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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;
}

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