Project Sample Rate vs Device Sample Rate

Geoff Waddington · 04-05-2009, 04:01 AM

Did a search on the forum and in the manual and can't find an answer.

I notice that I can set:

Options->Preferences->Audio->Device->SampleRate (e.g. 44.1K)

and

File->Project Settings->Audio Settings->SampleRate (e.g. 192K)

to different values.

Does this mean that the internal sample rate is 192k and the I/O is upsampled / downsampled accordingly to 44.1k leaving the nice high internal rate for the plugins -- MMMMMMMM..... :-)

Yeah, yeah I know -- CPU load, but with Gainestown boards around the corner (dual Xeon 55xx -- 16 core HT -- super fast dual path i7 style mem access) seems like if the horsepower is there this could take the 64 bit double precision Reaper philosphy to an even higher level of sonic clarity.

daverich · 04-05-2009, 05:48 AM

I dont know,- but this does highlight a problem when using plugins like melodyne because you can find after bouncedown the 2-track mix has chipmunk vocals even though in realtime it sounds fine...

I'd like it to be clearer which samplerate things are actually working at.

Kind regards

Dave Rich

Geoff Waddington · 04-08-2009, 03:58 AM

Bump.....

No one knows the answer to this?

-- Geoff

Dstruct · 04-08-2009, 06:16 PM

Just try it ...

Geoff Waddington · 04-08-2009, 07:23 PM

I did try it, that's why I'm asking :-)

With project set to 192k and device set to 44.1k I seem to get about 2%-3% LESS CPU usage than when I set both to 44.1k, although I don't have an actual log of CPU usage, I'm just eyeballing performance in Task Manager and Reaper simultaneously in the 2 configurations and it does move around quite a bit.

This is counterintuitive as a higher sample rate should use more CPU.

I thought I must be missing some information that someone here knew about.

BTW I don't get hung up on this stuff -- Reaper sounds damn good -- that's why I use it, I was just curious because of the non-intuitive result.

Still wondering -- Geoff

jonespnice · 04-08-2009, 07:40 PM

Quote:

Originally Posted by Geoff Waddington

Did a search on the forum and in the manual and can't find an answer.

I notice that I can set:

Options->Preferences->Audio->Device->SampleRate (e.g. 44.1K)

and

File->Project Settings->Audio Settings->SampleRate (e.g. 192K)

to different values.

Does this mean that the internal sample rate is 192k and the I/O is upsampled / downsampled accordingly to 44.1k leaving the nice high internal rate for the plugins -- MMMMMMMM..... :-)

Yeah, yeah I know -- CPU load, but with Gainestown boards around the corner (dual Xeon 55xx -- 16 core HT -- super fast dual path i7 style mem access) seems like if the horsepower is there this could take the 64 bit double precision Reaper philosphy to an even higher level of sonic clarity.

Yes it is up sampled, depending on what your soundcard is set up as (44.1k or whatever), but the file->Project Settings->Audio Settings->SampleRate is only used to set your soundcard's samplerate remotely, it does not set project samplerate.

daverich · 04-09-2009, 01:31 AM

Quote:

Originally Posted by Geoff Waddington

I did try it, that's why I'm asking :-)

With project set to 192k and device set to 44.1k I seem to get about 2%-3% LESS CPU usage than when I set both to 44.1k, although I don't have an actual log of CPU usage, I'm just eyeballing performance in Task Manager and Reaper simultaneously in the 2 configurations and it does move around quite a bit.

This is counterintuitive as a higher sample rate should use more CPU.

I thought I must be missing some information that someone here knew about.

BTW I don't get hung up on this stuff -- Reaper sounds damn good -- that's why I use it, I was just curious because of the non-intuitive result.

Still wondering -- Geoff

I would guess that it's because your plugins are no longer spending cpu performing the samplerate conversion themselves when they upsample? - it might be more efficient to do it your way?

Kind regards

Dave Rich

stupeT · 04-09-2009, 01:43 AM

Quote:

Originally Posted by Geoff Waddington

This is counterintuitive as a higher sample rate should use more CPU.

Just a general guess:

The lowest CPU might occur when alle the sampling rates are the same. In example: having all tracks recorded at 88, having all samples of VSTi-samplers in 88 and output also at 88 will not cause any on-the-fly conversions. That saves CPU.

Now using 44 here or there wille cause up/down sampling which uses more CPU.

Lowest CPU will certainly occur when each and everything is in 44.

Art Evans · 05-08-2009, 01:18 AM

This does seem to be an area of slight mystery and confusion...

For instance, at a concert hall here, all audio arrives in madi format and it's at 48kHz, like it or not.

I guess the sensible thing is to have the project sample rate and the rate specified in the preferences to 48kHz, to ensure that everything is running at the same rate.

But what would be going on, internally and also audibly, if you had either or both places incorrectly set to 44.1kHz by accident? And if so, what would be the remedy in post-production?

fladd · 05-08-2009, 01:32 AM

Isn't the sample rate in the preferences/audio/device optional? And isn't there a box with an option to have the project settings set the samplerate of the device?

fladd

Bubbagump · 05-08-2009, 10:56 AM

Quote:

Originally Posted by fladd

Isn't the sample rate in the preferences/audio/device optional? And isn't there a box with an option to have the project settings set the samplerate of the device?

fladd

Err, yes. But that would just be too easy.

He is referring to Options>Preferences>Audio>Device Allow projects to override device sample rate.

maa · 05-09-2009, 01:06 AM

Quote:

Originally Posted by jonespnice

file->Project Settings->Audio Settings->SampleRate is only used to set your soundcard's samplerate remotely, it does not set project samplerate.

In politics the above is called 'disinformation'.

Cheers

maa

bullshark · 05-09-2009, 07:27 AM

Friendly bump because I'd also like to know the significance of those settings, it's quite unintuitive. I haven't used software before where you could set two different samplerate in two different places.

For instance, what would happen if I had the "request sample rate" checked at 48KHz, but my interface was set in hardware (samplerate can't be changed by software on my FA-101, it's a knob in front of the unit you have to turn...) at 44.1KHz, and my project was set at 44.1KHZ too? Would that screw up my audio somehow?