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Fixed bug 5080 - SDL_netbsdaudio: Always use the device's preferred frequency 

Nia Alarie

The NetBSD kernel's audio resampling code is much simpler and lower quality than libsamplerate.

Presumably, if SDL always performs I/O on the audio device in its native frequency, we can avoid resampling audio in the kernel and let SDL do it with libsamplerate instead.
This commit is contained in:
Sam Lantinga 2021-01-08 10:09:37 -08:00
parent 2f72535c62
commit 50ea3b77f1
1 changed files with 19 additions and 10 deletions
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29
src/audio/netbsd/SDL_netbsdaudio.c
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@ -205,7 +205,7 @@ static int
NETBSDAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
{
SDL_AudioFormat format = 0;
audio_info_t info;
audio_info_t info, hwinfo;
struct audio_prinfo *prinfo = iscapture ? &info.record : &info.play;
/* We don't care what the devname is...we'll try to open anything. */
@ -233,7 +233,20 @@ NETBSDAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
AUDIO_INITINFO(&info);
#ifdef AUDIO_GETFORMAT /* Introduced in NetBSD 9.0 */
if (ioctl(this->hidden->audio_fd, AUDIO_GETFORMAT, &hwinfo) != -1) {
/*
* Use the device's native sample rate so the kernel doesn't have to
* resample.
*/
this->spec.freq = iscapture ?
hwinfo.record.sample_rate : hwinfo.play.sample_rate;
}
#endif
prinfo->encoding = AUDIO_ENCODING_NONE;
prinfo->sample_rate = this->spec.freq;
prinfo->channels = this->spec.channels;
for (format = SDL_FirstAudioFormat(this->spec.format); format;) {
switch (format) {
@ -280,23 +293,19 @@ NETBSDAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
return SDL_SetError("No supported encoding for 0x%x", this->spec.format);
}
this->spec.format = format;
/* Calculate spec parameters based on our chosen format */
SDL_CalculateAudioSpec(&this->spec);
info.mode = iscapture ? AUMODE_RECORD : AUMODE_PLAY;
info.blocksize = this->spec.size;
info.hiwat = 5;
info.lowat = 3;
prinfo->sample_rate = this->spec.freq;
prinfo->channels = this->spec.channels;
(void) ioctl(this->hidden->audio_fd, AUDIO_SETINFO, &info);
(void) ioctl(this->hidden->audio_fd, AUDIO_GETINFO, &info);
/* Final spec used for the device. */
this->spec.format = format;
this->spec.freq = prinfo->sample_rate;
this->spec.channels = prinfo->channels;
SDL_CalculateAudioSpec(&this->spec);
if (!iscapture) {
/* Allocate mixing buffer */
this->hidden->mixlen = this->spec.size;