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-rw-r--r--sound/core/oss/mulaw.c308
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diff --git a/sound/core/oss/mulaw.c b/sound/core/oss/mulaw.c
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+/*
+ * Mu-Law conversion Plug-In Interface
+ * Copyright (c) 1999 by Jaroslav Kysela <perex@suse.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 <sound/driver.h>
+#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)(snd_pcm_plugin_t *plugin,
+ const snd_pcm_plugin_channel_t *src_channels,
+ snd_pcm_plugin_channel_t *dst_channels,
+ snd_pcm_uframes_t frames);
+
+typedef struct mulaw_private_data {
+ mulaw_f func;
+ int conv;
+} mulaw_t;
+
+static void mulaw_decode(snd_pcm_plugin_t *plugin,
+ const snd_pcm_plugin_channel_t *src_channels,
+ snd_pcm_plugin_channel_t *dst_channels,
+ snd_pcm_uframes_t frames)
+{
+#define PUT_S16_LABELS
+#include "plugin_ops.h"
+#undef PUT_S16_LABELS
+ mulaw_t *data = (mulaw_t *)plugin->extra_data;
+ void *put = put_s16_labels[data->conv];
+ 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);
+ goto *put;
+#define PUT_S16_END after
+#include "plugin_ops.h"
+#undef PUT_S16_END
+ after:
+ src += src_step;
+ dst += dst_step;
+ }
+ }
+}
+
+static void mulaw_encode(snd_pcm_plugin_t *plugin,
+ const snd_pcm_plugin_channel_t *src_channels,
+ snd_pcm_plugin_channel_t *dst_channels,
+ snd_pcm_uframes_t frames)
+{
+#define GET_S16_LABELS
+#include "plugin_ops.h"
+#undef GET_S16_LABELS
+ mulaw_t *data = (mulaw_t *)plugin->extra_data;
+ void *get = get_s16_labels[data->conv];
+ int channel;
+ int nchannels = plugin->src_format.channels;
+ signed short sample = 0;
+ 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) {
+ goto *get;
+#define GET_S16_END after
+#include "plugin_ops.h"
+#undef GET_S16_END
+ after:
+ *dst = linear2ulaw(sample);
+ src += src_step;
+ dst += dst_step;
+ }
+ }
+}
+
+static snd_pcm_sframes_t mulaw_transfer(snd_pcm_plugin_t *plugin,
+ const snd_pcm_plugin_channel_t *src_channels,
+ snd_pcm_plugin_channel_t *dst_channels,
+ snd_pcm_uframes_t frames)
+{
+ mulaw_t *data;
+
+ snd_assert(plugin != NULL && src_channels != NULL && dst_channels != NULL, return -ENXIO);
+ if (frames == 0)
+ return 0;
+#ifdef CONFIG_SND_DEBUG
+ {
+ unsigned int channel;
+ for (channel = 0; channel < plugin->src_format.channels; channel++) {
+ snd_assert(src_channels[channel].area.first % 8 == 0 &&
+ src_channels[channel].area.step % 8 == 0,
+ return -ENXIO);
+ snd_assert(dst_channels[channel].area.first % 8 == 0 &&
+ dst_channels[channel].area.step % 8 == 0,
+ return -ENXIO);
+ }
+ }
+#endif
+ data = (mulaw_t *)plugin->extra_data;
+ data->func(plugin, src_channels, dst_channels, frames);
+ return frames;
+}
+
+int snd_pcm_plugin_build_mulaw(snd_pcm_plug_t *plug,
+ snd_pcm_plugin_format_t *src_format,
+ snd_pcm_plugin_format_t *dst_format,
+ snd_pcm_plugin_t **r_plugin)
+{
+ int err;
+ mulaw_t *data;
+ snd_pcm_plugin_t *plugin;
+ snd_pcm_plugin_format_t *format;
+ mulaw_f func;
+
+ snd_assert(r_plugin != NULL, return -ENXIO);
+ *r_plugin = NULL;
+
+ snd_assert(src_format->rate == dst_format->rate, return -ENXIO);
+ snd_assert(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;
+ }
+ snd_assert(snd_pcm_format_linear(format->format) != 0, return -ENXIO);
+
+ err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion",
+ src_format, dst_format,
+ sizeof(mulaw_t), &plugin);
+ if (err < 0)
+ return err;
+ data = (mulaw_t*)plugin->extra_data;
+ data->func = func;
+ data->conv = getput_index(format->format);
+ snd_assert(data->conv >= 0 && data->conv < 4*2*2, return -EINVAL);
+ plugin->transfer = mulaw_transfer;
+ *r_plugin = plugin;
+ return 0;
+}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.