R24 Quantization when importing WAV files

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Zoom mcm
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R24 Quantization when importing WAV files

Post by Zoom mcm » Tue Mar 28, 2017 2:55 pm

I use the R24 for recording either live or by importing WAV files from our band members.
Typically, one will produce a track on his computer 's DAW or from his non-ZOOM recorder and send the stereo WAV file at 44,1 KHz and 16 bits at, say 124 BPM (he used a metronome, but I only receive the instrument sound).
I create a project at 44,1 KHz and 16 bits, set the tempo at 124 BPM, import the WAV file through the R24 USB READER function to the AUDIO sub-directory of the R24 Project and assign the WAV file to a pair of tracks (StereoLink), making sure the tempo of that track is also 124 BPM.
At the same time, I assign a R24 rythm to another pair of tracks (Stereo Link), making sure the tempo is also 124 BPM.
Typically, after that, I will see that the imported WAV file has an intriguing, say 93,5 BPM, according to the R24.
HOWEVER, after maybe 20 such importing, the synchronization has ALWAYS been perfect, whether or not I adjusted that 93,5 BPM to 124 BPM.
It is as if the R24 managed to synchronize everything without me have to even work for it.
AND, s far as I can hear, the pitch has not changed.
The reason of this post is the following: how does it make it? Is there some hidden documentaton that could help me understand how the R24 does that?
Many Thanks
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Re: R24 Quantization when importing WAV files

Post by Wulfraed » Wed Mar 29, 2017 9:59 am

It is unclear just where you are importing into...

Are you setting the import as a "sampler/loop"? That is the only section that I've found BPM change listed (pg 60 of the manual). And also where BPM makes sense for purposes of repeats.

Normally, BPM does not apply to a WAV file, per se. A WAV file, by definition, has so many data points per second (44.1k or 48k), regardless of underlying content. WAV files imported as just mixer tracks are as-is (you can use the time-stretch operation to correct for mismatches of the type mentioned below)

There can be mismatches -- due to slight variations in the internal clock frequencies of different devices. Many years ago I once ran a comparison between: Canon Optura 40 (miniDV standard definition), Canon XH-A1 (HDV), H2, HD16, BOSS BR600, Superscope (check my signature block), and maybe the R16.

I started all the devices, then did one hand-clap as a start signal. After ~30 minutes I did a second hand-clap as the stop point and shut down the devices. Copied the files to my computer, loaded them in Sony Vegas Pro. I adjusted (shift left/right) the files until the start clap aligned for each audio source. Scrolled to the stop clap, and zoomed in.

I took the video files as "truth" as video alignment needs to be more precise than audio. I had one audio device that ran short (as I recall), and others that ran long. Short means the device clock was running slow, so fewer data points were captured, long meant a fast clock. The worst devices were the Zoom products -- one of which ran 15 video frames long (or a half second misalignment after 30 minutes).
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Baron Wulfraed
IISS Elusive Unicorn (detached)

Superscope PSD-300; BOSS BR-600, Zoom HD16cd, Zoom R16, BOSS BR-800, Zoom H2n
Now to (re)learn to play an instrument

Lanikai S-C, SMC-E; GoldTone Banjo-Uke; Flatiron 1C, A5; Big Muddy M1-W; Ovation MM68AX; Ovation CSE-44; Orpheus Valley Fiesta FS; Taylor NS-72ce, T5-S1; Musima (4st, 20 fret, tenor-tuned) banjo; bongos, dumbeks, bodhrans, hand drum, tambourine; recorder: soprano, alto, tenor; Cedar Flute (5 sizes); Pennywhistle (3 keys); Casio keyboards

Zoom mcm
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Re: R24 Quantization when importing WAV files

Post by Zoom mcm » Wed Mar 29, 2017 1:09 pm

Many thanks.

You ask: It is unclear just where you are importing into...
I don't sample/loop.
I import as follows:
Using Windows 10 File explorer, I do the following:
1. The R24 is connected as a card reader to the computer through USB and powered by it.
2. On the R24 I select USB then READER then ENTER.
3. W10 recognizes the R24 as a normal directory (a HDSC card).
4. I Copy/Paste a WAV file from a standard directory DIRECTLY to the AUDIO subdirectory of the R24 Project Directory, as seen by Windows 10.
5. Then, I eject the R24 in W10, and the EXIT the READER on the R24.
6. I Power on the R24 as a stand-alone recorder.
7. As decribed in my original post, I assign the WAV to a pair of tracks. etc.

The problem is: I can't understand how the R24 synchronizes THE BEGINNING of each and every WAV file almost perfectly.
It is as if the R24 analyses the WAV file and synchronizes the start of the selected R24 Rythm perfectly.
Naturally, the WAV file has been produced by rogourously following the selected BPM, say 124, and the R24 is instructed to beat at the same selected BPM (124).

Hoping this is clearer. Don't lose too much time with this: so far, it works so well that we are astonished. We are just trying to understand the inner workings of the R24...

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