An introduction to computer audio
WASAPI is Microsoft’s own ASIO, it talks straight to the soundcard if set to exclusive mode.
As it is exclusive mode, no other application can use the sound card.
No more system sounds at full blast over the stereo!
As WASAPI in exclusive mode talks straight to the driver of the audio device, the stream send to this device must match the capabilities of this device in terms of bit depth, sample rate, number of channels and audio format (PCM most of the time) otherwise it is silence.
The program using WASAPI can do this by configuring the audio device to match the source.
In this case we have bit perfect playback.
This allows for automatic sample rate switching as well.
The developer can also choose to adept the source to the capabilities of the audio device.
If the source is mono and the audio device 2 channel, the developer might decide to send the same signal to both channels.
If the sample rate of the source is not supported by the hardware e.g. 192 kHz source with a 96 kHz audio device, the program using WASAPI has to do the SRC (Sample Rate Conversion).
Check if the SRC implemented by this program is an improvement compared with the SRC provided by Windows because writing a good SRC is not trivial.
Obvious using WASAPI in exclusive mode doesn’t guarantee bit perfect playback.
It is up to the developer of the media player using WASAPI to see to it that the playback is bit perfect.
Bit perfect playback is impossible by design if de properties of the audio file e.g. sample rate are not supported by the hardware.
In my perception WASAPI delivers slight improvement in sound quality. Just a little more transparency.
The downside is that is can be a hassle to get it configured right.
If you donít hear a difference you probably better stick to DS (Windows default) for a trouble free performance.