09194: Using WASAPI doesn't bypass the kernel mixer

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09194	Sound	Trivial	Always	2 days ago	20 hours ago

Tester	tenpar	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS	Windows 10/11 (64-bit)
Status [?]	Direction Needed			Driver
Version	0.278	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	09194: Using WASAPI doesn't bypass the kernel mixer
Description	Normally, when sound is played in WASAPI, the peak meter of the OS playback device is unresponsive to avoid the kernel mixer, but when sound is played with WASAPI enabled in MAME, the peak meter responds (see attached image). It appears that WASAPI is not enabled even if wasapi is set to sound in the mame.ini settings.
Steps To Reproduce	1. Set “wasapi” to sound in mame.ini. 2. Play a sound game with MAME while watching the peak meter of the audio output device on the sound setting screen of the OS.
Additional Information	The same thing happened when used WASAPI with PortAudio.
Github Commit

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Affected Sets / Systems

Attached Files	wasapi.png (674,587 bytes) 2 days ago Uploaded by tenpar

No.23402 hap Developer 1 day ago	PortAudio in MAME used to support WASAPI exclusive mode, not anymore after the rewrite. MAME's WASAPI sound module doesn't support exclusive mode. cuavas could tell you whether or not it's deliberate, and if it's TODO.
No.23403 Robbbert Moderator 1 day ago	This would seem to be a non-issue, but I'll leave it to cuavas to decide.
No.23405 tenpar Tester 1 day ago	The exclusive mode is more appreciated because the sound quality is degraded when going through the kernel mixer.
No.23407 cuavas Administrator 1 day ago	The sound quality isn’t degraded going through the mixer if you set the mixdown format to use a sample rate supported by the sound output hardware and the application produces sound at the mixdown format sample rate. There’s a slight reduction in latency with exclusive mode, but it’s not much Supporting exclusive mode would require a completely separate sound module, and I don’t think it would be worth the maintenance burden. It would also require moving the audio stream mixing into MAME’s sound manager (or implementing it in the sound module itself), while we’re moving in the opposite direction towards having one stream per sound route and letting the sound API deal with mixing.
No.23410 tenpar Tester 1 day ago	Sorry if I misunderstood. I read it as if you were considering mixing sounds output outside of MAME with MAME, but I don't see the need for that. I think that sounds other than MAME can be ignored. I think that's what the exclusive mode is for. However, I somehow understood that it would be difficult to change to exclusive mode now. I tried changing AUDCLNT_SHAREMODE_SHARED to AUDCLNT_SHAREMODE_EXCLUSIVE in two places in wasapi_sound.cpp, built and started the game, and got the following error. I guess various other modifications are needed. Sound: Error initializing audio client interface for output stream :speaker on device
No.23413 Robbbert Moderator 22 hours ago	So, are you happy for this to be closed?
No.23417 tenpar Tester 20 hours ago	Personally, I would like WASAPI to have an exclusive mode, but I leave it to the developers to decide whether to close it or not.