Audacity Forum

Hi,

it all seems a bit confusing to me and it tells me that I cannot rely that everything always can be expected to work reliably.

Anyway, I recognize that I should point out once more that our interface is different from what you know from other devices and what you obviously assume is the same here:

Our Interface supports only one sample rate. This sample rate is the sample rate of the incoming S/PDIF digital audio data stream, which cannot be influenced by the PC or the interface. In order to handle different incoming sample rates, the interface measures the sample rate and offers it to the system as the only available sample rate. When the sample of the external digital audio data stream is changed and the interface notices that, it disconnects from the USB and reconnects as a different device with the actual sample rate. The sample rate is part of the device's name, as you can see on the screen shot.

Yes, in the event of problems you should select the device in Audio MIDI setup, as I suggested in my first reply.

This should also answer your first reply. Sorry when I made it not more clear.

It may well be instructive to see what Audio MIDI Setup reports as your device's sample rate choice(s)

There is nothing that can be set in Audio MIDI Setup for our device. There is only one sample rate, always 24 bit and no volume or other control available. That' exactly how we want it.

What does "open a DAW" mean? A different digital audio workstation software? I tested the recording functions with Audacity and a few other programs (Cubase, TwistedWave, WavePad). All of them worked from the beginning on, only Audacity needed a couple of days to understand what expect from it

Uwe

(once again thanking you for your tips ans answers)

UweB wrote:There is nothing that can be set in Audio MIDI Setup for our device.

Then you have a problem.

There is only one sample rate, always 24 bit and no volume or other control available.

Either you follow "consumer" path, eg 16/48 and Core Audio will resample as needed or you follow the "pro" path in Core Audio. In the latter case, the audio app can set a sample rate and bit-depth. Some DAW's do, others leave that to Audio/Midi setup.

That' exactly how we want it.

Why?

It sounds as if you are trying to compensate for Windows' audio shortcomings by making it worse.

I've never seen any audio interface (from the last 20 years) behave like that...

It looks like we misunderstand each other.

UweB wrote:
>There is nothing that can be set in Audio MIDI Setup for our device.
Then you have a problem.

Why? That's what I expect: Nobody and nothing should be able to alter the audio data. And note that I am able to prove that nothing alters the original data. I have a special digital audio generator where I can send precisely defined digatal audio sine waves, e.g., a sine wave of 100% FS with 1/6th of the sample rate with two samples per wave being precisely 0 (values 0.0, +0.5, +0.5, 0.0, -0.5, -0.5 and so on). I cannot not only demonstrate that in Audacity, but als in a hex editor displaying the .wav file. If you want me to, I can send you such a recorded file or post a screenshot here.

What kind of a problem should there be when everything is exactly how I expect and want it?

There is only one sample rate, always 24 bit and no volume or other control available.

Either you follow "consumer" path, eg 16/48 and Core Audio will resample as needed or you follow the "pro" path in Core Audio. In the latter case, the audio app can set a sample rate and bit-depth. Some DAW's do, others leave that to Audio/Midi setup.

I don't know about consumer and Pro paths in core audio, maybe there is something that I ought to learn. Anyway, I neither can set the interface's sample rate nor does anything resample the data (except Audacity, when I want it to).

>That' exactly how we want it.

Why?
It sounds as if you are trying to compensate for Windows' audio shortcomings by making it worse.
I've never seen any audio interface (from the last 20 years) behave like that...

Maybe we are talking about different things. I have no problem with core audio, no problem with Windows, no problem with resamplers or anything (provided that I set the Project Rate in Audacity to the sample rate of the incoming signal and that I also set the export format to the width of the incoming signal). That's what I learned to be called "bit precise" at some other application. I want that bit precision, I don't want anything to modiy the data. Do I need to justify that or do I misinterpret your question "Why"?

UweB wrote:To the best of my belief, for several reasons this can only be explained by a bug in Audacity:

I don't use Mac OS X, but I do take more than a passing interest in all discussions on this forum.

If I've got this right, you have a unique 24 bit 192 kHz Class 2 USB audio interface, and sometimes it does not work correctly with Audacity, which you believe is due to a bug in Audacity. Is that correct?

What can we do about that? We can't reproduce the problem and we don't have access to the device so we have no way of testing or any type of trouble shooting. As the problem appears to be intermittent, can you be sure that it only occurs on Audacity and not in other audio applications, or could it be that you have only observed the problem in Audacity?

I'm aware that there have been problems in the past for Mac OS X recording 24 bit audio date, which makes me wonder, does the problem occur if you set Audacity to record 32-bit float format?

Audacity uses the Portaudio library to capture audio streams from the computer sound system (http://www.portaudio.com/). If you wish to troubleshoot this issue I think a good place to start would be testing whether Portaudio is able reliably capture data from the device. Clearly we can't do that because we don't have access to the device, and as you have designed it as a unique device, we obviously don't even have anything comparable.

I wasn't asking "why" you designed this device, but the fact remains that even if its sample rate/bit depth choices in Audio MIDI Setup are disabled, selecting the device in Audio MIDI Setup (confirming to the OS that it is default device) sometimes helps Audacity along to record correctly. Why that is the case, I don't know, but it is more likely to be a PortAudio than Audacity issue.

You have two machines running OS X so you could make parallel recordings comparing Audacity with one or more other DAW's so you have a longer run of tests to go on. You can also test PortAudio itself without Audacity, as Steve suggests.

Gale

And a quick note on "magically started working" that I haven't seen pointed out yet:

Operating systems are prone to be set to automatic upgrade these days. If a component on the critical path of your problem was touched, that could explain why it was reliably failing to work, and now it's reliably working. Proving that can be difficult unless you have a wizard handy on the relevant OS, or virtualization, or both.

Hi everybody,

thanks for your answers. I didn't respond for a long time because I had to care much for other things.

Steve, yes, it seemed obvious to be a bug in Audacity. Now that I learned about PortAudio, it might have been there, too. But this crazy situation that on two notebooks the bug disappeared contemporary while nothing else has been changed is still continuing. It would have been difficult enough to fix this assumable bug as long as it exists, but without it it is obviously impossible. Except somebody recognizes from the typical effect what might have had happened there.

It definitely did not appear with other applications and it appeared under all circumstances, particularly with 32 bit an float. But it did not appear when the sample rate was high while the project rate was e.g. 48 kHz. Should PortAudio do the down-sampling, one had to have to look there, should Audacity do it, I would expect the effect located in Audacity.

Meanwhile it works one more Mac correct and whatever it was, it feels like it is over. Knock on wood and cross your fingers.

Gale, whenever it reappears, I will have a closer look at Audio MIDI Setup an whether I can influence something there.

Baylink: One of the Notebooks was a Thinkpad and that definitely wasn't upgraded. But I agree, the effect makes such an upgrade looking obvious.

UweB wrote:It did not appear with other applications and it appeared under all circumstances, particularly with 32 bit an float. But it did not appear when the sample rate was high while the project rate was e.g. 48 kHz. Should PortAudio do the down-sampling, one had to have to look there, should Audacity do it, I would expect the effect located in Audacity.

If the project rate is below the Actual Rate I think you can assume Audacity (more specifically the Libsoxr library) is resampling.

But perhaps you did not do many tests while the problem was still happening, and you can't rule out fluke cases where the audio was corrupted before it got to Audacity.


Gale

UweB wrote:Steve, yes, it seemed obvious to be a bug in Audacity.

If the bug is in Audacity, then if you use the exact same version of Audacity with the exact same setting, then the bug should reappear.
I presume that you have not updated Audacity since you observed the problem, so as far as Audacity is concerned, the only things that could have changed are the settings.
You can reset the settings in Audacity back to their default values as described here: http://manual.audacityteam.org/o/man/pr ... html#reset

If setting the preferences so that they are exactly as they were when the problem occurred does not reproduce the problem, then logically "something else" must have changed, and logically it is most likely that the "something else" is responsible for the problem.