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+/*
+ * This source code is a product of Sun Microsystems, Inc. and is provided
+ * for unrestricted use. Users may copy or modify this source code without
+ * charge.
+ *
+ * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
+ * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
+ *
+ * Sun source code is provided with no support and without any obligation on
+ * the part of Sun Microsystems, Inc. to assist in its use, correction,
+ * modification or enhancement.
+ *
+ * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
+ * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
+ * OR ANY PART THEREOF.
+ *
+ * In no event will Sun Microsystems, Inc. be liable for any lost revenue
+ * or profits or other special, indirect and consequential damages, even if
+ * Sun has been advised of the possibility of such damages.
+ *
+ * Sun Microsystems, Inc.
+ * 2550 Garcia Avenue
+ * Mountain View, California 94043
+ */
+
+/*
+ * g723_24.c
+ *
+ * Description:
+ *
+ * g723_24_encoder(), g723_24_decoder()
+ *
+ * These routines comprise an implementation of the CCITT G.723 24 Kbps
+ * ADPCM coding algorithm. Essentially, this implementation is identical to
+ * the bit level description except for a few deviations which take advantage
+ * of workstation attributes, such as hardware 2's complement arithmetic.
+ *
+ */
+#include "g72x.h"
+
+/*
+ * Maps G.723_24 code word to reconstructed scale factor normalized log
+ * magnitude values.
+ */
+static short _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
+
+/* Maps G.723_24 code word to log of scale factor multiplier. */
+static short _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
+
+/*
+ * Maps G.723_24 code words to a set of values whose long and short
+ * term averages are computed and then compared to give an indication
+ * how stationary (steady state) the signal is.
+ */
+static short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
+
+static short qtab_723_24[3] = {8, 218, 331};
+
+/*
+ * g723_24_encoder()
+ *
+ * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
+ * Returns -1 if invalid input coding value.
+ */
+int
+g723_24_encoder(
+ int sl,
+ int in_coding,
+ struct g72x_state *state_ptr)
+{
+ short sei, sezi, se, sez; /* ACCUM */
+ short d; /* SUBTA */
+ short y; /* MIX */
+ short sr; /* ADDB */
+ short dqsez; /* ADDC */
+ short dq, i;
+
+ switch (in_coding) { /* linearize input sample to 14-bit PCM */
+ case AUDIO_ENCODING_ALAW:
+ sl = alaw2linear(sl) >> 2;
+ break;
+ case AUDIO_ENCODING_ULAW:
+ sl = ulaw2linear(sl) >> 2;
+ break;
+ case AUDIO_ENCODING_LINEAR:
+ sl >>= 2; /* sl of 14-bit dynamic range */
+ break;
+ default:
+ return (-1);
+ }
+
+ sezi = predictor_zero(state_ptr);
+ sez = sezi >> 1;
+ sei = sezi + predictor_pole(state_ptr);
+ se = sei >> 1; /* se = estimated signal */
+
+ d = sl - se; /* d = estimation diff. */
+
+ /* quantize prediction difference d */
+ y = step_size(state_ptr); /* quantizer step size */
+ i = quantize(d, y, qtab_723_24, 3); /* i = ADPCM code */
+ dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
+
+ sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
+
+ dqsez = sr + sez - se; /* pole prediction diff. */
+
+ update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
+
+ return (i);
+}
+
+/*
+ * g723_24_decoder()
+ *
+ * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
+ * the resulting 16-bit linear PCM, A-law or u-law sample value.
+ * -1 is returned if the output coding is unknown.
+ */
+int
+g723_24_decoder(
+ int i,
+ int out_coding,
+ struct g72x_state *state_ptr)
+{
+ short sezi, sei, sez, se; /* ACCUM */
+ short y; /* MIX */
+ short sr; /* ADDB */
+ short dq;
+ short dqsez;
+
+ i &= 0x07; /* mask to get proper bits */
+ sezi = predictor_zero(state_ptr);
+ sez = sezi >> 1;
+ sei = sezi + predictor_pole(state_ptr);
+ se = sei >> 1; /* se = estimated signal */
+
+ y = step_size(state_ptr); /* adaptive quantizer step size */
+ dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
+
+ sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
+
+ dqsez = sr - se + sez; /* pole prediction diff. */
+
+ update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
+
+ switch (out_coding) {
+ case AUDIO_ENCODING_ALAW:
+ return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24));
+ case AUDIO_ENCODING_ULAW:
+ return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24));
+ case AUDIO_ENCODING_LINEAR:
+ return (sr << 2); /* sr was of 14-bit dynamic range */
+ default:
+ return (-1);
+ }
+}