Setup AVAudioSession in coreaudio driver, add low latency mode for it

Author: neoharp-dev

CMakeLists.txt

@@ -38,7 +38,7 @@ elseif(NOT BUILD_SHARED_LIBS)
   message(WARNING "Your version of CMake is very old. This may cause linking issues if your dependencies are not in your compiler's default search paths.")
 endif()
 
-project ( FluidSynth C CXX )
+project ( FluidSynth C CXX OBJC)
 list( APPEND CMAKE_MODULE_PATH ${FluidSynth_SOURCE_DIR}/cmake_admin )
 
 # FluidSynth package name
@@ -423,7 +423,7 @@ if ( CMAKE_SYSTEM_NAME MATCHES "Darwin|iOS" )
     check_include_file ( CoreAudio/CoreAudioTypes.h COREAUDIO_FOUND )
     if ( COREAUDIO_FOUND )
       set ( COREAUDIO_SUPPORT 1 )
-      set ( COREAUDIO_LIBS "-Wl,-framework,CoreAudio,-framework,AudioToolbox" )
+      set ( COREAUDIO_LIBS "-Wl,-framework,CoreAudio,-framework,AudioToolbox,-framework,AVFoundation" )
     endif ( COREAUDIO_FOUND )
     check_include_file ( CoreAudio/AudioHardware.h COREAUDIO_HAL_FOUND )
     if ( COREAUDIO_HAL_FOUND )

src/CMakeLists.txt

@@ -31,6 +31,9 @@ endif ( ALSA_SUPPORT )
 
 if ( COREAUDIO_SUPPORT )
   set ( fluid_coreaudio_SOURCES drivers/fluid_coreaudio.c )
+  if ( NOT COREAUDIO_SUPPORT_HAL )
+    set ( fluid_coreaudio_SOURCES ${fluid_coreaudio_SOURCES} drivers/fluid_coreaudio_avaudiosession.m )
+  endif ( COREAUDIO_SUPPORT_HAL )
 endif ( COREAUDIO_SUPPORT )
 
 if ( COREMIDI_SUPPORT )

src/drivers/fluid_coreaudio.c

@@ -38,9 +38,13 @@
 #include <CoreAudio/CoreAudioTypes.h>
 #if COREAUDIO_SUPPORT_HAL
 #include <CoreAudio/AudioHardware.h>
+#else
+#include "fluid_coreaudio_avaudiosession.h"
 #endif
 #include <AudioUnit/AudioUnit.h>
 
+const char PERF_MODE[] = "audio.coreaudio.performance-mode";
+
 /*
  * fluid_core_audio_driver_t
  *
@@ -204,6 +208,12 @@ fluid_core_audio_driver_settings(fluid_settings_t *settings)
     fluid_settings_register_str(settings, "audio.coreaudio.channel-map", "", 0);
     fluid_settings_add_option(settings, "audio.coreaudio.device", "default");
 
+#if !COREAUDIO_SUPPORT_HAL
+    fluid_settings_register_str(settings, PERF_MODE, "None", 0);
+    fluid_settings_add_option(settings, PERF_MODE, "None");
+    fluid_settings_add_option(settings, PERF_MODE, "LowLatency");
+#endif
+
 #if COREAUDIO_SUPPORT_HAL
     if(OK(AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &pa, 0, 0, &size)))
     {
@@ -251,6 +261,10 @@ new_fluid_core_audio_driver2(fluid_settings_t *settings, fluid_audio_func_t func
 #if COREAUDIO_SUPPORT_HAL
     char *devname = NULL;
     int i;
+#else
+    int avsession_ok;
+    int performance_mode;
+    char avaudiosession_msg[128] = "";
 #endif
     char *channel_map = NULL;
     fluid_core_audio_driver_t *dev = NULL;
@@ -386,7 +400,24 @@ new_fluid_core_audio_driver2(fluid_settings_t *settings, fluid_audio_func_t func
         }
     }
     FLUID_FREE(devname);  /* free device name */
-#endif
+
+#else /* COREAUDIO_SUPPORT_HAL */
+    performance_mode = fluid_settings_str_equal(settings, PERF_MODE, "LowLatency")
+                           ? AVAUDIOSESSION_MODE_LOW_LATENCY : AVAUDIOSESSION_MODE_NONE;
+
+    avsession_ok = setupAVAudioSession(performance_mode, period_size, sample_rate,
+                                       avaudiosession_msg, sizeof(avaudiosession_msg));
+
+    if (avaudiosession_msg[0] != 0) {
+        if (avsession_ok) {
+            FLUID_LOG(FLUID_INFO, "%s", avaudiosession_msg);
+        }
+        else {
+            FLUID_LOG(FLUID_ERR, "%s", avaudiosession_msg);
+        }
+    }
+#endif /* !COREAUDIO_SUPPORT_HAL */
+
 
 
     dev->buffer_size = period_size * periods;

src/drivers/fluid_coreaudio_avaudiosession.h

@@ -0,0 +1,20 @@
+#ifndef FLUID_COREAUDIO_AVAUDIOSESSION_H
+#define FLUID_COREAUDIO_AVAUDIOSESSION_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* PowerSaving mode is not yet supported, but in oboe driver,
+   PowerSaving mode is 1, so we leave LowLatency as 2,
+   for consistency with fluid_oboe.c */
+#define AVAUDIOSESSION_MODE_NONE 0
+#define AVAUDIOSESSION_MODE_LOW_LATENCY 2
+
+int setupAVAudioSession(int mode, int period_size, double sample_rate, char* msgbuf, int msgbufsize);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* FLUID_COREAUDIO_AVAUDIOSESSION_H */

src/drivers/fluid_coreaudio_avaudiosession.m

@@ -0,0 +1,77 @@
+#import <unistd.h>
+#import <AVFoundation/AVFoundation.h>
+#import "fluid_coreaudio_avaudiosession.h"
+
+void renderError(NSError* error, const char* desc, char* msgbuf, int msgbufsize) {
+    if (error != nil) {
+        snprintf(msgbuf, msgbufsize, "Error %s for low-latency audio session: %s",
+                 desc, error.description.UTF8String);
+    }
+    else {
+        snprintf(msgbuf, msgbufsize, "%s", desc);
+    }
+}
+
+int setupAVAudioSession(int mode, int period_size, double sample_rate, char* msgbuf, int msgbufsize) {
+    NSError *error = nil;
+    BOOL success = false;
+    NSTimeInterval bufDuration;
+    NSTimeInterval periodDuration;
+    NSString *category;
+    NSUInteger options;
+
+    AVAudioSession *session = [AVAudioSession sharedInstance];
+
+    if (mode == AVAUDIOSESSION_MODE_LOW_LATENCY) {
+        category = AVAudioSessionCategoryPlayAndRecord;
+    }
+    else {
+        category = AVAudioSessionCategoryPlayback;
+    }
+    options = AVAudioSessionCategoryOptionMixWithOthers | AVAudioSessionCategoryOptionDefaultToSpeaker;
+
+    success = [session setCategory:category withOptions:options error:&error];
+    if (!success) {
+        renderError(error, "setting audio session category", msgbuf, msgbufsize);
+        return 0;
+    }
+
+    success = [session setMode:AVAudioSessionModeDefault error:&error];
+    if (!success) {
+        renderError(error, "setting audio session mode", msgbuf, msgbufsize);
+        return 0;
+    }
+
+    success = [session setActive:YES error:&error];
+    if (!success) {
+        renderError(error, "activating audio session", msgbuf, msgbufsize);
+        return 0;
+    }
+
+    if (mode != AVAUDIOSESSION_MODE_LOW_LATENCY) {
+        snprintf(msgbuf, msgbufsize, "setupAVAudioSession: success");
+    }
+    else {
+        periodDuration = (double)period_size / sample_rate;
+        if (periodDuration == 0.0) {
+            periodDuration = 0.001;
+        }
+        bufDuration = periodDuration;
+
+        while (session.IOBufferDuration > bufDuration) {
+            success = [session setPreferredIOBufferDuration:bufDuration error:&error];
+
+            if (!success) {
+                renderError(error, "setting preferred I/O buffer duration", msgbuf, msgbufsize);
+                return 0;
+            }
+
+            bufDuration += periodDuration;
+        }
+
+        snprintf(msgbuf, msgbufsize, "setupAVAudioSession for low latency: success, io buffer duration = %f seconds",
+                 session.IOBufferDuration);
+    }
+
+    return 1;
+}