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Gear / Technical Help => Recording Gear => Topic started by: Rick on March 19, 2005, 12:04:22 PM
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What are these sampling rates used for?
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well, 48 is used by many on their DAT decks...I use 48 all the time when ding 24bit since I can't tell a big enough difference between 48 and 96 at 24bit. Some use 88.2 since resampling to 44.1 for audio cd is easier
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I know about 48. The SD722 has both 48 and 48.048
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ADAT compatibility i believe
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interesting..I thought 48.048 was 48, just rounded off....interesting...now you have be interested in what that is about, did some research off google, appears that 48.048 is a slightly different sample rate commonly used when sycning with video sources...reading more to see why now
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explains some of it in this article, very technical
http://www.editorsguild.com/newsletter/MayJun04/mayjun04_23-24_proj.htm
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we use 88.2 a LOT for high res recording that will eventually be brought down to 44.1 It's an easier conversion for the software mathmatically...
h
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we use 88.2 a LOT for high res recording that will eventually be brought down to 44.1 It's an easier conversion for the software mathmatically...
h
QFT!!!
i use 88.2 all the time for the same reasons Heath does.
Hi Heath! 8)
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What are these sampling rates used for?
to match ntsc 29.97 if you shooting 30 fm per second film , then you slow down the audio by 0.o1% to match the video in telesine or editting
, the same with 88 for double sampling
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we use 88.2 a LOT for high res recording that will eventually be brought down to 44.1 It's an easier conversion for the software mathmatically...
h
this was my understanding also, until the moderator of one of the online audio forums (I think it was one of the Pro Sound Web forums) posted that what actually happens is most resampling software upsamples to some high rate (like 300-something KHz) and then brings it down to 44.1, meaning that there isn't any advantage in starting at 88.2 (vs 96) when your final sampling rate is 44.1. I've done a fair amount of searching since I saw that claim and haven't been able disprove it, but there doesn't actually seem to be a lot of info available on that topic in general.
Steve
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Anyone ever offer a 88.2 signal to a JB3..?
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Anyone ever offer a 88.2 signal to a JB3..?
dude...
the JB3 is a cheap 16bit, low sample rate device (44.1/48)
use it for that and quit trying to make it do things it has no hope of doing well...remember its made by the kings of resampling; Creative Labs
if you want 24bit or higher sample rates than the JB3 can do, buy a recorder that can handle it
in audio resolution and accuracy costs money, there is no real way around that
boogie
:standsupandapplauds:
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I just fed mine a 88/16 signal - the resulting playback is half speed...
As it recorded..the JB3 displayed 44.1 as the sample rate...
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I just fed mine a 88/16 signal - the resulting playback is half speed...
As it recorded..the JB3 displayed 44.1 as the sample rate...
yeah....cause it resampled ;)
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I just fed mine a 88/16 signal - the resulting playback is half speed...
As it recorded..the JB3 displayed 44.1 as the sample rate...
yeah....cause it resampled ;)
Why do you think it resampled?
If anything - it shows it doesnt resample...twice as many samples at the source - thats why it plays at half speed - its an 88hz signal being treated as if it was 44.1
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I just fed mine a 88/16 signal - the resulting playback is half speed...
As it recorded..the JB3 displayed 44.1 as the sample rate...
yeah....cause it resampled ;)
Why do you think it resampled?
because it was made by creative labs with a non-bit transparant AD at those levels.
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Im using an outboard AD...optical in
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Im using an outboard AD...optical in
yes i know. it resampled the digital input.
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Im using an outboard AD...optical in
yes i know. it resampled the digital input.
resampled it to what?
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44.1 apparantly
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Then why does it play half speed - ?
answer: it doesnt resample...
I bet the JB3 firmware just guessed the sample rate - probably has no programming to actually display "88.2"
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i'm guessing the output is resampling? i didin't see your post about half speed, sorry.
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Ok - I transferred the track to my computer...
Opened in SF7 - Went to "Properties" and changed the sample rate to 88.2 (i think this might just change the header)
Now it plays normal speed...
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do you have an fft to measure all the frequencies you are getting? what did you record?
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I ran the analog out of an MD player into my Behringer Ultramatch A/D which was set to 88/16
Basically just grabbed the closest noisemaker...
Whats fft?
I can set up a better test...
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I just fed mine a 88/16 signal - the resulting playback is half speed...
As it recorded..the JB3 displayed 44.1 as the sample rate...
yeah....cause it resampled ;)
No it didn't actually. The sample rate is nothing more than header info used for playback - how fast should it consume samples. When recording thru optical in, the JB3 just writes data as it comes in. It's not resampled or reclocked to anything. Every sample is written, unless you feed it too quickly, in which case it drops samples. I tested 96k and the JB3 could not keep up, but it's possible that it could keep up at 88.2 (doubtful but possible).
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if it does do 88.2 successfully, what really is the point? its hard to tell 48khz from 96khz in the 24 bit world (for most folks anyway), i'd imagine telling 88.2 from 44.1 in the 16 bit world wouldn't really be that evident.
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Like somebody else said, the seemingly strange sample rates of some of the more professional boxes are meant to deal with "pull up" and "pull down" situations encountered in post production. On a film shoot, most people shoot (record) audio at 30 fps, with a set time code generator acting as the master. The camera operates at 24 fps. During telecine, in order to frame-match NTSC video speed, both the camera and the audio need to be slightly slowed down in order to sync. That's what gives the .01% difference. Now, you may ask, why would you record at 48.048k or 44.156 when you're pulling down in post-production. The answer is that for movies t hat are never going to be re-released in theaters that it's easier to just record audio at just slightly faster than film speed, knowing all along that the final output will end up at video speed (.01% slower again) and be more compatible with most editing systems.
In other words, if you shoot a movie at 48.048, you don't need to pull down to 47.952Hz during the editorial process. You can, instead, submit video-speed audio that will enable just about anybody to work on the movie without the need of high-end equipment (TDM Pro-Tools, or Nuendo with Timelock and Blackburst). If you have any questions about this crap, please email me at stuart@soundbreeder.com