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audio: Offer a hint for libsamplerate quality/speed tradeoff.

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This defaults to the internal SDL resampler, since that's the likely default
without a system-wide install of libsamplerate, but those that need more can
tweak this.
This commit is contained in:
Ryan C. Gordon 2017-01-24 15:52:22 -05:00
parent 5ea0c893cd
commit c7f9dcb6fc
4 changed files with 57 additions and 4 deletions
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22
src/audio/SDL_audio.c
View file

@ -113,6 +113,7 @@ static const AudioBootStrap *const bootstrap[] = {
static void *SRC_lib = NULL;
#endif
SDL_bool SRC_available = SDL_FALSE;
int SRC_converter = 0;
SRC_STATE* (*SRC_src_new)(int converter_type, int channels, int *error) = NULL;
int (*SRC_src_process)(SRC_STATE *state, SRC_DATA *data) = NULL;
int (*SRC_src_reset)(SRC_STATE *state) = NULL;
@ -122,10 +123,25 @@ const char* (*SRC_src_strerror)(int error) = NULL;
static SDL_bool
LoadLibSampleRate(void)
{
SRC_available = SDL_FALSE;
const char *hint = SDL_GetHint(SDL_HINT_AUDIO_RESAMPLER_MODE);
if (!SDL_GetHintBoolean("SDL_AUDIO_ALLOW_LIBRESAMPLE", SDL_TRUE)) {
return SDL_FALSE;
SRC_available = SDL_FALSE;
SRC_converter = 0;
if (!hint || (SDL_strcasecmp(hint, "default") == 0)) {
return SDL_FALSE; /* don't load anything. */
} else if (SDL_strcasecmp(hint, "linear") == 0) {
SRC_converter = SRC_LINEAR;
} else if (SDL_strcasecmp(hint, "zero_order_hold") == 0) {
SRC_converter = SRC_ZERO_ORDER_HOLD;
} else if (SDL_strcasecmp(hint, "sinc_fastest") == 0) {
SRC_converter = SRC_SINC_FASTEST;
} else if (SDL_strcasecmp(hint, "sinc_medium") == 0) {
SRC_converter = SRC_SINC_MEDIUM_QUALITY;
} else if (SDL_strcasecmp(hint, "sinc_best") == 0) {
SRC_converter = SRC_SINC_BEST_QUALITY;
} else {
return SDL_FALSE; /* treat it like "default", don't load anything. */
}
#ifdef SDL_LIBSAMPLERATE_DYNAMIC

1
src/audio/SDL_audio_c.h
View file

@ -39,6 +39,7 @@
#ifdef HAVE_LIBSAMPLERATE_H
#include "samplerate.h"
extern SDL_bool SRC_available;
extern int SRC_converter;
extern SRC_STATE* (*SRC_src_new)(int converter_type, int channels, int *error);
extern int (*SRC_src_process)(SRC_STATE *state, SRC_DATA *data);
extern int (*SRC_src_reset)(SRC_STATE *state);

2
src/audio/SDL_audiocvt.c
View file

@ -947,7 +947,7 @@ SetupLibSampleRateResampling(SDL_AudioStream *stream)
SRC_STATE *state = NULL;
if (SRC_available) {
state = SRC_src_new(SRC_SINC_FASTEST, stream->pre_resample_channels, &result);
state = SRC_src_new(SRC_converter, stream->pre_resample_channels, &result);
if (!state) {
SDL_SetError("src_new() failed: %s", SRC_src_strerror(result));
}