alsa: set period size before buffer size. make it match SAMPLE_COUNT

simplify WriteSample

core/oslib/audiobackend_alsa.cpp

@@ -111,6 +111,16 @@ static void alsa_init()
 		return;
 	}
 
+	// Period size (512)
+	period_size = std::min(SAMPLE_COUNT, (u32)config::AudioBufferSize / 4);
+	rc = snd_pcm_hw_params_set_period_size_near(handle, params, &period_size, nullptr);
+	if (rc < 0)
+	{
+		WARN_LOG(AUDIO, "ALSA: Error:snd_pcm_hw_params_set_periods_near %s", snd_strerror(rc));
+		return;
+	}
+	INFO_LOG(AUDIO, "ALSA: period size set to %zd", (size_t)period_size);
+
 	// Sample buffer size
 	buffer_size = config::AudioBufferSize;
 	rc = snd_pcm_hw_params_set_buffer_size_near(handle, params, &buffer_size);
@@ -121,16 +131,6 @@ static void alsa_init()
 	}
 	INFO_LOG(AUDIO, "ALSA: buffer size set to %ld", buffer_size);
 
-	// Period size (1024)
-	period_size = 1024;
-	rc = snd_pcm_hw_params_set_period_size_near(handle, params, &period_size, nullptr);
-	if (rc < 0)
-	{
-		WARN_LOG(AUDIO, "ALSA: Error:snd_pcm_hw_params_set_periods_near %s", snd_strerror(rc));
-		return;
-	}
-	INFO_LOG(AUDIO, "ALSA: period size set to %zd", (size_t)period_size);
-
 	/* Write the parameters to the driver */
 	rc = snd_pcm_hw_params(handle, params);
 	if (rc < 0)
@@ -241,16 +241,19 @@ static u32 alsa_push(const void* frame, u32 samples, bool wait)
 	}
 
 	int rc = snd_pcm_writei(handle, frame, samples);
-	if (rc == -EPIPE)
+	if (rc < 0)
 	{
-		/* EPIPE means underrun */
-		snd_pcm_prepare(handle);
-		// Write some silence then our samples
-		const size_t silence_size = buffer_size - period_size;
-		void *silence = alloca(silence_size * 4);
-		memset(silence, 0, silence_size * 4);
-		snd_pcm_writei(handle, silence, silence_size);
-		snd_pcm_writei(handle, frame, samples);
+		snd_pcm_recover(handle, rc, 1);
+		if (rc == -EPIPE)
+		{
+			// EPIPE means underrun
+			// Write some silence then our samples
+			const size_t silence_size = buffer_size - samples;
+			void *silence = alloca(silence_size * 4);
+			memset(silence, 0, silence_size * 4);
+			snd_pcm_writei(handle, silence, silence_size);
+			snd_pcm_writei(handle, frame, samples);
+		}
 	}
 	return 1;
 }

core/oslib/audiostream.cpp

@@ -1,14 +1,10 @@
 #include "audiostream.h"
-
-#include <algorithm>
 #include <memory>
 
-struct SoundFrame { s16 l;s16 r; };
-constexpr u32 SAMPLE_COUNT =  512;
+struct SoundFrame { s16 l; s16 r; };
 
-static SoundFrame RingBuffer[SAMPLE_COUNT];
-
-static u32 WritePtr;  //last WRITTEN sample
+static SoundFrame Buffer[SAMPLE_COUNT];
+static u32 writePtr;  // next sample index
 
 static audiobackend_t *audiobackend_current = nullptr;
 static std::unique_ptr<std::vector<audiobackend_t *>> audiobackends;	// Using a pointer to avoid out of order init
@@ -81,23 +77,17 @@ audiobackend_t* GetAudioBackend(const std::string& slug)
 	return nullptr;
 }
 
-static u32 PushAudio(void* frame, u32 amt, bool wait)
-{
-	if (audiobackend_current != nullptr)
-		return audiobackend_current->push(frame, amt, wait);
-
-	return 0;
-}
-
 void WriteSample(s16 r, s16 l)
 {
-	const u32 ptr=(WritePtr+1)%SAMPLE_COUNT;
-	RingBuffer[ptr].r=r;
-	RingBuffer[ptr].l=l;
-	WritePtr=ptr;
+	Buffer[writePtr].r = r;
+	Buffer[writePtr].l = l;
 
-	if (WritePtr == SAMPLE_COUNT - 1)
-		PushAudio(RingBuffer,SAMPLE_COUNT, config::LimitFPS);
+	if (++writePtr == SAMPLE_COUNT)
+	{
+		if (audiobackend_current != nullptr)
+			audiobackend_current->push(Buffer, SAMPLE_COUNT, config::LimitFPS);
+		writePtr = 0;
+	}
 }
 
 void InitAudio()

core/oslib/audiostream.h

@@ -26,7 +26,7 @@ typedef struct {
 typedef audio_option_t* (*audio_options_func_t)(int* option_count);
 
 typedef void (*audio_backend_init_func_t)();
-typedef u32 (*audio_backend_push_func_t)(const void*, u32, bool);
+typedef u32 (*audio_backend_push_func_t)(const void *data, u32 frames, bool wait);
 typedef void (*audio_backend_term_func_t)();
 typedef struct {
     std::string slug;
@@ -51,3 +51,5 @@ void StopAudioRecording();
 u32 GetAudioBackendCount();
 audiobackend_t* GetAudioBackend(int num);
 audiobackend_t* GetAudioBackend(const std::string& slug);
+
+constexpr u32 SAMPLE_COUNT = 512;	// push() is always called with that many frames

shell/android-studio/reicast/src/main/jni/src/Android.cpp

@@ -291,7 +291,6 @@ jmethodID startRecordingMid;
 jmethodID stopRecordingMid;
 
 //stuff for audio
-#define SAMPLE_COUNT 512
 jshortArray jsamples;
 jmethodID writeBufferMid;
 jmethodID audioInitMid;
@@ -468,7 +467,6 @@ JNIEXPORT jboolean JNICALL Java_com_reicast_emulator_emu_JNIdc_guiIsContentBrows
 // Audio Stuff
 static u32 androidaudio_push(const void* frame, u32 amt, bool wait)
 {
-    verify(amt==SAMPLE_COUNT);
     jvm_attacher.getEnv()->SetShortArrayRegion(jsamples, 0, amt * 2, (jshort *)frame);
     return jvm_attacher.getEnv()->CallIntMethod(g_audioBackend, writeBufferMid, jsamples, wait);
 }