mirrors/alsa-lib
1
0
Fork 0
mirror of https://github.com/alsa-project/alsa-lib.git synced 2025-10-29 05:40:25 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

Cleanups in expand()

Browse source
This commit is contained in:
Jaroslav Kysela 2002-03-11 18:56:34 +00:00
parent ff5535a285
commit 76712fb46b
1 changed files with 23 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

34
src/pcm/pcm_rate.c
View file

@ -42,7 +42,7 @@ const char *_snd_module_pcm_rate = "";
typedef struct {
int init;
int16_t sample;
int16_t old_sample, new_sample;
int sum;
unsigned int pos;
} snd_pcm_rate_state_t;
@ -117,7 +117,8 @@ static snd_pcm_uframes_t snd_pcm_rate_expand(const snd_pcm_channel_area_t *dst_a
const char *src;
char *dst;
int src_step, dst_step;
int16_t old_sample = states->sample;
int16_t old_sample = states->old_sample;
int16_t new_sample = states->new_sample;
unsigned int pos = states->pos;
src = snd_pcm_channel_area_addr(src_area, src_offset);
dst = snd_pcm_channel_area_addr(dst_area, dst_offset);
@ -126,27 +127,36 @@ static snd_pcm_uframes_t snd_pcm_rate_expand(const snd_pcm_channel_area_t *dst_a
src_frames1 = 0;
dst_frames1 = 0;
if (states->init) {
old_sample = initial_sample(src, getidx);
new_sample = initial_sample(src, getidx);
src_frames1++;
states->init = 0;
}
while (dst_frames1 < dst_frames) {
if (pos >= get_threshold) {
int16_t new_sample;
if (src_frames1 == src_frames)
break;
old_sample = new_sample;
pos -= get_threshold;
goto *get;
#define GET16_END after_get
#include "plugin_ops.h"
#undef GET16_END
after_get:
new_sample = sample;
src += src_step;
src_frames1++;
new_sample = sample;
sample = (old_sample * (DIV - pos) + new_sample * pos) / DIV;
old_sample = new_sample;
} else
sample = old_sample;
#if 1 /* fast-change interpolation */
/* this interpolation gives us better results especially for low-rate sources */
// sample = (((int)old_sample * (DIV - pos)) + ((int)new_sample * pos)) / DIV;
sample = ((int)old_sample + (int)new_sample) / 2;
} else {
sample = new_sample;
}
#else /* linear interpolation */
/* in some cases, a high-band filter is required to remove high noises */
}
sample = (((int)old_sample * (DIV - pos)) + ((int)new_sample * pos)) / DIV;
#endif
goto *put;
#define PUT16_END after_put
#include "plugin_ops.h"
@ -156,7 +166,8 @@ static snd_pcm_uframes_t snd_pcm_rate_expand(const snd_pcm_channel_area_t *dst_a
dst_frames1++;
pos += DIV;
}
states->sample = old_sample;
states->old_sample = old_sample;
states->new_sample = new_sample;
states->pos = pos;
states++;
}
@ -447,7 +458,8 @@ static int snd_pcm_rate_init(snd_pcm_t *pcm)
unsigned int k;
for (k = 0; k < pcm->channels; ++k) {
rate->states[k].sum = 0;
rate->states[k].sample = 0;
rate->states[k].old_sample = 0;
rate->states[k].new_sample = 0;
rate->states[k].pos = 0;
rate->states[k].init = 0;
}