Processing KSPROPERTY_RTAUDIO_BUFFER/GET property request, PortCls
calls IMiniportWaveRTStream::AllocateAudioBuffer with
RequestedBufferSize significantly increased. For example, 1920 or 3840
are replaced with 4096.
Such behavior is observed since Win 7 up to Win 10.
In KSPROPERTY_RTAUDIO_BUFFER_WITH_NOTIFICATION processing, requested size is
not changed.
Is there any reason to alter requested buffer size specified by the
client?
Another strangeness found in AudioDG: if the driver returns actual
buffer size greater than requested in
KSPROPERTY_RTAUDIO_BUFFER_WITH_NOTIFICATION, AudioDG immediately
closes pin instance and returns "unspecified error" to its client.
Observed since Win 7 up to Win 10 too.
There is a little difference between Win 7 and Win 10: in further
requests, AudioDG in Win 10 passes the same requested buffer size
(usually 1920 for 48000/16 stereo streams), while AudioDG in Win 7 may
pass the value it previously receives in ActualBufferSize.
In MS docs, a driver is free to increase or even decrease requested
buffer size. Of course, frame alignment requirements are met. For
example, if AudioDG requests 1920 bytes for a 48000/16 stereo stream
but the driver returns 2048 or 4096, AudioDG fails.
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