[Bug] Windows calls have sound artifact

[Psayker]

When make calls from windows outgoing audio steam can have sound artifact.

[igsha]

DirectSound

The root of the problem is a directsound element from GStreamer that produce sound artifacts by itself. It can be reproduce by audio recodring and playback (num-buffers=2000 - is about 20 seconds):

$ gst-launch-1.0 -e directsoundsrc num-buffers=2000 ! audioconvert ! audioresample ! opusenc ! oggmux ! filesink location=out.ogg
$ gst-launch-1.0 filesrc location=out.ogg ! decodebin ! audioconvert ! audioresample ! autoaudiosink

Currently DirectSound is depretected. It seems no one is interested to fix this problem in gstreamer.

Wasapi

The successor of directsound element is wasapi - wasapisrc and wasapisink. The pipeline to test wasapisrc audio recording:

$ gst-launch-1.0 -e wasapisrc num-buffers=2000 ! audioconvert ! audioresample ! opusenc ! oggmux ! filesink location=out.ogg

There is no sound issues with this element. But capabilities are very limited. Also it is impossible to change volume level of the microphone directly from gstreamer.

Wasapi2

The more advanced successor is a wasapi2src element. But it is not available in mingw environment and I don't know all characteristics. It is available starting from Windows 10.

Comparison

The comparison of different audio recording elements from gstreamer:

characteristic	directsoundsrc	wasapisrc	wasapi2src
format caps	S16LE	only F32LE	both F32LE and S16LE
rate caps	any	only 44100	any
channels caps	1 or 2	only 2	any
can gstreamer change microphone volume level	yes	no	yes
sound artifacts	yes	no	unknown

[mxlgv]

Fixed: #54