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Diffstat (limited to 'sound/core/oss/mulaw.c')
| -rw-r--r-- | sound/core/oss/mulaw.c | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/sound/core/oss/mulaw.c b/sound/core/oss/mulaw.c new file mode 100644 index 0000000..f7649d4 --- /dev/null +++ b/sound/core/oss/mulaw.c @@ -0,0 +1,344 @@ +/* + * Mu-Law conversion Plug-In Interface + * Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz> + * Uros Bizjak <uros@kss-loka.si> + * + * Based on reference implementation by Sun Microsystems, Inc. + * + * 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 SIGN_BIT (0x80) /* Sign bit for a u-law byte. */ +#define QUANT_MASK (0xf) /* Quantization field mask. */ +#define NSEGS (8) /* Number of u-law segments. */ +#define SEG_SHIFT (4) /* Left shift for segment number. */ +#define SEG_MASK (0x70) /* Segment field mask. */ + +static inline int val_seg(int val) +{ + int r = 0; + val >>= 7; + if (val & 0xf0) { + val >>= 4; + r += 4; + } + if (val & 0x0c) { + val >>= 2; + r += 2; + } + if (val & 0x02) + r += 1; + return r; +} + +#define BIAS (0x84) /* Bias for linear code. */ + +/* + * linear2ulaw() - Convert a linear PCM value to u-law + * + * In order to simplify the encoding process, the original linear magnitude + * is biased by adding 33 which shifts the encoding range from (0 - 8158) to + * (33 - 8191). The result can be seen in the following encoding table: + * + * Biased Linear Input Code Compressed Code + * ------------------------ --------------- + * 00000001wxyza 000wxyz + * 0000001wxyzab 001wxyz + * 000001wxyzabc 010wxyz + * 00001wxyzabcd 011wxyz + * 0001wxyzabcde 100wxyz + * 001wxyzabcdef 101wxyz + * 01wxyzabcdefg 110wxyz + * 1wxyzabcdefgh 111wxyz + * + * Each biased linear code has a leading 1 which identifies the segment + * number. The value of the segment number is equal to 7 minus the number + * of leading 0's. The quantization interval is directly available as the + * four bits wxyz. * The trailing bits (a - h) are ignored. + * + * Ordinarily the complement of the resulting code word is used for + * transmission, and so the code word is complemented before it is returned. + * + * For further information see John C. Bellamy's Digital Telephony, 1982, + * John Wiley & Sons, pps 98-111 and 472-476. + */ +static unsigned char linear2ulaw(int pcm_val) /* 2's complement (16-bit range) */ +{ + int mask; + int seg; + unsigned char uval; + + /* Get the sign and the magnitude of the value. */ + if (pcm_val < 0) { + pcm_val = BIAS - pcm_val; + mask = 0x7F; + } else { + pcm_val += BIAS; + mask = 0xFF; + } + if (pcm_val > 0x7FFF) + pcm_val = 0x7FFF; + + /* Convert the scaled magnitude to segment number. */ + seg = val_seg(pcm_val); + + /* + * Combine the sign, segment, quantization bits; + * and complement the code word. + */ + uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF); + return uval ^ mask; +} + +/* + * ulaw2linear() - Convert a u-law value to 16-bit linear PCM + * + * First, a biased linear code is derived from the code word. An unbiased + * output can then be obtained by subtracting 33 from the biased code. + * + * Note that this function expects to be passed the complement of the + * original code word. This is in keeping with ISDN conventions. + */ +static int ulaw2linear(unsigned char u_val) +{ + int t; + + /* Complement to obtain normal u-law value. */ + u_val = ~u_val; + + /* + * Extract and bias the quantization bits. Then + * shift up by the segment number and subtract out the bias. + */ + t = ((u_val & QUANT_MASK) << 3) + BIAS; + t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT; + + return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS)); +} + +/* + * Basic Mu-Law plugin + */ + +typedef void (*mulaw_f)(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); + +struct mulaw_priv { + mulaw_f func; + int cvt_endian; /* need endian conversion? */ + unsigned int native_ofs; /* byte offset in native format */ + unsigned int copy_ofs; /* byte offset in s16 format */ + unsigned int native_bytes; /* byte size of the native format */ + unsigned int copy_bytes; /* bytes to copy per conversion */ + u16 flip; /* MSB flip for signedness, done after endian conversion */ +}; + +static inline void cvt_s16_to_native(struct mulaw_priv *data, + unsigned char *dst, u16 sample) +{ + sample ^= data->flip; + if (data->cvt_endian) + sample = swab16(sample); + if (data->native_bytes > data->copy_bytes) + memset(dst, 0, data->native_bytes); + memcpy(dst + data->native_ofs, (char *)&sample + data->copy_ofs, + data->copy_bytes); +} + +static void mulaw_decode(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) +{ + struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; + int channel; + int nchannels = plugin->src_format.channels; + for (channel = 0; channel < nchannels; ++channel) { + char *src; + char *dst; + int src_step, dst_step; + snd_pcm_uframes_t frames1; + if (!src_channels[channel].enabled) { + if (dst_channels[channel].wanted) + snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format); + dst_channels[channel].enabled = 0; + continue; + } + dst_channels[channel].enabled = 1; + src = src_channels[channel].area.addr + src_channels[channel].area.first / 8; + dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8; + src_step = src_channels[channel].area.step / 8; + dst_step = dst_channels[channel].area.step / 8; + frames1 = frames; + while (frames1-- > 0) { + signed short sample = ulaw2linear(*src); + cvt_s16_to_native(data, dst, sample); + src += src_step; + dst += dst_step; + } + } +} + +static inline signed short cvt_native_to_s16(struct mulaw_priv *data, + unsigned char *src) +{ + u16 sample = 0; + memcpy((char *)&sample + data->copy_ofs, src + data->native_ofs, + data->copy_bytes); + if (data->cvt_endian) + sample = swab16(sample); + sample ^= data->flip; + return (signed short)sample; +} + +static void mulaw_encode(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) +{ + struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data; + int channel; + int nchannels = plugin->src_format.channels; + for (channel = 0; channel < nchannels; ++channel) { + char *src; + char *dst; + int src_step, dst_step; + snd_pcm_uframes_t frames1; + if (!src_channels[channel].enabled) { + if (dst_channels[channel].wanted) + snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format); + dst_channels[channel].enabled = 0; + continue; + } + dst_channels[channel].enabled = 1; + src = src_channels[channel].area.addr + src_channels[channel].area.first / 8; + dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8; + src_step = src_channels[channel].area.step / 8; + dst_step = dst_channels[channel].area.step / 8; + frames1 = frames; + while (frames1-- > 0) { + signed short sample = cvt_native_to_s16(data, src); + *dst = linear2ulaw(sample); + src += src_step; + dst += dst_step; + } + } +} + +static snd_pcm_sframes_t mulaw_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) +{ + struct mulaw_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 + data = (struct mulaw_priv *)plugin->extra_data; + data->func(plugin, src_channels, dst_channels, frames); + return frames; +} + +static void init_data(struct mulaw_priv *data, int format) +{ +#ifdef SNDRV_LITTLE_ENDIAN + data->cvt_endian = snd_pcm_format_big_endian(format) > 0; +#else + data->cvt_endian = snd_pcm_format_little_endian(format) > 0; +#endif + if (!snd_pcm_format_signed(format)) + data->flip = 0x8000; + data->native_bytes = snd_pcm_format_physical_width(format) / 8; + data->copy_bytes = data->native_bytes < 2 ? 1 : 2; + if (snd_pcm_format_little_endian(format)) { + data->native_ofs = data->native_bytes - data->copy_bytes; + data->copy_ofs = 2 - data->copy_bytes; + } else { + /* S24 in 4bytes need an 1 byte offset */ + data->native_ofs = data->native_bytes - + snd_pcm_format_width(format) / 8; + } +} + +int snd_pcm_plugin_build_mulaw(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 mulaw_priv *data; + struct snd_pcm_plugin *plugin; + struct snd_pcm_plugin_format *format; + mulaw_f func; + + if (snd_BUG_ON(!r_plugin)) + return -ENXIO; + *r_plugin = NULL; + + if (snd_BUG_ON(src_format->rate != dst_format->rate)) + return -ENXIO; + if (snd_BUG_ON(src_format->channels != dst_format->channels)) + return -ENXIO; + + if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) { + format = src_format; + func = mulaw_encode; + } + else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) { + format = dst_format; + func = mulaw_decode; + } + else { + snd_BUG(); + return -EINVAL; + } + if (snd_BUG_ON(!snd_pcm_format_linear(format->format))) + return -ENXIO; + + err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion", + src_format, dst_format, + sizeof(struct mulaw_priv), &plugin); + if (err < 0) + return err; + data = (struct mulaw_priv *)plugin->extra_data; + data->func = func; + init_data(data, format->format); + plugin->transfer = mulaw_transfer; + *r_plugin = plugin; + return 0; +} |
