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wasapi: Add paWinWasapiAutoConvert flag, which sets AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM | AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY for Shared mode streams.

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AUDCLNT_STREAMFLAGS_AUTOCONVERTPCM is required in order to allow for sample rates other than the system mixer configured sample rate. Otherwise, WASAPI is limited to a single system configured sample rate in Shared mode, which is a severe limitation compared to other APIs supported by PortAudio.
AUDCLNT_STREAMFLAGS_SRC_DEFAULT_QUALITY is recommended to be used additionally.
See <https://docs.microsoft.com/en-us/windows/desktop/coreaudio/audclnt-streamflags-xxx-constants> for documentation.

GetClosestFormat is modified to exit early when paWinWasapiAutoConvert is set in Shared mode because we trust the WASAPI conversions to succeed.

We restrict these changes to Windows 7 (and later) because documentation does not clearly state the minimum required Windows version. Windows Vista was not available for testing.

This patch has been in production in OpenMPT (<https://openmpt.org/>) since version 1.27.01.00 (2017-09-27). PortAudio WASAPI Shared mode is the default output device type in OpenMPT for Windows 7 (and later) and also for Wine setups.
This commit is contained in:
Jörn Heusipp 2019-04-01 09:05:18 +02:00 • committed by dmitrykos
commit aa0748a5b5
2 changed files with 25 additions and 1 deletions
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9
include/pa_win_wasapi.h
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@ -78,7 +78,13 @@ typedef enum PaWasapiFlags
/* force explicit sample format and do not allow PA to select suitable working format, API will
fail if provided sample format is not supported by audio hardware in Exclusive mode
or system mixer in Shared mode */
paWinWasapiExplicitSampleFormat = (1 << 5)
paWinWasapiExplicitSampleFormat = (1 << 5),
/* allow API to insert system-level channel matrix mixer and sample rate converter to allow
playback formats that do not match the current configured system settings.
this is in particular required for streams not matching the system mixer sample rate.
only applies in Shared mode. */
paWinWasapiAutoConvert = (1 << 6)
}
PaWasapiFlags;
#define paWinWasapiExclusive (paWinWasapiExclusive)
@ -87,6 +93,7 @@ PaWasapiFlags;
#define paWinWasapiPolling (paWinWasapiPolling)
#define paWinWasapiThreadPriority (paWinWasapiThreadPriority)
#define paWinWasapiExplicitSampleFormat (paWinWasapiExplicitSampleFormat)
#define paWinWasapiAutoConvert (paWinWasapiAutoConvert)
/* Stream state.