From 20bd7c111b3271abd894b7a43eb3d4a5b21922c1 Mon Sep 17 00:00:00 2001 From: jdgleaver Date: Mon, 29 Nov 2021 17:45:06 +0000 Subject: [PATCH] Calculate number of audio samples to read per frame deterministically --- libretro/libretro.c | 92 +++++++++++++++++++-------------------------- sound.c | 29 +++++++------- sound.h | 3 +- 3 files changed, 55 insertions(+), 69 deletions(-) diff --git a/libretro/libretro.c b/libretro/libretro.c index 0c02e05..a908dec 100644 --- a/libretro/libretro.c +++ b/libretro/libretro.c @@ -54,13 +54,9 @@ static int translation_caches_inited = 0; // Usually 59.72750057 Hz, unless GBC_RATE is overclocked (for 60FPS) #define GBA_FPS ((float) GBC_BASE_RATE) / (308 * 228 * 4) -/* An alpha factor of 1/180 is *somewhat* equivalent - * to calculating the average for the last 180 - * frames, or 3 seconds of runtime... */ -#define SAMPLES_PER_FRAME_MOVING_AVG_ALPHA (1.0f / 180.0f) -static s16 *audio_sample_buffer = NULL; -static u32 audio_sample_buffer_size = 0; -static float audio_samples_per_frame_avg = 0.0f; +static s16 *audio_sample_buffer = NULL; +static float audio_samples_per_frame = 0.0f; +static float audio_samples_accumulator = 0.0f; /* Workaround for a RetroArch audio driver * limitation: a maximum of 1024 frames @@ -383,51 +379,40 @@ void set_fastforward_override(bool fastforward) static void audio_run(void) { - u32 samples_available = sound_samples_available(); + s16 *audio_buffer_ptr; + u32 samples_to_read; + u32 samples_produced; - if (samples_available > 0) + /* audio_samples_per_frame is decimal; + * get integer component */ + samples_to_read = (u32)audio_samples_per_frame; + + /* Account for fractional component */ + audio_samples_accumulator += audio_samples_per_frame - + (float)samples_to_read; + + if (audio_samples_accumulator >= 1.0f) { - s16 *audio_buffer_ptr; - u32 samples_to_read; - u32 samples_produced; + samples_to_read++; + audio_samples_accumulator -= 1.0f; + } - /* Update 'running average' of number of - * samples per frame. - * Note that this is not a true running - * average, but just a leaky-integrator/ - * exponential moving average, used because - * it is simple and fast (i.e. requires no - * window of samples). */ - audio_samples_per_frame_avg = (SAMPLES_PER_FRAME_MOVING_AVG_ALPHA * (float)samples_available) + - ((1.0f - SAMPLES_PER_FRAME_MOVING_AVG_ALPHA) * audio_samples_per_frame_avg); + samples_produced = sound_read_samples(audio_sample_buffer, samples_to_read); - samples_to_read = (u32)(audio_samples_per_frame_avg + 0.5f); + /* Workaround for a RetroArch audio driver + * limitation: a maximum of 1024 frames + * can be written per call of audio_batch_cb(), + * so we have to send samples in chunks */ + audio_buffer_ptr = audio_sample_buffer; + while (samples_produced > 0) + { + u32 samples_to_write = (samples_produced > AUDIO_BATCH_FRAMES_MAX) ? + AUDIO_BATCH_FRAMES_MAX : samples_produced; - /* Resize audio output buffer, if required */ - if (audio_sample_buffer_size < (samples_to_read * 2)) - { - audio_sample_buffer_size = (samples_to_read * 2); - audio_sample_buffer = (s16*)realloc(audio_sample_buffer, - audio_sample_buffer_size * sizeof(s16)); - } + audio_batch_cb(audio_buffer_ptr, samples_to_write); - samples_produced = sound_read_samples(audio_sample_buffer, samples_to_read); - - /* Workaround for a RetroArch audio driver - * limitation: a maximum of 1024 frames - * can be written per call of audio_batch_cb(), - * so we have to send samples in chunks */ - audio_buffer_ptr = audio_sample_buffer; - while (samples_produced > 0) - { - u32 samples_to_write = (samples_produced > AUDIO_BATCH_FRAMES_MAX) ? - AUDIO_BATCH_FRAMES_MAX : samples_produced; - - audio_batch_cb(audio_buffer_ptr, samples_to_write); - - samples_produced -= samples_to_write; - audio_buffer_ptr += samples_to_write << 1; - } + samples_produced -= samples_to_write; + audio_buffer_ptr += samples_to_write << 1; } } @@ -521,10 +506,11 @@ void retro_get_system_av_info(struct retro_system_av_info* info) void retro_init(void) { - u32 audio_samples_per_frame = (u32)((float)(GBA_SOUND_FREQUENCY) / (float)(GBA_FPS)); - audio_sample_buffer_size = audio_samples_per_frame * 2; - audio_sample_buffer = (s16*)malloc(audio_sample_buffer_size * sizeof(s16)); - audio_samples_per_frame_avg = (float)audio_samples_per_frame; + u32 audio_sample_buffer_size; + audio_samples_per_frame = (float)(GBA_SOUND_FREQUENCY) / (float)(GBA_FPS); + audio_samples_accumulator = 0.0f; + audio_sample_buffer_size = ((u32)audio_samples_per_frame + 1) * 2; + audio_sample_buffer = (s16*)malloc(audio_sample_buffer_size * sizeof(s16)); #if defined(HAVE_DYNAREC) #if defined(MMAP_JIT_CACHE) @@ -666,9 +652,9 @@ void retro_deinit(void) if (audio_sample_buffer) free(audio_sample_buffer); - audio_sample_buffer = NULL; - audio_sample_buffer_size = 0; - audio_samples_per_frame_avg = 0.0f; + audio_sample_buffer = NULL; + audio_samples_per_frame = 0.0f; + audio_samples_accumulator = 0.0f; } static retro_time_t retro_perf_dummy_get_time_usec() { return 0; } diff --git a/sound.c b/sound.c index e50bf0a..a99c9b2 100644 --- a/sound.c +++ b/sound.c @@ -749,22 +749,22 @@ unsigned sound_write_savestate(u8 *dst) return (unsigned int)(dst - startp); } -u32 sound_samples_available(void) +u32 sound_read_samples(s16 *out, u32 frames) { - u32 num_samples = (gbc_sound_buffer_index - sound_buffer_base) & BUFFER_SIZE_MASK; - num_samples = (num_samples > 512) ? (num_samples - 512) : 0; - return (num_samples >> 1); -} - -u32 sound_read_samples(s16 *out, u32 count) -{ - u32 samples_available = sound_samples_available(); u32 i; + u32 samples_to_read = frames << 1; + /* Get total number of samples in the buffer */ + u32 samples_available = (gbc_sound_buffer_index - sound_buffer_base) & BUFFER_SIZE_MASK; + /* The last 512 samples are 'in use', and cannot + * be read out yet */ + samples_available = (samples_available > 512) ? (samples_available - 512) : 0; + /* Available sample count must be an even number */ + samples_available = (samples_available >> 1) << 1; - if (count > samples_available) - count = samples_available; + if (samples_to_read > samples_available) + samples_to_read = samples_available; - for(i = 0; i < (count << 1); i++) + for(i = 0; i < samples_to_read; i++) { u32 source_index = (sound_buffer_base + i) & BUFFER_SIZE_MASK; s32 current_sample = sound_buffer[source_index]; @@ -779,8 +779,9 @@ u32 sound_read_samples(s16 *out, u32 count) out[i] = current_sample * 16; } - sound_buffer_base += (count << 1); + sound_buffer_base += samples_to_read; sound_buffer_base &= BUFFER_SIZE_MASK; - return count; + /* Function returns number of frames read */ + return (samples_to_read >> 1); } diff --git a/sound.h b/sound.h index 1bdcf59..28076dc 100644 --- a/sound.h +++ b/sound.h @@ -108,8 +108,7 @@ void init_sound(int need_reset); unsigned sound_write_savestate(u8 *dst); bool sound_read_savestate(const u8 *src); -u32 sound_samples_available(void); -u32 sound_read_samples(s16 *out, u32 count); +u32 sound_read_samples(s16 *out, u32 frames); void reset_sound(void);