1/*
2 *  Mu-Law conversion Plug-In Interface
3 *  Copyright (c) 1999 by Jaroslav Kysela <perex@suse.cz>
4 *                        Uros Bizjak <uros@kss-loka.si>
5 *
6 *  Based on reference implementation by Sun Microsystems, Inc.
7 *
8 *   This library is free software; you can redistribute it and/or modify
9 *   it under the terms of the GNU Library General Public License as
10 *   published by the Free Software Foundation; either version 2 of
11 *   the License, or (at your option) any later version.
12 *
13 *   This program is distributed in the hope that it will be useful,
14 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
15 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16 *   GNU Library General Public License for more details.
17 *
18 *   You should have received a copy of the GNU Library General Public
19 *   License along with this library; if not, write to the Free Software
20 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
21 *
22 */
23
24#include <sound/driver.h>
25
26#ifdef CONFIG_SND_PCM_OSS_PLUGINS
27
28#include <linux/time.h>
29#include <sound/core.h>
30#include <sound/pcm.h>
31#include "pcm_plugin.h"
32
33#define	SIGN_BIT	(0x80)		/* Sign bit for a u-law byte. */
34#define	QUANT_MASK	(0xf)		/* Quantization field mask. */
35#define	NSEGS		(8)		/* Number of u-law segments. */
36#define	SEG_SHIFT	(4)		/* Left shift for segment number. */
37#define	SEG_MASK	(0x70)		/* Segment field mask. */
38
39static inline int val_seg(int val)
40{
41	int r = 0;
42	val >>= 7;
43	if (val & 0xf0) {
44		val >>= 4;
45		r += 4;
46	}
47	if (val & 0x0c) {
48		val >>= 2;
49		r += 2;
50	}
51	if (val & 0x02)
52		r += 1;
53	return r;
54}
55
56#define	BIAS		(0x84)		/* Bias for linear code. */
57
58/*
59 * linear2ulaw() - Convert a linear PCM value to u-law
60 *
61 * In order to simplify the encoding process, the original linear magnitude
62 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
63 * (33 - 8191). The result can be seen in the following encoding table:
64 *
65 *	Biased Linear Input Code	Compressed Code
66 *	------------------------	---------------
67 *	00000001wxyza			000wxyz
68 *	0000001wxyzab			001wxyz
69 *	000001wxyzabc			010wxyz
70 *	00001wxyzabcd			011wxyz
71 *	0001wxyzabcde			100wxyz
72 *	001wxyzabcdef			101wxyz
73 *	01wxyzabcdefg			110wxyz
74 *	1wxyzabcdefgh			111wxyz
75 *
76 * Each biased linear code has a leading 1 which identifies the segment
77 * number. The value of the segment number is equal to 7 minus the number
78 * of leading 0's. The quantization interval is directly available as the
79 * four bits wxyz.  * The trailing bits (a - h) are ignored.
80 *
81 * Ordinarily the complement of the resulting code word is used for
82 * transmission, and so the code word is complemented before it is returned.
83 *
84 * For further information see John C. Bellamy's Digital Telephony, 1982,
85 * John Wiley & Sons, pps 98-111 and 472-476.
86 */
87static unsigned char linear2ulaw(int pcm_val)	/* 2's complement (16-bit range) */
88{
89	int mask;
90	int seg;
91	unsigned char uval;
92
93	/* Get the sign and the magnitude of the value. */
94	if (pcm_val < 0) {
95		pcm_val = BIAS - pcm_val;
96		mask = 0x7F;
97	} else {
98		pcm_val += BIAS;
99		mask = 0xFF;
100	}
101	if (pcm_val > 0x7FFF)
102		pcm_val = 0x7FFF;
103
104	/* Convert the scaled magnitude to segment number. */
105	seg = val_seg(pcm_val);
106
107	/*
108	 * Combine the sign, segment, quantization bits;
109	 * and complement the code word.
110	 */
111	uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
112	return uval ^ mask;
113}
114
115/*
116 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
117 *
118 * First, a biased linear code is derived from the code word. An unbiased
119 * output can then be obtained by subtracting 33 from the biased code.
120 *
121 * Note that this function expects to be passed the complement of the
122 * original code word. This is in keeping with ISDN conventions.
123 */
124static int ulaw2linear(unsigned char u_val)
125{
126	int t;
127
128	/* Complement to obtain normal u-law value. */
129	u_val = ~u_val;
130
131	/*
132	 * Extract and bias the quantization bits. Then
133	 * shift up by the segment number and subtract out the bias.
134	 */
135	t = ((u_val & QUANT_MASK) << 3) + BIAS;
136	t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
137
138	return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
139}
140
141/*
142 *  Basic Mu-Law plugin
143 */
144
145typedef void (*mulaw_f)(struct snd_pcm_plugin *plugin,
146			const struct snd_pcm_plugin_channel *src_channels,
147			struct snd_pcm_plugin_channel *dst_channels,
148			snd_pcm_uframes_t frames);
149
150struct mulaw_priv {
151	mulaw_f func;
152	int conv;
153};
154
155static void mulaw_decode(struct snd_pcm_plugin *plugin,
156			const struct snd_pcm_plugin_channel *src_channels,
157			struct snd_pcm_plugin_channel *dst_channels,
158			snd_pcm_uframes_t frames)
159{
160#define PUT_S16_LABELS
161#include "plugin_ops.h"
162#undef PUT_S16_LABELS
163	struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;
164	void *put = put_s16_labels[data->conv];
165	int channel;
166	int nchannels = plugin->src_format.channels;
167	for (channel = 0; channel < nchannels; ++channel) {
168		char *src;
169		char *dst;
170		int src_step, dst_step;
171		snd_pcm_uframes_t frames1;
172		if (!src_channels[channel].enabled) {
173			if (dst_channels[channel].wanted)
174				snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
175			dst_channels[channel].enabled = 0;
176			continue;
177		}
178		dst_channels[channel].enabled = 1;
179		src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
180		dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
181		src_step = src_channels[channel].area.step / 8;
182		dst_step = dst_channels[channel].area.step / 8;
183		frames1 = frames;
184		while (frames1-- > 0) {
185			signed short sample = ulaw2linear(*src);
186			goto *put;
187#define PUT_S16_END after
188#include "plugin_ops.h"
189#undef PUT_S16_END
190		after:
191			src += src_step;
192			dst += dst_step;
193		}
194	}
195}
196
197static void mulaw_encode(struct snd_pcm_plugin *plugin,
198			const struct snd_pcm_plugin_channel *src_channels,
199			struct snd_pcm_plugin_channel *dst_channels,
200			snd_pcm_uframes_t frames)
201{
202#define GET_S16_LABELS
203#include "plugin_ops.h"
204#undef GET_S16_LABELS
205	struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;
206	void *get = get_s16_labels[data->conv];
207	int channel;
208	int nchannels = plugin->src_format.channels;
209	signed short sample = 0;
210	for (channel = 0; channel < nchannels; ++channel) {
211		char *src;
212		char *dst;
213		int src_step, dst_step;
214		snd_pcm_uframes_t frames1;
215		if (!src_channels[channel].enabled) {
216			if (dst_channels[channel].wanted)
217				snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
218			dst_channels[channel].enabled = 0;
219			continue;
220		}
221		dst_channels[channel].enabled = 1;
222		src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
223		dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
224		src_step = src_channels[channel].area.step / 8;
225		dst_step = dst_channels[channel].area.step / 8;
226		frames1 = frames;
227		while (frames1-- > 0) {
228			goto *get;
229#define GET_S16_END after
230#include "plugin_ops.h"
231#undef GET_S16_END
232		after:
233			*dst = linear2ulaw(sample);
234			src += src_step;
235			dst += dst_step;
236		}
237	}
238}
239
240static snd_pcm_sframes_t mulaw_transfer(struct snd_pcm_plugin *plugin,
241			      const struct snd_pcm_plugin_channel *src_channels,
242			      struct snd_pcm_plugin_channel *dst_channels,
243			      snd_pcm_uframes_t frames)
244{
245	struct mulaw_priv *data;
246
247	snd_assert(plugin != NULL && src_channels != NULL && dst_channels != NULL, return -ENXIO);
248	if (frames == 0)
249		return 0;
250#ifdef CONFIG_SND_DEBUG
251	{
252		unsigned int channel;
253		for (channel = 0; channel < plugin->src_format.channels; channel++) {
254			snd_assert(src_channels[channel].area.first % 8 == 0 &&
255				   src_channels[channel].area.step % 8 == 0,
256				   return -ENXIO);
257			snd_assert(dst_channels[channel].area.first % 8 == 0 &&
258				   dst_channels[channel].area.step % 8 == 0,
259				   return -ENXIO);
260		}
261	}
262#endif
263	data = (struct mulaw_priv *)plugin->extra_data;
264	data->func(plugin, src_channels, dst_channels, frames);
265	return frames;
266}
267
268static int getput_index(int format)
269{
270	int sign, width, endian;
271	sign = !snd_pcm_format_signed(format);
272	width = snd_pcm_format_width(format) / 8 - 1;
273	if (width < 0 || width > 3) {
274		snd_printk(KERN_ERR "snd-pcm-oss: invalid format %d\n", format);
275		width = 0;
276	}
277#ifdef SNDRV_LITTLE_ENDIAN
278	endian = snd_pcm_format_big_endian(format);
279#else
280	endian = snd_pcm_format_little_endian(format);
281#endif
282	if (endian < 0)
283		endian = 0;
284	return width * 4 + endian * 2 + sign;
285}
286
287int snd_pcm_plugin_build_mulaw(struct snd_pcm_substream *plug,
288			       struct snd_pcm_plugin_format *src_format,
289			       struct snd_pcm_plugin_format *dst_format,
290			       struct snd_pcm_plugin **r_plugin)
291{
292	int err;
293	struct mulaw_priv *data;
294	struct snd_pcm_plugin *plugin;
295	struct snd_pcm_plugin_format *format;
296	mulaw_f func;
297
298	snd_assert(r_plugin != NULL, return -ENXIO);
299	*r_plugin = NULL;
300
301	snd_assert(src_format->rate == dst_format->rate, return -ENXIO);
302	snd_assert(src_format->channels == dst_format->channels, return -ENXIO);
303
304	if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) {
305		format = src_format;
306		func = mulaw_encode;
307	}
308	else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) {
309		format = dst_format;
310		func = mulaw_decode;
311	}
312	else {
313		snd_BUG();
314		return -EINVAL;
315	}
316	snd_assert(snd_pcm_format_linear(format->format) != 0, return -ENXIO);
317
318	err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion",
319				   src_format, dst_format,
320				   sizeof(struct mulaw_priv), &plugin);
321	if (err < 0)
322		return err;
323	data = (struct mulaw_priv *)plugin->extra_data;
324	data->func = func;
325	data->conv = getput_index(format->format);
326	snd_assert(data->conv >= 0 && data->conv < 4*2*2, return -EINVAL);
327	plugin->transfer = mulaw_transfer;
328	*r_plugin = plugin;
329	return 0;
330}
331
332#endif
333