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January 07, 2008, 01:42:51 AM
62897 Posts in 6243 Topics by 2196 Members
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Topic: downsampling  (Read 133 times)
« on: January 01, 2008, 03:52:21 AM »
dobro Offline
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I recorded a session at 96000 Hz, but I want to convert that to 44100 to mix.  What's the simplest way to do this?  The only way I can think of is to open a new session at the new 44100 sample rate, import one track at a time from the 96000 sample rate session, and then painstakingly line them up correctly by opening two instances of Au, one with the old session and one with the new, and comparing the start points for each clip.  Is there an easier way?
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Reply #1
« on: January 01, 2008, 07:23:32 AM »
Despised7 Offline
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File > Save Session As

Make sure "Save copies of all files" is checked.

Check the options button in the dialog to change the sample rate settings.
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Reply #2
« on: January 04, 2008, 12:41:17 AM »
dobro Offline
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Okay, thanks for that.  You will now no longer be Despised 7 - henceforth you shall be known as Esteemed 1.

And straight from the For What It's Worth Dep't: I did the sample rate conversion twice, once in Cool Edit and once in Au3.

1  First time in Cool Edit 2.1.  I selected the highest quality filter setting - 999.  It took forever, something like half an hour.

2  Second time in Au3.  I selected the highest recommended setting - 400.  It was very fast compared to Cool Edit.  I couldn't hear any difference between the Cool Edit conversion and the Audition conversion.  I followed this up by another conversion in Audition using the highest quality conversion setting - 999.  It took a bit longer, but again, I could hear no difference between the converted session (32/44.1) and the original (32/88).

This seems to bear out what it says in the Help:

"Drag the Low/High Quality slider to adjust the quality of the sampling conversion. Higher values retain more high frequencies (they prevent aliasing of higher frequencies to lower ones), but the conversion takes longer. Lower values requires less processing time but result in certain high frequencies being “rolled off,” leading to muffled‑sounding audio. Usually, values between 100 and 400 are fine for most conversion needs."

Side note: an annoyance in Audition is that it required me to okay each and every track being converted.  By contrast, Cool Edit just went ahead and did the whole lot according to my initial instructions.

Thanks again.

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Reply #3
« on: January 04, 2008, 04:21:16 AM »
MusicConductor Offline
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Dobro, I've noted here in the years past that the sample rate conversion changed with the introduction of Audition.  This was presumably to make processing time more efficient.  However, a quality setting of 999 in AA1.0 and later is the same as 500 in CEP2.1; using the 999 level in CEP2.1 yields the most accurate anti-aliasing known to humanity (pre/post filter set to OFF - you don't need it at that level).

Make a sine sweep at 96KHz, and downsample, and view in spectral view with a really high dB range (like 144 or 160).  You'll see what I mean.

Can we hear a difference?  Nobody's been able to, so far.  This could benefit from a double-blind or ABX test, though.
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Reply #4
« on: January 04, 2008, 05:59:55 AM »
Despised7 Offline
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WWW

Okay, thanks for that.  You will now no longer be Despised 7 - henceforth you shall be known as Esteemed 1.

Thanks Dobro!  grin 


Quote
Side note: an annoyance in Audition is that it required me to okay each and every track being converted.  By contrast, Cool Edit just went ahead and did the whole lot according to my initial instructions.

I believe there is a check box in the "Save Session as" options that says "Remember Settings for Next Time".  If you click that box Audition shouldn't ask you for the file settings more than once.  afro  Groovy.
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Reply #5
« on: January 04, 2008, 07:11:36 AM »
dobro Offline
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Dobro, I've noted here in the years past that the sample rate conversion changed with the introduction of Audition.  This was presumably to make processing time more efficient.  However, a quality setting of 999 in AA1.0 and later is the same as 500 in CEP2.1; using the 999 level in CEP2.1 yields the most accurate anti-aliasing known to humanity (pre/post filter set to OFF - you don't need it at that level).

Make a sine sweep at 96KHz, and downsample, and view in spectral view with a really high dB range (like 144 or 160).  You'll see what I mean.

Interesting about the change from CE to Audition - presumably Adobe did that cuz nobody could hear the difference, so why waste the processing power and the time involved (and yes, I had the pre/post filter engaged - gee, I got a lot done while I was waiting for that file to be downsampled!).

I'll try your test to see what I can see.  But tonight I ran a related test that Ozpeter suggested to me a month ago: I recorded jingling car keys at different rates and compared them (first recording at 32/44.1 and second recording at 32/96).  I couldn't hear a difference.  Then I downsampled the higher rate and compared it to the orginal, and again I couldn't hear any difference.  There might be a difference, of course, which my ears can't hear on my monitors.  But the lovely thing about having the compromised hearing that I do is that if I *do* hear a difference when I'm A/B'ing stuff, then it's an important and significant difference.  I mean, if even *my* ears can hear it, it's there for sure.  grin
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Reply #6
« on: January 04, 2008, 10:48:22 AM »
ryclark Offline
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If you have loads of files to downsample you can do them all using Batch Conversion.
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Reply #7
« on: January 04, 2008, 02:39:43 PM »
beetle Offline
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Using actual music, I have found that a setting of around 350 works best.
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