2  *  Mu-Law conversion Plug-In Interface
4  *                        Uros Bizjak <uros@kss-loka.si>
20  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
29 #define	SIGN_BIT	(0x80)		/* Sign bit for a u-law byte. */
31 #define	NSEGS		(8)		/* Number of u-law segments. */
55  * linear2ulaw() - Convert a linear PCM value to u-law
58  * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
59  * (33 - 8191). The result can be seen in the following encoding table:
62  *	------------------------	---------------
75  * four bits wxyz.  * The trailing bits (a - h) are ignored.
81  * John Wiley & Sons, pps 98-111 and 472-476.
83 static unsigned char linear2ulaw(int pcm_val)	/* 2's complement (16-bit range) */  in linear2ulaw()
91 		pcm_val = BIAS - pcm_val;  in linear2ulaw()
100 	/* Convert the scaled magnitude to segment number. */  in linear2ulaw()
112  * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
124 	/* Complement to obtain normal u-law value. */  in ulaw2linear()
134 	return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));  in ulaw2linear()
138  *  Basic Mu-Law plugin
159 	sample ^= data->flip;  in cvt_s16_to_native()
160 	if (data->cvt_endian)  in cvt_s16_to_native()
162 	if (data->native_bytes > data->copy_bytes)  in cvt_s16_to_native()
163 		memset(dst, 0, data->native_bytes);  in cvt_s16_to_native()
164 	memcpy(dst + data->native_ofs, (char *)&sample + data->copy_ofs,  in cvt_s16_to_native()
165 	       data->copy_bytes);  in cvt_s16_to_native()
173 	struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;  in mulaw_decode()
175 	int nchannels = plugin->src_format.channels;  in mulaw_decode()
183 				snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);  in mulaw_decode()
193 		while (frames1-- > 0) {  in mulaw_decode()
206 	memcpy((char *)&sample + data->copy_ofs, src + data->native_ofs,  in cvt_native_to_s16()
207 	       data->copy_bytes);  in cvt_native_to_s16()
208 	if (data->cvt_endian)  in cvt_native_to_s16()
210 	sample ^= data->flip;  in cvt_native_to_s16()
219 	struct mulaw_priv *data = (struct mulaw_priv *)plugin->extra_data;  in mulaw_encode()
221 	int nchannels = plugin->src_format.channels;  in mulaw_encode()
229 				snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);  in mulaw_encode()
239 		while (frames1-- > 0) {  in mulaw_encode()
256 		return -ENXIO;  in mulaw_transfer()
262 		for (channel = 0; channel < plugin->src_format.channels; channel++) {  in mulaw_transfer()
265 				return -ENXIO;  in mulaw_transfer()
268 				return -ENXIO;  in mulaw_transfer()
274 	data = (struct mulaw_priv *)plugin->extra_data;  in mulaw_transfer()
275 	data->func(plugin, src_channels, dst_channels, frames);  in mulaw_transfer()
282 	data->cvt_endian = snd_pcm_format_big_endian(format) > 0;  in init_data()
284 	data->cvt_endian = snd_pcm_format_little_endian(format) > 0;  in init_data()
287 		data->flip = 0x8000;  in init_data()
288 	data->native_bytes = snd_pcm_format_physical_width(format) / 8;  in init_data()
289 	data->copy_bytes = data->native_bytes < 2 ? 1 : 2;  in init_data()
291 		data->native_ofs = data->native_bytes - data->copy_bytes;  in init_data()
292 		data->copy_ofs = 2 - data->copy_bytes;  in init_data()
295 		data->native_ofs = data->native_bytes -  in init_data()
312 		return -ENXIO;  in snd_pcm_plugin_build_mulaw()
315 	if (snd_BUG_ON(src_format->rate != dst_format->rate))  in snd_pcm_plugin_build_mulaw()
316 		return -ENXIO;  in snd_pcm_plugin_build_mulaw()
317 	if (snd_BUG_ON(src_format->channels != dst_format->channels))  in snd_pcm_plugin_build_mulaw()
318 		return -ENXIO;  in snd_pcm_plugin_build_mulaw()
320 	if (dst_format->format == SNDRV_PCM_FORMAT_MU_LAW) {  in snd_pcm_plugin_build_mulaw()
324 	else if (src_format->format == SNDRV_PCM_FORMAT_MU_LAW) {  in snd_pcm_plugin_build_mulaw()
330 		return -EINVAL;  in snd_pcm_plugin_build_mulaw()
332 	if (!snd_pcm_format_linear(format->format))  in snd_pcm_plugin_build_mulaw()
333 		return -EINVAL;  in snd_pcm_plugin_build_mulaw()
335 	err = snd_pcm_plugin_build(plug, "Mu-Law<->linear conversion",  in snd_pcm_plugin_build_mulaw()
340 	data = (struct mulaw_priv *)plugin->extra_data;  in snd_pcm_plugin_build_mulaw()
341 	data->func = func;  in snd_pcm_plugin_build_mulaw()
342 	init_data(data, format->format);  in snd_pcm_plugin_build_mulaw()
343 	plugin->transfer = mulaw_transfer;  in snd_pcm_plugin_build_mulaw()