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Offline justink

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Audacity (osx): How to mix two AUD sources?
« on: April 28, 2008, 10:59:25 PM »
doing a SBD > R-09  and a 4023 > Aerco > R-09 tomorrow night.

what's the best way to mix these in post using Audacity... (or some other mac friendly and free application)?

thanks,

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Offline morst

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #1 on: April 29, 2008, 04:54:13 AM »
Let me give it a try for ya. These instructions should work fine on a mac or a PC running Audacity. Probably Linux too, though I have never tried it.

1- Run the masters so the levels peak below -3.0 dB on each if you can, so you can mix them without having to lower volume to avoid clipping peaks. Run them both at the same sample rate. Bit depth is not as important to match. Name each file descriptively including the type of source (Foobar2008-04-29-SBD-24bit.wav, Foobar2008-04-29-DPA-24bit.wav or some such)

2- Go to AUDACITY>PREFERENCES> QUALITY and set your default sample rate and bit depth to the desired settings (44100 with the desired output bit-depth). PROJECT>IMPORT both sources into audacity and FILE>SAVE your work.

3- Use the double-headed arrow "TIME SHIFT" tool in the top left corner (<-->) to line up the files as near as possible to the start of the music. Find a sharp peaking impulse like a drum hit or some other peak to line up and zoom in until they are as precisely aligned as possible.

4- If you think you need to do any EQ or level changes on either source, do this now. You can use EFFECT>AMPLIFY to tell you how high each source peaks. If each source peaks higher than -3.0dB at any point, you will get clipping on the mix, so you'll need to lower levels to avoid this. It is also possible to have one source higher than the other and still clip peaks. I am good but not great at math, so hopefully some other folks can chime in with suggestions and comments regarding levels. I think I have it right, that 2 signals of -3.0dB will add up to peak at -0.0dB so you want to stay below that.

5- Go to the end of the files and figure out how much they have drifted apart. Do some math* to figure out how much you need to use EFFECT>CHANGE SPEED to get them lined up (see below for my method of calculating the percent change)

6- I suggest shortening the longer file rather than stretching the shorter one, but it probably doesn't matter. Use the EFFECT>CHANGE SPEED to do that.

7- Check the alignment to make sure the sources stay together. If they are not correct, use EDIT> UNDO SPEED CHANGE and try step 6 again. When they are correct, FILE>SAVE your work again. As long as you keep the file open, you can UNDO past the file save operation, but once you close and open it again, you can't go back past the saved version.

8- Check the mix for sound by using the MUTE function on each track during playback to make sure it sounds good. Adjust the gain for each track if needed by using the +......- slider on the left of each track for course adjustment, or EFFECT>AMPLIFY for finer control.

9- Go to AUDACITY>PREFERENCES > QUALITY > HIGH-QUALITY DITHER and select "Triangle Dither"

10- FILE>EXPORT AS WAV (or AIFF) to make the mixed file. FILE>SAVE again. If you think you might need to make further adjustments after checking the completed file, keep this project session open so you can UNDO back. Name the file something descriptive like Foobar2008-04-29-MIX-24bit or Foobar2008-04-29-MATRIX-16bit so you can distinguish it from each source file.

11- FILE>OPEN a new Audacity project document and PROJECT>IMPORT the newly created mix file. EFFECT>AMPLIFY to check that all peaks are below -0.0dB. If this plugin does not offer to boost levels, then you probably have clipped a peak somewhere, and you will want to go back to the original files and lower the levels of one or both sources to preserve your dynamics and avoid flattening out peaks. If you have a little headroom and it sounds good, then you have successfully mixed your sources.

12- If you want to track for CD's, then VIEW>SET SELECTION FORMAT > CDDA min:sec:frames 75fps and then EDIT>SNAP TO> SNAP ON to allow you to cut tracks without "sector boundary errors." Select tracks in order by using EDIT> MOVE CURSOR TO TRACK START (I go into preferences and give it a keyboard shortcut to make this easier) then shift-clicking on the end of each track, then EDIT> SPLIT each track apart in order, making sure to split the final track too.

13- FILE> EXPORT MULTIPLE (NUMBERING CONSECUTIVELY) to WAV (or aiff) in your selected target directory.

14- Compress these files losslessly using your favorite FLAC encoder, and upload to your favorite sharing website, and post in the KICKDOWNS thread here so we can check it out.

15- please let me know if this is unclear or can be improved upon.  8)


* oh shoot, now I gotta figure out how to tell you the math part! My apologies for the half-assed nature of this part of my method.  :-[ Go to VIEW>SET SELECTION FORMAT > SAMPLES (SNAP TO SAMPLES) so you can measure the length of your program in samples. Measure the total length from your sync points early in the file to the desired sync points late in the file. You will get different numbers for each file since they are probably not lined up perfectly due to slight variances in the clock chips of the two recorders. Make a note of each of these numbers. Subtract one from the other to find out the number of samples of drift at the end, and write this number down. Divide the length of the longer one by the length of the shorter source and you will get a number close to but greater than 1.0000000. Let's use an example where you have exactly one second of drift at the end of exactly one hour at 48KHz. The longer file is now 172,848,000 samples and the shorter one is 172,800,000 samples. Divide the long one by the short one and you will get 1.0002788. (If I am getting this right, then) this tells you that you that you need to speed change the longer file by -.02788%

Damn I hope I got that right. Please won't someone troubleshoot my math and let me know the best way to do this???  :o
« Last Edit: April 29, 2008, 05:15:05 AM by morst »
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Offline justink

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #2 on: April 29, 2008, 01:50:52 PM »
thanks for typing all of this out!  i'll give it a shot.

i've been told by others to track the show out and line up each individual track, but this method sounds easier for some reason...

-j
Mics:
DPA 4028 (wide cards)
DPA 4023 (cards)
Earthworks TC25 (omnis) 

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bm2p+ Edirol UA-5 (FOR SALE - Make Offer)

Recorders:
Sound Devices MixPre-10T
Oade CM Edirol R-44 (FOR SALE - Make Offer)
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Offline morst

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #3 on: April 29, 2008, 02:10:45 PM »
thanks for typing all of this out!  i'll give it a shot.

i've been told by others to track the show out and line up each individual track, but this method sounds easier for some reason...

-j
Glad it sounds easier. I wish it were simpler, but as Einstein said "Everything should be made as simple as possible, BUT NOT SIMPLER!!"

When you get the speed difference right, you only have to line it up once for each recording.  :)

edit- (Unless the speed of sound varies due to environmental factors such as temperature and humidity such that the sources become mis-aligned. . .)
« Last Edit: April 29, 2008, 09:29:33 PM by morst »
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Offline ajmiller

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #4 on: May 07, 2008, 04:04:22 PM »
Morst


Thanks so much for typing this "How To" out for us here. I have been searching the archives for a couple days trying to find these exact steps! I have a couple shows lined up needing this post processing.

+T

Offline willndmb

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #5 on: November 21, 2008, 01:27:36 PM »
Let me give it a try for ya. These instructions should work fine on a mac or a PC running Audacity. Probably Linux too, though I have never tried it.

1- Run the masters so the levels peak below -3.0 dB on each if you can, so you can mix them without having to lower volume to avoid clipping peaks. Run them both at the same sample rate. Bit depth is not as important to match. Name each file descriptively including the type of source (Foobar2008-04-29-SBD-24bit.wav, Foobar2008-04-29-DPA-24bit.wav or some such)

2- Go to AUDACITY>PREFERENCES> QUALITY and set your default sample rate and bit depth to the desired settings (44100 with the desired output bit-depth). PROJECT>IMPORT both sources into audacity and FILE>SAVE your work.

3- Use the double-headed arrow "TIME SHIFT" tool in the top left corner (<-->) to line up the files as near as possible to the start of the music. Find a sharp peaking impulse like a drum hit or some other peak to line up and zoom in until they are as precisely aligned as possible.

4- If you think you need to do any EQ or level changes on either source, do this now. You can use EFFECT>AMPLIFY to tell you how high each source peaks. If each source peaks higher than -3.0dB at any point, you will get clipping on the mix, so you'll need to lower levels to avoid this. It is also possible to have one source higher than the other and still clip peaks. I am good but not great at math, so hopefully some other folks can chime in with suggestions and comments regarding levels. I think I have it right, that 2 signals of -3.0dB will add up to peak at -0.0dB so you want to stay below that.

5- Go to the end of the files and figure out how much they have drifted apart. Do some math* to figure out how much you need to use EFFECT>CHANGE SPEED to get them lined up (see below for my method of calculating the percent change)

6- I suggest shortening the longer file rather than stretching the shorter one, but it probably doesn't matter. Use the EFFECT>CHANGE SPEED to do that.

7- Check the alignment to make sure the sources stay together. If they are not correct, use EDIT> UNDO SPEED CHANGE and try step 6 again. When they are correct, FILE>SAVE your work again. As long as you keep the file open, you can UNDO past the file save operation, but once you close and open it again, you can't go back past the saved version.

8- Check the mix for sound by using the MUTE function on each track during playback to make sure it sounds good. Adjust the gain for each track if needed by using the +......- slider on the left of each track for course adjustment, or EFFECT>AMPLIFY for finer control.

9- Go to AUDACITY>PREFERENCES > QUALITY > HIGH-QUALITY DITHER and select "Triangle Dither"

10- FILE>EXPORT AS WAV (or AIFF) to make the mixed file. FILE>SAVE again. If you think you might need to make further adjustments after checking the completed file, keep this project session open so you can UNDO back. Name the file something descriptive like Foobar2008-04-29-MIX-24bit or Foobar2008-04-29-MATRIX-16bit so you can distinguish it from each source file.

11- FILE>OPEN a new Audacity project document and PROJECT>IMPORT the newly created mix file. EFFECT>AMPLIFY to check that all peaks are below -0.0dB. If this plugin does not offer to boost levels, then you probably have clipped a peak somewhere, and you will want to go back to the original files and lower the levels of one or both sources to preserve your dynamics and avoid flattening out peaks. If you have a little headroom and it sounds good, then you have successfully mixed your sources.

12- If you want to track for CD's, then VIEW>SET SELECTION FORMAT > CDDA min:sec:frames 75fps and then EDIT>SNAP TO> SNAP ON to allow you to cut tracks without "sector boundary errors." Select tracks in order by using EDIT> MOVE CURSOR TO TRACK START (I go into preferences and give it a keyboard shortcut to make this easier) then shift-clicking on the end of each track, then EDIT> SPLIT each track apart in order, making sure to split the final track too.

13- FILE> EXPORT MULTIPLE (NUMBERING CONSECUTIVELY) to WAV (or aiff) in your selected target directory.

14- Compress these files losslessly using your favorite FLAC encoder, and upload to your favorite sharing website, and post in the KICKDOWNS thread here so we can check it out.

15- please let me know if this is unclear or can be improved upon.  8)


* oh shoot, now I gotta figure out how to tell you the math part! My apologies for the half-assed nature of this part of my method.  :-[ Go to VIEW>SET SELECTION FORMAT > SAMPLES (SNAP TO SAMPLES) so you can measure the length of your program in samples. Measure the total length from your sync points early in the file to the desired sync points late in the file. You will get different numbers for each file since they are probably not lined up perfectly due to slight variances in the clock chips of the two recorders. Make a note of each of these numbers. Subtract one from the other to find out the number of samples of drift at the end, and write this number down. Divide the length of the longer one by the length of the shorter source and you will get a number close to but greater than 1.0000000. Let's use an example where you have exactly one second of drift at the end of exactly one hour at 48KHz. The longer file is now 172,848,000 samples and the shorter one is 172,800,000 samples. Divide the long one by the short one and you will get 1.0002788. (If I am getting this right, then) this tells you that you that you need to speed change the longer file by -.02788%

Damn I hope I got that right. Please won't someone troubleshoot my math and let me know the best way to do this???  :o
thanks
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Offline djs

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #6 on: January 09, 2009, 03:35:36 PM »
Thanks!  Here's an obligatory thread bump for your great post.

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #7 on: January 09, 2009, 04:21:59 PM »
thanks a lot! an excellent "How To..." reference...+t for your good karma
« Last Edit: January 09, 2009, 07:08:44 PM by macacopowa »
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Re: Audacity (osx): How to mix two AUD sources?
« Reply #8 on: April 12, 2009, 03:45:22 PM »
mucho thanks for your efforts morst.  this was very simple to read and apply.   sure is time consuming but worth the wait.  upping something right now ;D

Offline georgeh

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #9 on: November 10, 2009, 12:13:19 PM »
mucho thanks for your efforts morst.  this was very simple to read and apply.   sure is time consuming but worth the wait.  upping something right now ;D

bump for a thank you. still not sure if i can pull this off, but it wont be from lack of knowledge now :)
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Re: Audacity (osx): How to mix two AUD sources?
« Reply #10 on: November 10, 2009, 03:36:30 PM »
I've spent most of today trying to do this with XP, crashes every time when i add time? About ready to give it up, but I do have some spare time to play with it more.
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Offline acidjack

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #11 on: January 22, 2010, 08:03:57 AM »
Just wanted to post a thank-you for this; extremely helpful.

One thing I didn't try, but am curious if others have, is if you can avoid the 4ch>2ch WAV>mix/track 2ch WAV>FLAC step and somehow track and amplify the 4ch WAV?  I assume it's tougher because it is hard to make your file peak at -0.1 and preserve the mix you want, but if anyone has tried this, I'd be curious to hear it.
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Re: Audacity (osx): How to mix two AUD sources?
« Reply #12 on: January 22, 2010, 08:24:22 AM »
Just wanted to post a thank-you for this; extremely helpful.

One thing I didn't try, but am curious if others have, is if you can avoid the 4ch>2ch WAV>mix/track 2ch WAV>FLAC step and somehow track and amplify the 4ch WAV?  I assume it's tougher because it is hard to make your file peak at -0.1 and preserve the mix you want, but if anyone has tried this, I'd be curious to hear it.

Very often - you'll need that extra headroom. - When the sources combine, certain frequencies reinforce each other and produce peaks that will be louder than the individual sources peak. Keep an eye on the Audacity meters - playback peaky areas and watch for red in the meters. Red is bad.

Point is - the levels in the individual tracks dont reflect levels on the final export. Pumping up the individual levels to max before combining will almost guarantee a bunch of overs.

Offline page

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #13 on: January 22, 2010, 09:48:57 AM »
Just wanted to post a thank-you for this; extremely helpful.

One thing I didn't try, but am curious if others have, is if you can avoid the 4ch>2ch WAV>mix/track 2ch WAV>FLAC step and somehow track and amplify the 4ch WAV?  I assume it's tougher because it is hard to make your file peak at -0.1 and preserve the mix you want, but if anyone has tried this, I'd be curious to hear it.

Very often - you'll need that extra headroom. - When the sources combine, certain frequencies reinforce each other and produce peaks that will be louder than the individual sources peak. Keep an eye on the Audacity meters - playback peaky areas and watch for red in the meters. Red is bad.

Point is - the levels in the individual tracks dont reflect levels on the final export. Pumping up the individual levels to max before combining will almost guarantee a bunch of overs.

Agreed, I find that I need up to 4-5db of headroom in the unmixed sources to prevent overages in the final rendering which usually lands within 1db. Often times, I'll actually drop 5 or 6db off of the raw sources, adjust wildly for a bit to see what I like as a tendancy, mix carefully in the realm where I found an inkling, and then write down the ratio of db between the two. Then I'll set my amp settings so I'll have the required headroom and the ratio and then render.

edit: forgot the second half of the question...

You can track in audacity at 4ch and thats preserved in the mixdown, and you can amplify just certain tracks in a 4ch wav file, but you have to associate the tracks seperately (if they come in as mono tracks then you are fine) or create stereo associations in audacity. Neither requires a render to wav, but it's a work-around. A rule of thumb is, if you have to use the mix/render or save as to Wav function more then once in the entire process in audacity, you either are using multiple programs in your workflow or you are doing an extra step somewhere.
« Last Edit: January 22, 2010, 09:52:05 AM by page »
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Offline doodee

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #14 on: September 27, 2010, 11:02:06 PM »
El referenco.
An instrument that converts sound waves into an electric current >
an electronic amplifier which precedes another amplifier to prepare an electronic signal for further amplification or processing >
a device to capture an analog or digital source and store the encoded data in a digital format.

 

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