linux/sound/core/oss/linear.c
<<
>>
Prefs
   1/*
   2 *  Linear conversion Plug-In
   3 *  Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz>,
   4 *                        Abramo Bagnara <abramo@alsa-project.org>
   5 *
   6 *
   7 *   This library is free software; you can redistribute it and/or modify
   8 *   it under the terms of the GNU Library General Public License as
   9 *   published by the Free Software Foundation; either version 2 of
  10 *   the License, or (at your option) any later version.
  11 *
  12 *   This program is distributed in the hope that it will be useful,
  13 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 *   GNU Library General Public License for more details.
  16 *
  17 *   You should have received a copy of the GNU Library General Public
  18 *   License along with this library; if not, write to the Free Software
  19 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  20 *
  21 */
  22
  23#include <linux/time.h>
  24#include <sound/core.h>
  25#include <sound/pcm.h>
  26#include "pcm_plugin.h"
  27
  28/*
  29 *  Basic linear conversion plugin
  30 */
  31 
  32struct linear_priv {
  33        int cvt_endian;         /* need endian conversion? */
  34        unsigned int src_ofs;   /* byte offset in source format */
  35        unsigned int dst_ofs;   /* byte soffset in destination format */
  36        unsigned int copy_ofs;  /* byte offset in temporary u32 data */
  37        unsigned int dst_bytes;         /* byte size of destination format */
  38        unsigned int copy_bytes;        /* bytes to copy per conversion */
  39        unsigned int flip; /* MSB flip for signeness, done after endian conv */
  40};
  41
  42static inline void do_convert(struct linear_priv *data,
  43                              unsigned char *dst, unsigned char *src)
  44{
  45        unsigned int tmp = 0;
  46        unsigned char *p = (unsigned char *)&tmp;
  47
  48        memcpy(p + data->copy_ofs, src + data->src_ofs, data->copy_bytes);
  49        if (data->cvt_endian)
  50                tmp = swab32(tmp);
  51        tmp ^= data->flip;
  52        memcpy(dst, p + data->dst_ofs, data->dst_bytes);
  53}
  54
  55static void convert(struct snd_pcm_plugin *plugin,
  56                    const struct snd_pcm_plugin_channel *src_channels,
  57                    struct snd_pcm_plugin_channel *dst_channels,
  58                    snd_pcm_uframes_t frames)
  59{
  60        struct linear_priv *data = (struct linear_priv *)plugin->extra_data;
  61        int channel;
  62        int nchannels = plugin->src_format.channels;
  63        for (channel = 0; channel < nchannels; ++channel) {
  64                char *src;
  65                char *dst;
  66                int src_step, dst_step;
  67                snd_pcm_uframes_t frames1;
  68                if (!src_channels[channel].enabled) {
  69                        if (dst_channels[channel].wanted)
  70                                snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
  71                        dst_channels[channel].enabled = 0;
  72                        continue;
  73                }
  74                dst_channels[channel].enabled = 1;
  75                src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
  76                dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
  77                src_step = src_channels[channel].area.step / 8;
  78                dst_step = dst_channels[channel].area.step / 8;
  79                frames1 = frames;
  80                while (frames1-- > 0) {
  81                        do_convert(data, dst, src);
  82                        src += src_step;
  83                        dst += dst_step;
  84                }
  85        }
  86}
  87
  88static snd_pcm_sframes_t linear_transfer(struct snd_pcm_plugin *plugin,
  89                               const struct snd_pcm_plugin_channel *src_channels,
  90                               struct snd_pcm_plugin_channel *dst_channels,
  91                               snd_pcm_uframes_t frames)
  92{
  93        if (snd_BUG_ON(!plugin || !src_channels || !dst_channels))
  94                return -ENXIO;
  95        if (frames == 0)
  96                return 0;
  97#ifdef CONFIG_SND_DEBUG
  98        {
  99                unsigned int channel;
 100                for (channel = 0; channel < plugin->src_format.channels; channel++) {
 101                        if (snd_BUG_ON(src_channels[channel].area.first % 8 ||
 102                                       src_channels[channel].area.step % 8))
 103                                return -ENXIO;
 104                        if (snd_BUG_ON(dst_channels[channel].area.first % 8 ||
 105                                       dst_channels[channel].area.step % 8))
 106                                return -ENXIO;
 107                }
 108        }
 109#endif
 110        if (frames > dst_channels[0].frames)
 111                frames = dst_channels[0].frames;
 112        convert(plugin, src_channels, dst_channels, frames);
 113        return frames;
 114}
 115
 116static void init_data(struct linear_priv *data,
 117                      snd_pcm_format_t src_format, snd_pcm_format_t dst_format)
 118{
 119        int src_le, dst_le, src_bytes, dst_bytes;
 120
 121        src_bytes = snd_pcm_format_width(src_format) / 8;
 122        dst_bytes = snd_pcm_format_width(dst_format) / 8;
 123        src_le = snd_pcm_format_little_endian(src_format) > 0;
 124        dst_le = snd_pcm_format_little_endian(dst_format) > 0;
 125
 126        data->dst_bytes = dst_bytes;
 127        data->cvt_endian = src_le != dst_le;
 128        data->copy_bytes = src_bytes < dst_bytes ? src_bytes : dst_bytes;
 129        if (src_le) {
 130                data->copy_ofs = 4 - data->copy_bytes;
 131                data->src_ofs = src_bytes - data->copy_bytes;
 132        } else
 133                data->src_ofs = snd_pcm_format_physical_width(src_format) / 8 -
 134                        src_bytes;
 135        if (dst_le)
 136                data->dst_ofs = 4 - data->dst_bytes;
 137        else
 138                data->dst_ofs = snd_pcm_format_physical_width(dst_format) / 8 -
 139                        dst_bytes;
 140        if (snd_pcm_format_signed(src_format) !=
 141            snd_pcm_format_signed(dst_format)) {
 142                if (dst_le)
 143                        data->flip = (__force u32)cpu_to_le32(0x80000000);
 144                else
 145                        data->flip = (__force u32)cpu_to_be32(0x80000000);
 146        }
 147}
 148
 149int snd_pcm_plugin_build_linear(struct snd_pcm_substream *plug,
 150                                struct snd_pcm_plugin_format *src_format,
 151                                struct snd_pcm_plugin_format *dst_format,
 152                                struct snd_pcm_plugin **r_plugin)
 153{
 154        int err;
 155        struct linear_priv *data;
 156        struct snd_pcm_plugin *plugin;
 157
 158        if (snd_BUG_ON(!r_plugin))
 159                return -ENXIO;
 160        *r_plugin = NULL;
 161
 162        if (snd_BUG_ON(src_format->rate != dst_format->rate))
 163                return -ENXIO;
 164        if (snd_BUG_ON(src_format->channels != dst_format->channels))
 165                return -ENXIO;
 166        if (snd_BUG_ON(!snd_pcm_format_linear(src_format->format) ||
 167                       !snd_pcm_format_linear(dst_format->format)))
 168                return -ENXIO;
 169
 170        err = snd_pcm_plugin_build(plug, "linear format conversion",
 171                                   src_format, dst_format,
 172                                   sizeof(struct linear_priv), &plugin);
 173        if (err < 0)
 174                return err;
 175        data = (struct linear_priv *)plugin->extra_data;
 176        init_data(data, src_format->format, dst_format->format);
 177        plugin->transfer = linear_transfer;
 178        *r_plugin = plugin;
 179        return 0;
 180}
 181
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.