- 根目录:
- sound
- core
- oss
- rate.c
/*
* Rate conversion Plug-In
* Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz>
*
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/time.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include "pcm_plugin.h"
#define SHIFT 11
#define BITS (1<<SHIFT)
#define R_MASK (BITS-1)
/*
* Basic rate conversion plugin
*/
struct rate_channel {
signed short last_S1;
signed short last_S2;
};
typedef void (*rate_f)(struct snd_pcm_plugin *plugin,
const struct snd_pcm_plugin_channel *src_channels,
struct snd_pcm_plugin_channel *dst_channels,
int src_frames, int dst_frames);
struct rate_priv {
unsigned int pitch;
unsigned int pos;
rate_f func;
snd_pcm_sframes_t old_src_frames, old_dst_frames;
struct rate_channel channels[0];
};
static void rate_init(struct snd_pcm_plugin *plugin)
{
unsigned int channel;
struct rate_priv *data = (struct rate_priv *)plugin->extra_data;
data->pos = 0;
for (channel = 0; channel < plugin->src_format.channels; channel++) {
data->channels[channel].last_S1 = 0;
data->channels[channel].last_S2 = 0;
}
}
static void resample_expand(struct snd_pcm_plugin *plugin,
const struct snd_pcm_plugin_channel *src_channels,
struct snd_pcm_plugin_channel *dst_channels,
int src_frames, int dst_frames)
{
unsigned int pos = 0;
signed int val;
signed short S1, S2;
signed short *src, *dst;
unsigned int channel;
int src_step, dst_step;
int src_frames1, dst_frames1;
struct rate_priv *data = (struct rate_priv *)plugin->extra_data;
struct rate_channel *rchannels = data->channels;
for (channel = 0; channel < plugin->src_format.channels; channel++) {
pos = data->pos;
S1 = rchannels->last_S1;
S2 = rchannels->last_S2;
if (!src_channels[channel].enabled) {
if (dst_channels[channel].wanted)
snd_pcm_area_silence(&dst_channels[channel].area, 0, dst_frames, plugin->dst_format.format);
dst_channels[channel].enabled = 0;
continue;
}
dst_channels[channel].enabled = 1;
src = (signed short *)src_channels[channel].area.addr +
src_channels[channel].area.first / 8 / 2;
dst = (signed short *)dst_channels[channel].area.addr +
dst_channels[channel].area.first / 8 / 2;
src_step = src_channels[channel].area.step / 8 / 2;
dst_step = dst_channels[channel].area.step / 8 / 2;
src_frames1 = src_frames;
dst_frames1 = dst_frames;
while (dst_frames1-- > 0) {
if (pos & ~R_MASK) {
pos &= R_MASK;
S1 = S2;
if (src_frames1-- > 0) {
S2 = *src;
src += src_step;
}
}
val = S1 + ((S2 - S1) * (signed int)pos) / BITS;
if (val < -32768)
val = -32768;
else if (val > 32767)
val = 32767;
*dst = val;
dst += dst_step;
pos += data->pitch;
}
rchannels->last_S1 = S1;
rchannels->last_S2 = S2;
rchannels++;
}
data->pos = pos;
}
static void resample_shrink(struct snd_pcm_plugin *plugin,
const struct snd_pcm_plugin_channel *src_channels,
struct snd_pcm_plugin_channel *dst_channels,
int src_frames, int dst_frames)
{
unsigned int pos = 0;
signed int val;
signed short S1, S2;
signed short *src, *dst;
unsigned int channel;
int src_step, dst_step;
int src_frames1, dst_frames1;
struct rate_priv *data = (struct rate_priv *)plugin->extra_data;
struct rate_channel *rchannels = data->channels;
for (channel = 0; channel < plugin->src_format.channels; ++channel) {
pos = data->pos;
S1 = rchannels->last_S1;
S2 = rchannels->last_S2;
if (!src_channels[channel].enabled) {
if (dst_channels[channel].wanted)
snd_pcm_area_silence(&dst_channels[channel].area, 0, dst_frames, plugin->dst_format.format);
dst_channels[channel].enabled = 0;
continue;
}
dst_channels[channel].enabled = 1;
src = (signed short *)src_channels[channel].area.addr +
src_channels[channel].area.first / 8 / 2;
dst = (signed short *)dst_channels[channel].area.addr +
dst_channels[channel].area.first / 8 / 2;
src_step = src_channels[channel].area.step / 8 / 2;
dst_step = dst_channels[channel].area.step / 8 / 2;
src_frames1 = src_frames;
dst_frames1 = dst_frames;
while (dst_frames1 > 0) {
S1 = S2;
if (src_frames1-- > 0) {
S2 = *src;
src += src_step;
}
if (pos & ~R_MASK) {
pos &= R_MASK;
val = S1 + ((S2 - S1) * (signed int)pos) / BITS;
if (val < -32768)
val = -32768;
else if (val > 32767)
val = 32767;
*dst = val;
dst += dst_step;
dst_frames1--;
}
pos += data->pitch;
}
rchannels->last_S1 = S1;
rchannels->last_S2 = S2;
rchannels++;
}
data->pos = pos;
}
static snd_pcm_sframes_t rate_src_frames(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t frames)
{
struct rate_priv *data;
snd_pcm_sframes_t res;
if (snd_BUG_ON(!plugin))
return -ENXIO;
if (frames == 0)
return 0;
data = (struct rate_priv *)plugin->extra_data;
if (plugin->src_format.rate < plugin->dst_format.rate) {
res = (((frames * data->pitch) + (BITS/2)) >> SHIFT);
} else {
res = (((frames << SHIFT) + (data->pitch / 2)) / data->pitch);
}
if (data->old_src_frames > 0) {
snd_pcm_sframes_t frames1 = frames, res1 = data->old_dst_frames;
while (data->old_src_frames < frames1) {
frames1 >>= 1;
res1 <<= 1;
}
while (data->old_src_frames > frames1) {
frames1 <<= 1;
res1 >>= 1;
}
if (data->old_src_frames == frames1)
return res1;
}
data->old_src_frames = frames;
data->old_dst_frames = res;
return res;
}
static snd_pcm_sframes_t rate_dst_frames(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t frames)
{
struct rate_priv *data;
snd_pcm_sframes_t res;
if (snd_BUG_ON(!plugin))
return -ENXIO;
if (frames == 0)
return 0;
data = (struct rate_priv *)plugin->extra_data;
if (plugin->src_format.rate < plugin->dst_format.rate) {
res = (((frames << SHIFT) + (data->pitch / 2)) / data->pitch);
} else {
res = (((frames * data->pitch) + (BITS/2)) >> SHIFT);
}
if (data->old_dst_frames > 0) {
snd_pcm_sframes_t frames1 = frames, res1 = data->old_src_frames;
while (data->old_dst_frames < frames1) {
frames1 >>= 1;
res1 <<= 1;
}
while (data->old_dst_frames > frames1) {
frames1 <<= 1;
res1 >>= 1;
}
if (data->old_dst_frames == frames1)
return res1;
}
data->old_dst_frames = frames;
data->old_src_frames = res;
return res;
}
static snd_pcm_sframes_t rate_transfer(struct snd_pcm_plugin *plugin,
const struct snd_pcm_plugin_channel *src_channels,
struct snd_pcm_plugin_channel *dst_channels,
snd_pcm_uframes_t frames)
{
snd_pcm_uframes_t dst_frames;
struct rate_priv *data;
if (snd_BUG_ON(!plugin || !src_channels || !dst_channels))
return -ENXIO;
if (frames == 0)
return 0;
#ifdef CONFIG_SND_DEBUG
{
unsigned int channel;
for (channel = 0; channel < plugin->src_format.channels; channel++) {
if (snd_BUG_ON(src_channels[channel].area.first % 8 ||
src_channels[channel].area.step % 8))
return -ENXIO;
if (snd_BUG_ON(dst_channels[channel].area.first % 8 ||
dst_channels[channel].area.step % 8))
return -ENXIO;
}
}
#endif
dst_frames = rate_dst_frames(plugin, frames);
if (dst_frames > dst_channels[0].frames)
dst_frames = dst_channels[0].frames;
data = (struct rate_priv *)plugin->extra_data;
data->func(plugin, src_channels, dst_channels, frames, dst_frames);
return dst_frames;
}
static int rate_action(struct snd_pcm_plugin *plugin,
enum snd_pcm_plugin_action action,
unsigned long udata)
{
if (snd_BUG_ON(!plugin))
return -ENXIO;
switch (action) {
case INIT:
case PREPARE:
rate_init(plugin);
break;
default:
break;
}
return 0; /* silenty ignore other actions */
}
int snd_pcm_plugin_build_rate(struct snd_pcm_substream *plug,
struct snd_pcm_plugin_format *src_format,
struct snd_pcm_plugin_format *dst_format,
struct snd_pcm_plugin **r_plugin)
{
int err;
struct rate_priv *data;
struct snd_pcm_plugin *plugin;
if (snd_BUG_ON(!r_plugin))
return -ENXIO;
*r_plugin = NULL;
if (snd_BUG_ON(src_format->channels != dst_format->channels))
return -ENXIO;
if (snd_BUG_ON(src_format->channels <= 0))
return -ENXIO;
if (snd_BUG_ON(src_format->format != SNDRV_PCM_FORMAT_S16))
return -ENXIO;
if (snd_BUG_ON(dst_format->format != SNDRV_PCM_FORMAT_S16))
return -ENXIO;
if (snd_BUG_ON(src_format->rate == dst_format->rate))
return -ENXIO;
err = snd_pcm_plugin_build(plug, "rate conversion",
src_format, dst_format,
sizeof(struct rate_priv) +
src_format->channels * sizeof(struct rate_channel),
&plugin);
if (err < 0)
return err;
data = (struct rate_priv *)plugin->extra_data;
if (src_format->rate < dst_format->rate) {
data->pitch = ((src_format->rate << SHIFT) + (dst_format->rate >> 1)) / dst_format->rate;
data->func = resample_expand;
} else {
data->pitch = ((dst_format->rate << SHIFT) + (src_format->rate >> 1)) / src_format->rate;
data->func = resample_shrink;
}
data->pos = 0;
rate_init(plugin);
data->old_src_frames = data->old_dst_frames = 0;
plugin->transfer = rate_transfer;
plugin->src_frames = rate_src_frames;
plugin->dst_frames = rate_dst_frames;
plugin->action = rate_action;
*r_plugin = plugin;
return 0;
}