What's the "default sample rate" for an AudioDeviceManager?


I’m seeing in the documentation that the AudioDeviceManager::AudioDeviceSetup.sampleRate can be 0, when it indicates “the default rate”.

How can I find out what this “default rate” is? Searching JUCE for default.*rate found only this and one other false match…


There’s no default rate in JUCE for such, since the AudioDeviceManager’s setup is based on the device it’s associated with…


That’s not what I meant.

If you call AudioDeviceManager::getAudioDeviceSetup(AudioDeviceSetup& setup) you can get an AudioDeviceSetup which represents the current device and contains a field called sampleRate.

The JUCE documentation, found in juce_AudioDeviceManager.h, warns you that this field will sometimes be 0, and says that in that case, it represents the “default rate” - but there is no idea of “default rate” in AudioIODevice or in AudioDeviceManager or AudioDeviceSetup.

So what do I do if I see a 0 in this field? Right now I replace it with a hard-coded 44100…

I think that this is a documentation error, perhaps? That sampleRate is only zero if the device hasn’t been opened yet - so if I’m trying to read a device and get a sampleRate of 0, it’s an error and I can’t proceed. Certainly, I haven’t been able to get a sample rate of zero with any devices I checked…


All it means is that if you pass 0 for the rate, then it’ll find out what rates the device supports, and will pick a sensible one - which will usually be the lowest rate that is >= 44100.


OK, now I understand it entirely.

But I don’t think even your explanation is quite true - it doesn’t use the unit’s “default sample rate” - it simply doesn’t change the sample rate at all (which might not be the “default sample rate” if you’ve changed the rate), am I right?

I think the documentation is a little bit misleading because it gave me the impression that you might possibly read this parameter and get a 0, or that sending a 0 might reset the device’s sample rate to its initializated sample rate:

/** The current sample rate. This rate is used for both the input and output devices. A value of 0 indicates the default rate. */
Perhaps change it to something like:

/** The current sample rate. This rate is used for both the input and output devices. Set sampleRate to 0 to keep the existing sample rate unchanged. */
because this makes it clear that 0 is only a possibility on setting, not on reading.


Well, that’s not quite true, each device type could behave differently. Some might have an idea of an existing sample rate, others won’t.

I think the bottom line is: if you don’t care about the rate, pass 0. If you do care, then pass the rate you want!


Got it!

If I can convince you to tweak the documentation so the next guy won’t worry about “what does a sampleRate of 0 mean”?.. :slight_smile:


Ok, I’ll make it a bit clearer!