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linux-stable/sound/core/oss/rate.c
Steve Chen 5370d96f85 ALSA: fix excessive background noise introduced by OSS emulation rate shrink 
Incorrect variable was used to get the next sample which caused S2
to be stuck with the same value resulting in loud background noise.

Signed-off-by: Steve Chen <schen at mvista.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2009-02-23 07:49:04 +01:00

348 lines
9.7 KiB
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/*
* 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;
}
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