropbox.com/s/vnnr7en34kqmawd/audacity.jpg

Edited by spindizzy
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Hi David

 

Edit menu > Preferences > Recording

Adjust the Latency settings; record a click track / metrononome, then a second track in time and calculate the difference (although the playback loop also introduces an extra delay, so you may need to allow for that as well).

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Try this:

 

Record a single transient sound. I used a metal rule slapped against the desk. Essentially the old film-maker's clapper board. You will see the single transient on the track. (A single sound is much easier to deal with than a repetitive one.)

Now patch the output of the soundcard back to the input.

Record a new track. You will now see the original transient on the top track and the recorded copy on the second track.

Click and drag to include the starts of both transients, and press "Fit Selection".

Now that you can see them properly, click and drag from an easily identifiable point on the original transient (eg the top) to the same point on the copy.

Now measure the difference between them in time. You can do this by using the scale across the top, or just accept the figure in the "Audio Position" readout at the bottom of screen. 00.001s = 1mSec.

Go to Edit menu > Preferences > Recording. You will see there is already a default value in Latency Correction. If your copy came later than the original, then that figure isn't big enough, so increase it by the difference you measured. E.G., if the default was -130mSec, and your copy came 20mSec late, increase the correction to -150mSec. Conversely, if your copy came before your original, you decrease the correction. (You probably shouldn't be recording in the Tardis without Dr Who's permission anyway.)

Delete your copy track, and re-record (with the loop-back patch still in place). You'll see the new copy transient record a bit later than the original. But when you hit stop, Audacity will apply the Latency correction, and the copy transient will snap forward, hopefully perfectly into line. You can go through the process again if you need to get even closer.

 

Keep in mind that sound travels 340mm (13.38") in 1mSec. So if you obsess about getting latency down much below a millisecond, you might need to start worrying more about your microphone distance!

 

I'd be interested in any comments about this approach.

 

Terry

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Thanks Terry, I had been wondering what the best way was to tune that setting. Perhaps you could compensate for the speed of sound error (not sure what the technical term is) by recording the second track using the microphone and a speaker instead of a patch cable, and placing the mic the same distance from the speaker as it will be from the instrument when recording for real?

Edited by alex_holden
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Thanks Terry, I had been wondering what the best way was to tune that setting. Perhaps you could compensate for the speed of sound error (not sure what the technical term is) by recording the second track using the microphone and a speaker instead of a patch cable, and placing the mic the same distance from the speaker as it will be from the instrument when recording for real?

 

Sounds reasonable, Alex. I guess if we keep going along this path though, we should also build in some allowance for our reaction time! 152mSec plus a couple of days?

 

Which brings us to that old joke about how the audience always lags when clapping along to the music. "This has enabled scientists in Dublin to calculate the speed of sound through alcohol...."

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You might like to consider using different software. Reaper is a fully functional multi track studio recording package that's free for 60 days and only $60 after that. Its functionality goes way beyond anything Audacity can do. For historical reasons I use Logic Pro in my studio but if I were starting again I would probably go with Reaper.

 

Chris

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Thanks to all !

I've checked the latency time following the suggested methods : 200 ms ! quite deceiving : I'm using a macbookpro and my soundard is supposed to be zero latency :(

Anyway I could correct it as suggested. I should also have a look at reaper.

 

I may post a duet recording in the TOTM someday, but yet I'm not satisfied enough by my first takes.

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Thanks to all !

I've checked the latency time following the suggested methods : 200 ms ! quite deceiving : I'm using a macbookpro and my soundard is supposed to be zero latency :(

 

A misleading expression, I think. Nothing has zero latency - even a piece of wire, although at the speed of light, we can normally disregard it! Normal electronics can be regarded as zero latency for the same reasons. Anything involving computation however has to take time, and that means latency. Laptops tend to have slower computation times as they are designed to be economical of power, which may explain your 200mSec. My office desktop on the internal card takes 150mSec.

 

They possibly mean that the latency is capable of being computed and allowed for, thus effectively becoming zero. Some software (I use Cubase) runs a system test during initial setup which I imagine duplicates the routine I suggested above. After that, no apparent latency. Reaper may well do the same.

 

Or they might mean that the soundcard has its own headphone mix which only involves electronics, not computation, and therefore is effectively latency free as far as incoming material is concerned. The computer will still need to take account of its latency, either automatically or manually as we've discussed.

 

I may post a duet recording in the TOTM someday, but yet I'm not satisfied enough by my first takes.

 

Well, you could try recording the left hand of the concertina on one take, and then overdub the right hand later.... :rolleyes:

Edited by Terry McGee
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Well, you could try recording the left hand of the concertina on one take, and then overdub the right hand later.... :rolleyes:

 

With an English concertina, that might produce some rather "interesting" results, especially if the latency correction isn't perfect. B)

Edited by JimLucas
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Well, you could try recording the left hand of the concertina on one take, and then overdub the right hand later.... :rolleyes:

 

With an English concertina, that might produce some rather "interesting" results, especially if the latency correction isn't perfect. B)

I'd had the same thought, which led me on to trying to find a (genuine, in some form of reasonable circulation, > 4 bars long) tune that could be played on one side of an EC. I've drawn a blank so far - any offers?

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Just thinking about the layout, I'd guess that would be pretty unlikely, or a very weird tune. One might be tempted to think that the One-Note-Polka or the One-Note-Samba would qualify, but I think they are both samples of misleading advertising.

 

I guess one of our programming types could sieve through a very large file of .abc tunes to filter out tunes needing both sides? There might be something left at the bottom of the barrel.

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Just tried Reaper out. Looks good, and seems considerably more intuitive than Cubase. It seems to have dealt with the sound card latency issue automatically, although it didn't seem to run a latency test.

 

I did a quick recording featuring me on guitar, flute, whistle, concertina and voice. It proved conclusively that latency can be the least of our problems!

 

Terry

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  • 1 month later...

Can't help you with that one, MV; not familiar with Mac products. But I have been putting a bit of work into Reaper since seeing it mentioned above and I concur it's good. Quite different in philosophy from other DAEs, so it takes a bit of getting used to. Audacity and Cubase for example have toolbar icons for everything, but Reaper doesn't. It relies on being much more context-sensitive - the right-click options change dramatically depending exactly where you click. When in doubt, right-click. If you don't see the function you need, try right-clicking on another relevant aspect of the display.

 

They do give you a very generous free-trial period (I'm still running on it), so give it a go. You'll soon decide whether it's for you or not.

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  • 5 months later...

I tried Reaper on a couple of small projects but didn't feel that it was as intuitive or usable as advertised, and so I didn't buy it when the trial period expired.

 

Is anyone using Presonus Studio One? It supports Mac and Windows and it has a freeware mode with a reduced feature-set as well as various commercial options. I've had a quick play around and it seems simpler to use than Reaper and the free mode looks like it can do pretty much everything I need for making recordings of my concertina playing (including multi-tracking).

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