Sample Conversion Rates (Downsampling in pro tools)

[deejaytrixx]

It seems to me that the new version has a dither when you want to go from a higher bit rate to a lower...which makes little sense to me since it has Dither plug-ins standard with every release.

Also, there is no plug-in for downward sample coversions....which is the complete opposite issue from the Dither, because now it seems Pro Tools handles this automatically, and gives you no choice in the matter.

Question is: What have you guys been doing to both downsample and dither:

For instance, I am going from 48k/24bit to 44.1k/16bit. I can slap an L1-L3 on the master buss, set my dither, and then let pro tools down sample it when bouncing..But, I find this COMPLETELY DESTROYS my mix.

I may be having some kind of mental retardation moment, but am I doing something wrong?

 

[bennychico11]

I think you are confusing these terms:
sample rate
bit depth
bit rate
...and what dither does.


Dither only has to do with reducing a higher bit depth to a lower bit depth. For example, when going 24 bit to 16 bit resolution (or as recommended by Digi, even when going from 16 bit to 16 bit). Dither has nothing to do with sample rate conversion. The only way to control the quality of conversion is to change the bounce to disk quality.


When you say completely destroys your mix...what exactly is it doing?

 

[deejaytrixx]

I think you are confusing these terms:
sample rate
bit depth
bit rate
...and what dither does.


Dither only has to do with reducing a higher bit depth to a lower bit depth. For example, when going 24 bit to 16 bit resolution (or as recommended by Digi, even when going from 16 bit to 16 bit). Dither has nothing to do with sample rate conversion. The only way to control the quality of conversion is to change the bounce to disk quality.


When you say completely destroys your mix...what exactly is it doing?

Believe me, I understand the difference, in great depth. the problem is not so much a problem as I am looking for a shortcut.

The normal way I would handle a 48k/24bit to 44.1k/16bit conversion is to first bounce to 44.1/32bit with no dither, then to 16 bit with dither. At that last stage is when I would slap on my last dither and noise shaping algorithm, and publish to disc. There has to be a simpler way...But when I do downsample from 48k to 44.1k using the Tweakhead setting, I am getting absolutely random artificats and noise in the perfectly once good mix.

 

[dean1964]

The random artifacts you are hearing might be due to the fact that it is very difficult for any software to requantize a signal to a lower sample rate, that is not a multiple integer of the original sample rate.

Aside from that, use the sample rate of whatever your final delivery format is, or twice that sample rate. If you are going to CD, and want to record at a higher sample rate, use 88.2Khz. Then the conversion to 44.1 is a much simpler process. ( Just remove every other sample basically, or is it bit?....i cant remember....but still.) In the end the results will most always be better.

There is really not that much of a difference between 48 and 44.1, anyway, just the formats that use them.

Cheers!

 

[MessianicDreams]

Th If you are going to CD, and want to record at a higher sample rate, use 88.2Khz. Then the conversion to 44.1 is a much simpler process. ( Just remove every other sample basically, or is it bit?....i cant remember....but still.)

actually, that's not at all how it works. the file gets basically completely re-sampled regardless of the sample rate its moving from, so the "mathematical" ease of the move has virtually not effect.



Something is wrong in the way the SRC is going on - you should not be able to hear any glitches whatsoever, as PT should be able to SRC without any audible artifacts whatsoever.

 

[bennychico11]

actually, that's not at all how it works. the file gets basically completely re-sampled regardless of the sample rate its moving from, so the "mathematical" ease of the move has virtually not effect.

not to mention if we really want to think that it's "hard" for a computer to do something like SRC....? With today's processing power? That might have been true in the early 90's, but I don't think that's true anymore. But, that's not saying the QUALITY of D/A converters is going to be better.

Something is wrong in the way the SRC is going on - you should not be able to hear any glitches whatsoever, as PT should be able to SRC without any audible artifacts whatsoever.

+1
I would venture to guess that it's NOT a problem with the dither plugin. But a simple test would prove that...just take the dither off and do the SRC to 44.1kHz/16 bit. Same problem? Try another dither plug (like Digi's)
Also, try using something other than the tweakhead setting. I've heard of someone else noticing issues with it.


or, can you upload an audio sample?

 

[deejaytrixx]

Problem solved. A fatal error was occuring in the dithering plug-in I was using. Digi sent a new one over via download and the problem disappeared