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Author Topic: Audacity (osx): How to mix two AUD sources?  (Read 51756 times)

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Offline TheBishop

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #135 on: May 22, 2020, 09:55:11 PM »
Thanks, I appreciate that. Next up is a Toubab Krewe show that I've been needing to master for several months now.

Offline morst

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #136 on: August 02, 2020, 03:30:14 PM »
Bumping this thread, because I just re-wrote the instructions for my morst-Audio-Speed-Converter.XLSX spreadsheet, which is available for free download still at this link:
https://docs.google.com/spreadsheets/d/1pQGfYwPgBFFzcY5m6aRj-Zbu9HsRumLy-tJB1d8Eufg/edit#gid=583050244


Quote
"This spreadsheet is a tool which can calculate the percent of ""Speed Change"" needed, in order to synchronize two uninterrupted audio tracks, made with different digital recorders which did not have timing clocks locked together.
This tool was made for use along with the Audacity workstation software. Audacity is availble as a free download for PC, MAC, and Linux. This tool's results can likely be used for other workstation software, as well."   


"Before using this tool, the user should precisely locate and mark four points within the two tracks to be synchronized, in order to make find the two values to feed this tool.
To make a track mark (label) in Audacity on PC, use the mouse and click the point in the track, then use Control-B keyboard shortcut, or go to Tracks > Add Label At Selection. On MacOS, it's Command B.
For greatest accuracy over long files, the two points at which the files are be synchronized should be as far apart in time as is practical, that is, one near the start of the shortest segment, and one near the end of it.
As each point is located and marked, the start time of the file to be changed should also be marked.
The two marked start times are where the difference in time between the sync points of the file to be changed may be most easily measured, as the waveform of the first spot moves from its marked location when the user finds the second spot.
Rather than having to find the same bit of the pattern to mark again, it is much easier to simply use the start of the track as a proxy.
If it is not practical to use the start times, the file end points may alternately be used."   
                                       
"To use this tool, the user enters two values, and the desired output is the Speed Change value (% differnce), which can then be used in the AUDACITY workstation software's Speed Change plugin, in order to synchronize the tracks.
The primary version on lines 4-5 allows the user to enter the length of the reference file, in samples, and the number of samples in between the marked start points. (see above)
The optional version on lines 9-10 allows the user to enter two track lengths, in samples. This might be useful for matching a soundtrack to the scratch audio of a video production, for instance, or making guesstimations"                                                                       


comments welcome?!

Offline nak700s

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #137 on: July 05, 2021, 09:56:41 AM »
I'm having a hell of a time right now...

The venue that I have been recording at has given me access to their soundboards so that I can mix them with my audience recordings.  Awesome!  So I take the SBD (recorded at 48k) and my AUD (also recorded at 48k) and load them in to Audacity v2.1 (I was using the newer version until I read this thread so I uninstalled that and installed 2.1).  I lined both of the recordings up at the 0:00:03.725 (178,791 samples) point and then find a common point towards the end of the show, for the soundboard this is 2:12:43.275 (382,237,217 samples) and for the audience this is 2:13:05.196 (383,289,428 samples).  I use morst's Audio Speed Converter spreadsheet:



and I get a % speed change of -0.27527696236864200000.  I put this in to Audacity (without the negative sign) and run the Change Speed effect on the audience recording:


This is where things get funky...

At 0:00:27 the recordings are off by 77 msecs
At 2:15:00 the recordings are off by 500 msecs
but at 1:08:00 the recordings are off by 6 seconds!

This is my first time trying to combine two sources and I'm going nuts.  I don't understand how they could be so close at either end of the show, but so far apart in the middle.

If this is something you plan on doing more often, may I suggest an equipment upgrade...  You may want to consider a 4-track deck that you can record 4 tracks internally.  I use the Sound Devices 744T, and there are several other great options as well, like their Mix-Pre series.  A long set of cables and you're now simultaneously recording all 4 tracks (a pair of mics + a stereo soundboard feed) on the 1 deck.  All four tracks will open in your editing program, and you'll decide what to bring up or down to your liking.  It's about 1000% easier!   :cheers:
Normal: Nakamichi CM-700's >> SD 744T (or) Sony PCM-M10
Normal: Crown CM-700's >> SD 302 >> SD 744T
Fun times: 3 Crown CM-700's >> SD 302 >> SD744T + 2 Nakamichi CM-700's >> SD744T
Stealth: CA-14c >> CA 9200 >> Edirol R-09HR
Ultra stealth: AudioReality >> AudioReality battery box >> Edirol R-09HR
Simple & Sweet!

Offline checht

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #138 on: July 05, 2021, 11:51:50 AM »
If this is something you plan on doing more often, may I suggest an equipment upgrade...  You may want to consider a 4-track deck that you can record 4 tracks internally.  I use the Sound Devices 744T, and there are several other great options as well, like their Mix-Pre series.  A long set of cables and you're now simultaneously recording all 4 tracks (a pair of mics + a stereo soundboard feed) on the 1 deck.  All four tracks will open in your editing program, and you'll decide what to bring up or down to your liking.  It's about 1000% easier!   :cheers:

^ this. 100% agree.
Went from Mix-Pre 3 to 6 for this reason. Had an old pair of mogami 100' cables, added some 50's & 20's from Tgadakis and everything got better. Next we can discuss the ultimate SBD connector field kit 😀.
Schoeps MK41s > nbob KCY >
Naiant PFA 60v > Sound Devices MP-6 II  or  Naiant IPA > Roland R-07
Recordings at LMA: https://archive.org/search.php?query=subject%3A%22Chris+Hecht%22&sort=-date

Offline morst

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Re: Audacity (osx): How to mix two AUD sources?
« Reply #139 on: July 05, 2021, 03:10:32 PM »
You can't always get a cable between the SBD and the best sounding spot, so this technique won't go away just yet.

OH FUCK this shit is all old and probably solved.
nevermind

That correction number is VERY large. Are you sure the stretch/squash requires six seconds of correction?
1052211 is a lot of samples...
Are you certain that both recordings are continuous? No pauses?
I think you should consider using the other set of lines in my spreadsheet and entering the length of the longer section as 382,058,426 and the difference as the number of samples between the early Sync track start point and the later Sync track start point
When you synced at the start and the end, please mark the locations of the file starts, and use the amount of change as the DIFFERENCE.
The length of time BETWEEN the points is only 382,058,426 samples, which I suggest to plug in as the "LONGER" Length.
(I am gonna have to rewrite this spreadsheet soon anyhow so it's good to get clarity/communication issues sorted out.)


** A note for clarity - the speed change is not computed based on the length of the entire fire.
The speed change is computed based on the number of samples between the two sync points on the longer source versus the number of samples between the two sync points on the shorter source.
I find it easier to count the long one and mark the shorter one's movement, which is why I use the set of lines in my sheet where I plug in length and difference.
« Last Edit: July 05, 2021, 03:32:47 PM by morst »

 

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