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rate.c
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1 /*
2  * Rate conversion Plug-In
3  * Copyright (c) 1999 by Jaroslav Kysela <[email protected]>
4  *
5  *
6  * This library is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU Library General Public License as
8  * published by the Free Software Foundation; either version 2 of
9  * the License, or (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU Library General Public License for more details.
15  *
16  * You should have received a copy of the GNU Library General Public
17  * License along with this library; if not, write to the Free Software
18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19  *
20  */
21 
22 #include <linux/time.h>
23 #include <sound/core.h>
24 #include <sound/pcm.h>
25 #include "pcm_plugin.h"
26 
27 #define SHIFT 11
28 #define BITS (1<<SHIFT)
29 #define R_MASK (BITS-1)
30 
31 /*
32  * Basic rate conversion plugin
33  */
34 
35 struct rate_channel {
36  signed short last_S1;
37  signed short last_S2;
38 };
39 
40 typedef void (*rate_f)(struct snd_pcm_plugin *plugin,
41  const struct snd_pcm_plugin_channel *src_channels,
42  struct snd_pcm_plugin_channel *dst_channels,
43  int src_frames, int dst_frames);
44 
45 struct rate_priv {
46  unsigned int pitch;
47  unsigned int pos;
48  rate_f func;
49  snd_pcm_sframes_t old_src_frames, old_dst_frames;
50  struct rate_channel channels[0];
51 };
52 
53 static void rate_init(struct snd_pcm_plugin *plugin)
54 {
55  unsigned int channel;
56  struct rate_priv *data = (struct rate_priv *)plugin->extra_data;
57  data->pos = 0;
58  for (channel = 0; channel < plugin->src_format.channels; channel++) {
59  data->channels[channel].last_S1 = 0;
60  data->channels[channel].last_S2 = 0;
61  }
62 }
63 
64 static void resample_expand(struct snd_pcm_plugin *plugin,
65  const struct snd_pcm_plugin_channel *src_channels,
66  struct snd_pcm_plugin_channel *dst_channels,
67  int src_frames, int dst_frames)
68 {
69  unsigned int pos = 0;
70  signed int val;
71  signed short S1, S2;
72  signed short *src, *dst;
73  unsigned int channel;
74  int src_step, dst_step;
75  int src_frames1, dst_frames1;
76  struct rate_priv *data = (struct rate_priv *)plugin->extra_data;
77  struct rate_channel *rchannels = data->channels;
78 
79  for (channel = 0; channel < plugin->src_format.channels; channel++) {
80  pos = data->pos;
81  S1 = rchannels->last_S1;
82  S2 = rchannels->last_S2;
83  if (!src_channels[channel].enabled) {
84  if (dst_channels[channel].wanted)
85  snd_pcm_area_silence(&dst_channels[channel].area, 0, dst_frames, plugin->dst_format.format);
86  dst_channels[channel].enabled = 0;
87  continue;
88  }
89  dst_channels[channel].enabled = 1;
90  src = (signed short *)src_channels[channel].area.addr +
91  src_channels[channel].area.first / 8 / 2;
92  dst = (signed short *)dst_channels[channel].area.addr +
93  dst_channels[channel].area.first / 8 / 2;
94  src_step = src_channels[channel].area.step / 8 / 2;
95  dst_step = dst_channels[channel].area.step / 8 / 2;
96  src_frames1 = src_frames;
97  dst_frames1 = dst_frames;
98  while (dst_frames1-- > 0) {
99  if (pos & ~R_MASK) {
100  pos &= R_MASK;
101  S1 = S2;
102  if (src_frames1-- > 0) {
103  S2 = *src;
104  src += src_step;
105  }
106  }
107  val = S1 + ((S2 - S1) * (signed int)pos) / BITS;
108  if (val < -32768)
109  val = -32768;
110  else if (val > 32767)
111  val = 32767;
112  *dst = val;
113  dst += dst_step;
114  pos += data->pitch;
115  }
116  rchannels->last_S1 = S1;
117  rchannels->last_S2 = S2;
118  rchannels++;
119  }
120  data->pos = pos;
121 }
122 
123 static void resample_shrink(struct snd_pcm_plugin *plugin,
124  const struct snd_pcm_plugin_channel *src_channels,
125  struct snd_pcm_plugin_channel *dst_channels,
126  int src_frames, int dst_frames)
127 {
128  unsigned int pos = 0;
129  signed int val;
130  signed short S1, S2;
131  signed short *src, *dst;
132  unsigned int channel;
133  int src_step, dst_step;
134  int src_frames1, dst_frames1;
135  struct rate_priv *data = (struct rate_priv *)plugin->extra_data;
136  struct rate_channel *rchannels = data->channels;
137 
138  for (channel = 0; channel < plugin->src_format.channels; ++channel) {
139  pos = data->pos;
140  S1 = rchannels->last_S1;
141  S2 = rchannels->last_S2;
142  if (!src_channels[channel].enabled) {
143  if (dst_channels[channel].wanted)
144  snd_pcm_area_silence(&dst_channels[channel].area, 0, dst_frames, plugin->dst_format.format);
145  dst_channels[channel].enabled = 0;
146  continue;
147  }
148  dst_channels[channel].enabled = 1;
149  src = (signed short *)src_channels[channel].area.addr +
150  src_channels[channel].area.first / 8 / 2;
151  dst = (signed short *)dst_channels[channel].area.addr +
152  dst_channels[channel].area.first / 8 / 2;
153  src_step = src_channels[channel].area.step / 8 / 2;
154  dst_step = dst_channels[channel].area.step / 8 / 2;
155  src_frames1 = src_frames;
156  dst_frames1 = dst_frames;
157  while (dst_frames1 > 0) {
158  S1 = S2;
159  if (src_frames1-- > 0) {
160  S2 = *src;
161  src += src_step;
162  }
163  if (pos & ~R_MASK) {
164  pos &= R_MASK;
165  val = S1 + ((S2 - S1) * (signed int)pos) / BITS;
166  if (val < -32768)
167  val = -32768;
168  else if (val > 32767)
169  val = 32767;
170  *dst = val;
171  dst += dst_step;
172  dst_frames1--;
173  }
174  pos += data->pitch;
175  }
176  rchannels->last_S1 = S1;
177  rchannels->last_S2 = S2;
178  rchannels++;
179  }
180  data->pos = pos;
181 }
182 
183 static snd_pcm_sframes_t rate_src_frames(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t frames)
184 {
185  struct rate_priv *data;
186  snd_pcm_sframes_t res;
187 
188  if (snd_BUG_ON(!plugin))
189  return -ENXIO;
190  if (frames == 0)
191  return 0;
192  data = (struct rate_priv *)plugin->extra_data;
193  if (plugin->src_format.rate < plugin->dst_format.rate) {
194  res = (((frames * data->pitch) + (BITS/2)) >> SHIFT);
195  } else {
196  res = (((frames << SHIFT) + (data->pitch / 2)) / data->pitch);
197  }
198  if (data->old_src_frames > 0) {
199  snd_pcm_sframes_t frames1 = frames, res1 = data->old_dst_frames;
200  while (data->old_src_frames < frames1) {
201  frames1 >>= 1;
202  res1 <<= 1;
203  }
204  while (data->old_src_frames > frames1) {
205  frames1 <<= 1;
206  res1 >>= 1;
207  }
208  if (data->old_src_frames == frames1)
209  return res1;
210  }
211  data->old_src_frames = frames;
212  data->old_dst_frames = res;
213  return res;
214 }
215 
216 static snd_pcm_sframes_t rate_dst_frames(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t frames)
217 {
218  struct rate_priv *data;
219  snd_pcm_sframes_t res;
220 
221  if (snd_BUG_ON(!plugin))
222  return -ENXIO;
223  if (frames == 0)
224  return 0;
225  data = (struct rate_priv *)plugin->extra_data;
226  if (plugin->src_format.rate < plugin->dst_format.rate) {
227  res = (((frames << SHIFT) + (data->pitch / 2)) / data->pitch);
228  } else {
229  res = (((frames * data->pitch) + (BITS/2)) >> SHIFT);
230  }
231  if (data->old_dst_frames > 0) {
232  snd_pcm_sframes_t frames1 = frames, res1 = data->old_src_frames;
233  while (data->old_dst_frames < frames1) {
234  frames1 >>= 1;
235  res1 <<= 1;
236  }
237  while (data->old_dst_frames > frames1) {
238  frames1 <<= 1;
239  res1 >>= 1;
240  }
241  if (data->old_dst_frames == frames1)
242  return res1;
243  }
244  data->old_dst_frames = frames;
245  data->old_src_frames = res;
246  return res;
247 }
248 
249 static snd_pcm_sframes_t rate_transfer(struct snd_pcm_plugin *plugin,
250  const struct snd_pcm_plugin_channel *src_channels,
251  struct snd_pcm_plugin_channel *dst_channels,
252  snd_pcm_uframes_t frames)
253 {
254  snd_pcm_uframes_t dst_frames;
255  struct rate_priv *data;
256 
257  if (snd_BUG_ON(!plugin || !src_channels || !dst_channels))
258  return -ENXIO;
259  if (frames == 0)
260  return 0;
261 #ifdef CONFIG_SND_DEBUG
262  {
263  unsigned int channel;
264  for (channel = 0; channel < plugin->src_format.channels; channel++) {
265  if (snd_BUG_ON(src_channels[channel].area.first % 8 ||
266  src_channels[channel].area.step % 8))
267  return -ENXIO;
268  if (snd_BUG_ON(dst_channels[channel].area.first % 8 ||
269  dst_channels[channel].area.step % 8))
270  return -ENXIO;
271  }
272  }
273 #endif
274 
275  dst_frames = rate_dst_frames(plugin, frames);
276  if (dst_frames > dst_channels[0].frames)
277  dst_frames = dst_channels[0].frames;
278  data = (struct rate_priv *)plugin->extra_data;
279  data->func(plugin, src_channels, dst_channels, frames, dst_frames);
280  return dst_frames;
281 }
282 
283 static int rate_action(struct snd_pcm_plugin *plugin,
284  enum snd_pcm_plugin_action action,
285  unsigned long udata)
286 {
287  if (snd_BUG_ON(!plugin))
288  return -ENXIO;
289  switch (action) {
290  case INIT:
291  case PREPARE:
292  rate_init(plugin);
293  break;
294  default:
295  break;
296  }
297  return 0; /* silenty ignore other actions */
298 }
299 
300 int snd_pcm_plugin_build_rate(struct snd_pcm_substream *plug,
301  struct snd_pcm_plugin_format *src_format,
302  struct snd_pcm_plugin_format *dst_format,
303  struct snd_pcm_plugin **r_plugin)
304 {
305  int err;
306  struct rate_priv *data;
307  struct snd_pcm_plugin *plugin;
308 
309  if (snd_BUG_ON(!r_plugin))
310  return -ENXIO;
311  *r_plugin = NULL;
312 
313  if (snd_BUG_ON(src_format->channels != dst_format->channels))
314  return -ENXIO;
315  if (snd_BUG_ON(src_format->channels <= 0))
316  return -ENXIO;
317  if (snd_BUG_ON(src_format->format != SNDRV_PCM_FORMAT_S16))
318  return -ENXIO;
319  if (snd_BUG_ON(dst_format->format != SNDRV_PCM_FORMAT_S16))
320  return -ENXIO;
321  if (snd_BUG_ON(src_format->rate == dst_format->rate))
322  return -ENXIO;
323 
324  err = snd_pcm_plugin_build(plug, "rate conversion",
325  src_format, dst_format,
326  sizeof(struct rate_priv) +
327  src_format->channels * sizeof(struct rate_channel),
328  &plugin);
329  if (err < 0)
330  return err;
331  data = (struct rate_priv *)plugin->extra_data;
332  if (src_format->rate < dst_format->rate) {
333  data->pitch = ((src_format->rate << SHIFT) + (dst_format->rate >> 1)) / dst_format->rate;
334  data->func = resample_expand;
335  } else {
336  data->pitch = ((dst_format->rate << SHIFT) + (src_format->rate >> 1)) / src_format->rate;
337  data->func = resample_shrink;
338  }
339  data->pos = 0;
340  rate_init(plugin);
341  data->old_src_frames = data->old_dst_frames = 0;
342  plugin->transfer = rate_transfer;
343  plugin->src_frames = rate_src_frames;
344  plugin->dst_frames = rate_dst_frames;
345  plugin->action = rate_action;
346  *r_plugin = plugin;
347  return 0;
348 }
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