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[6233638]

I'm wondering if there are any sound cards out there that can output non-standard sample rates - for example 46.08kHz.
Better yet, if they allow that to be continually variable, and have a digital output. (preferably coax)
Even better still, if they are cheap...

I'm wondering if it would be possible to have a setup where the audio is re-clocked, rather than resampled for ReClock/VideoClock during playback. (e.g. 25fps at 24Hz)

Or is that a pointless endeavour, and I'm better off just resampling everything to 192kHz?

[mwillems]

I'm wondering if there are any sound cards out there that can output non-standard sample rates - for example 46.08kHz.
Better yet, if they allow that to be continually variable, and have a digital output. (preferably coax)
Even better still, if they are cheap...

I'm wondering if it would be possible to have a setup where the audio is re-clocked, rather than resampled for ReClock/VideoClock during playback. (e.g. 25fps at 24Hz)

Or is that a pointless endeavour, and I'm better off just resampling everything to 192kHz?

I'm aware of DAC chips (like the AD1859) that claim to allow for continuously variable sample rates, but I've never seen an actual in-box manufactured DAC that supports that option.  Maybe someone else has?

Based on some previous threads, I assume you're just joshing about resampling everything to 192KHz    : http://yabb.jriver.com/interact/index.php?topic=78219.msg532036#msg532036

[6233638]

Well that's just it - I have been looking at getting a new DAC, and a few of them will accept any sample rate within a certain range (28-210kHz with the Benchmark DAC2) but I can't find any way of outputting a non-standard signal from the PC.

And while I don't think it makes a difference to the limits of our hearing (i.e. going above 20kHz) I think a 192kHz output allows for finer sampling in the time domain, which should help reduce errors from re-clocking a 48kHz signal down to 46.08kHz, and then resampling to output at a "standard" rate. (48/96/192)

It seems that ReClock/VideoClock would work a lot better if they were able to have control over the sound card clock, rather than having to resample the audio.

[mwillems]

Well that's just it - I have been looking at getting a new DAC, and a few of them will accept any sample rate within a certain range (28-210kHz with the Benchmark DAC2) but I can't find any way of outputting a non-standard signal from the PC.

And while I don't think it makes a difference to the limits of our hearing (i.e. going above 20kHz) I think a 192kHz output allows for finer sampling in the time domain, which should help reduce errors from re-clocking a 48kHz signal down to 46.08kHz, and then resampling to output at a "standard" rate. (48/96/192)

It seems that ReClock/VideoClock would work a lot better if they were able to have control over the sound card clock, rather than having to resample the audio.

I see, that makes sense; I misread your query.  

Maybe I'm misunderstanding again, but it sounds like as much of a software problem as a hardware one.  Even if you had a sound card that would provide a continuously variable output, how would you feed it?  I guess you're imagining a change in the way videoclock is implemented?  If that's the case, and the benchmark has a continuously adjustable clock, why not just have JRiver take control of its clock in ASIO or WASAPI and vary it appropriately?  Or if the idea depends on the DAC outputting at a standard rate, why not do all the resampling on the front end in software instead of having the DAC do it?  

This sounds like a really neat idea, and I'm trying to wrap my head around it.  Sorry for the stupid questions  

[6233638]

Maybe I'm misunderstanding again, but it sounds like as much of a software problem as a hardware one.  Even if you had a sound card that would provide a continuously variable output, how would you feed it?

Well, I think ReClock already supports this via a registry tweak. (to simply output the exact sample rate to the driver, rather than resampling) But of course pretty much nothing supports it.

I guess you're imagining a change in the way videoclock is implemented?

Hoping for it - if there is hardware that could support this, that is.

If that's the case, and the benchmark has a continuously adjustable clock, why not just have JRiver take control of its clock in ASIO or WASAPI and vary it appropriately?

I have been in touch with Benchmark Media, and they have said that it will accept 28-210 via Coax, 28-96 via Toslink, and their USB driver only supports standard sample rates.
It doesn't sound like they are willing (or able?) to write a new driver that would support this. I don't know whether it's a software limitation of the driver, or a hardware limitation.

Or if the idea depends on the DAC outputting at a standard rate, why not do all the resampling on the front end in software instead of having the DAC do it?

As I understand it, the way that ReClock and VideoClock work, is that they either speed up or slow down the audio to keep it in sync with the refresh rate.
So if you have 25fps video being played back at 24Hz, it's slowed down by 4% - so the audio goes from being 48kHz to 46.08kHz.
It then has to be output at a "standard" sample rate (48/96/192 etc) so ReClock/VideoClock resamples the audio to maintain sync & pitch.

It's my understanding that if you're resampling the audio - especially if you're only making a small change from say 46.08kHz to 48kHz, you are actually degrading the sound quality, because you only have 46,000 samples and need to fill 48,000.
But if you could leave the samples alone, and simply change the speed they are played back at, you could reduce 48kHz to 46.08kHz without actually making any change to the audio file, so it would be a "lossless" change.

[pschelbert]

yes, with RME Fireface UFX for example.

You can adjust pitch in a range of +-5%

However that one is not cheap if you mean really cheap (its around Eur2000.-)
May be you can do that with cheaper RME cards or audio-interfaces. Check the manuals.

[mojave]

Even though the Benchmark DAC2 and other DACs may accept non-standard sample rates, they will still resample and output in standard sample rates. I have a DAC with the Burr-Brown PCM1794 DAC chips. If you look at the specs, the chip will accept from 10-200 Hz. However, its output is dictated by the system clock which is usually a temperature compensated crystal oscillator (TCXO). The output frequency of the TCXO is fixed. You can see that Burson Audio sells a replacement clock available in four frequencies:  Burson Audio Low Jitter Clock. The design of the DAC dictates which frequency is used. You can't change this clock frequency without physically changing the hardware. And if you do change the hardware's frequency, then your DAC will no longer output 44.1, 48, etc. but will now output another set of frequencies.

As a side note, it interesting when you look at the specs that distortion doubles when you go from 44.1 kHz to 96 Khz and again when you go from 96 kHz to 192 kHz.