Allow user to specify MMDevice when initialising WasapiCapture and WasapiLoopbackCapture

[njbmartin]

My preview issue #123 raised another potential overload, as both WasapiCapture and WasapiLoopbackCapture assume the default device should be used.

Currently, you can only change the device after initialising the instance, but even then, it has already been initialised with the default device settings (eg. WaveFormat), and you can't change the WaveFormat. Correction, it's not initialised unless specified in the overload.

So there are few potential things here:

• Add MMDevice to the beginning of the overloads and assume that null uses default.
• Allow user to customise/change both Device and WaveFormat after the instance has been initialised.
• Allow a user to modify some properties of WaveFormat and apply it to the capture.

[njbmartin]

Corrected myself above.

[filoe]

It is technically not possible to change to device after WasapiCapture got initialized because the initialization process initializes the devices and sets up all native objects based on this device.
However you can change the device by selecting the device before you call the Initialize method. If you change it afterwards, you will have to select to stop capturing and call Initialize again.

I can't add the MMDevice to the beginning of the overloads, because it would be modication which makes existing code incompatible with the new release. Maybe I could add this to a new major release.

Allowing the user to modify some properties of WaveFormat is quite tricky. The WaveFormat gets choosen by the Initialize method. You can't modify it after calling Initialize. Anyway, it is not the purpose of a class, implementing the ISoundIn interface, to do lots of format conversion. For that purpose, there are existing classes you can use to convert the format to whatever you want.
You would have to create an IWaveSource objects based on the ISoundIn objects using the SoundInSource class. Afterwards you can use the common conversion extension methods or extra classes. You can do whatever you want. From changing the samplerate to applying a channel conversion matrix, ...

[njbmartin]

My apologies, I had a feeling that might be confusing.

Let me explain.

Initialise the object:

_capture= new WasapiCapture();

At this point (before you the initialize() method), you can modify the Device it uses with:

_capture.Device = newDevice;

But you currently can't specify the WaveFormat as it doesn't have a set method.

[filoe]

Correct, but as I've said before. You can't set the WaveFormat because it depends on the driver. WasapiCapture chooses a WaveFormat, supported by the driver. If you need a specific format, do the conversion outside of WasapiCapture. Do you need a specific format as output format?

[njbmartin]

Changing the WaveFormat mainly relates to my issue raised in #123 in which I needed to modify the channels.

[filoe]

That issue already got resolved by overloading the ctor...?

[njbmartin]

It did yes, but that assumes the default endpoint is used whereas this issue aims to address the ability to choose any device.

[filoe]

What about this code:

var captureDevice = MMDeviceEnumerator.EnumerateDevices().First(); //implement your logic for selecting a device...
var deviceFormat = captureDevice.DeviceFormat;
var waveFormat = new WaveFormat(deviceFormat.SampleRate, deviceFormat.BitsPerSample, Math.Min(deviceFormat.Channels, 2));
_wasapiCapture = new WasapiLoopbackCapture(100, waveFormat);
_wasapiCapture.Device = captureDevice;
_wasapiCapture.Initialize();

_wasapiCapture...

[njbmartin]

Yep, I've used that code too. Alright, guess I'll close this issue then.

[filoe]

I've added a tiny sample that should demonstrate the whole thing...