Corrections to audio buffer size calculations

2 files changed, 14 insertions, 6 deletions

diff --git a/drivers/alsa/audio_driver_alsa.cpp b/drivers/alsa/audio_driver_alsa.cpp
index 40c66b0bc5..216100bac6 100644
--- a/drivers/alsa/audio_driver_alsa.cpp
+++ b/drivers/alsa/audio_driver_alsa.cpp
@@ -31,6 +31,7 @@
 
 #ifdef ALSA_ENABLED
 
+#include "os/os.h"
 #include "project_settings.h"
 
 #include <errno.h>
@@ -44,7 +45,7 @@ Error AudioDriverALSA::init() {
 	samples_in = NULL;
 	samples_out = NULL;
 
-	mix_rate = GLOBAL_DEF("audio/mix_rate", 44100);
+	mix_rate = GLOBAL_DEF("audio/mix_rate", DEFAULT_MIX_RATE);
 	speaker_mode = SPEAKER_MODE_STEREO;
 	channels = 2;
 
@@ -86,19 +87,25 @@ Error AudioDriverALSA::init() {
 	status = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &mix_rate, NULL);
 	CHECK_FAIL(status < 0);
 
-	int latency = GLOBAL_DEF("audio/output_latency", 25);
-	buffer_size = closest_power_of_2(latency * mix_rate / 1000);
+	// In ALSA the period size seems to be the one that will determine the actual latency
+	// Ref: https://www.alsa-project.org/main/index.php/FramesPeriods
+	unsigned int periods = 2;
+	int latency = GLOBAL_DEF("audio/output_latency", DEFAULT_OUTPUT_LATENCY);
+	buffer_frames = closest_power_of_2(latency * mix_rate / 1000);
+	buffer_size = buffer_frames * periods;
+	period_size = buffer_frames;
 
 	// set buffer size from project settings
 	status = snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hwparams, &buffer_size);
 	CHECK_FAIL(status < 0);
 
-	// make period size 1/8
-	period_size = buffer_size >> 3;
 	status = snd_pcm_hw_params_set_period_size_near(pcm_handle, hwparams, &period_size, NULL);
 	CHECK_FAIL(status < 0);
 
-	unsigned int periods = 2;
+	if (OS::get_singleton()->is_stdout_verbose()) {
+		print_line("audio buffer frames: " + itos(period_size) + " calculated latency: " + itos(period_size * 1000 / mix_rate) + "ms");
+	}
+
 	status = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &periods, NULL);
 	CHECK_FAIL(status < 0);
 
diff --git a/drivers/alsa/audio_driver_alsa.h b/drivers/alsa/audio_driver_alsa.h
index 83601be41b..c76ec0da61 100644
--- a/drivers/alsa/audio_driver_alsa.h
+++ b/drivers/alsa/audio_driver_alsa.h
@@ -51,6 +51,7 @@ class AudioDriverALSA : public AudioDriver {
 	unsigned int mix_rate;
 	SpeakerMode speaker_mode;
 
+	snd_pcm_uframes_t buffer_frames;
 	snd_pcm_uframes_t buffer_size;
 	snd_pcm_uframes_t period_size;
 	int channels;