--- /dev/null
+/*
+ * 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
+ */
+
+/*
+ * g721.c
+ *
+ * Description:
+ *
+ * g721_encoder(), g721_decoder()
+ *
+ * These routines comprise an implementation of the CCITT G.721 ADPCM
+ * coding algorithm. Essentially, this implementation is identical to
+ * the bit level description except for a few deviations which
+ * take advantage of work station attributes, such as hardware 2's
+ * complement arithmetic and large memory. Specifically, certain time
+ * consuming operations such as multiplications are replaced
+ * with lookup tables and software 2's complement operations are
+ * replaced with hardware 2's complement.
+ *
+ * The deviation from the bit level specification (lookup tables)
+ * preserves the bit level performance specifications.
+ *
+ * As outlined in the G.721 Recommendation, the algorithm is broken
+ * down into modules. Each section of code below is preceded by
+ * the name of the module which it is implementing.
+ *
+ */
+
+#include "g72x.h"
+#include "g72x_priv.h"
+
+static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
+/*
+ * Maps G.721 code word to reconstructed scale factor normalized log
+ * magnitude values.
+ */
+static short _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
+ 425, 373, 323, 273, 213, 135, 4, -2048};
+
+/* Maps G.721 code word to log of scale factor multiplier. */
+static short _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
+ 1122, 355, 198, 112, 64, 41, 18, -12};
+/*
+ * Maps G.721 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[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
+ 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
+
+/*
+ * g721_encoder()
+ *
+ * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
+ * the resulting code. -1 is returned for unknown input coding value.
+ */
+int
+g721_encoder(
+ int sl,
+ G72x_STATE *state_ptr)
+{
+ short sezi, se, sez; /* ACCUM */
+ short d; /* SUBTA */
+ short sr; /* ADDB */
+ short y; /* MIX */
+ short dqsez; /* ADDC */
+ short dq, i;
+
+ /* linearize input sample to 14-bit PCM */
+ sl >>= 2; /* 14-bit dynamic range */
+
+ sezi = predictor_zero(state_ptr);
+ sez = sezi >> 1;
+ se = (sezi + predictor_pole(state_ptr)) >> 1; /* estimated signal */
+
+ d = sl - se; /* estimation difference */
+
+ /* quantize the prediction difference */
+ y = step_size(state_ptr); /* quantizer step size */
+ i = quantize(d, y, qtab_721, 7); /* i = ADPCM code */
+
+ dq = reconstruct(i & 8, _dqlntab[i], y); /* quantized est diff */
+
+ sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconst. signal */
+
+ dqsez = sr + sez - se; /* pole prediction diff. */
+
+ update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
+
+ return (i);
+}
+
+/*
+ * g721_decoder()
+ *
+ * Description:
+ *
+ * Decodes a 4-bit code of G.721 encoded data of i and
+ * returns the resulting linear PCM, A-law or u-law value.
+ * return -1 for unknown out_coding value.
+ */
+int
+g721_decoder(
+ int i,
+ G72x_STATE *state_ptr)
+{
+ short sezi, sei, sez, se; /* ACCUM */
+ short y; /* MIX */
+ short sr; /* ADDB */
+ short dq;
+ short dqsez;
+
+ i &= 0x0f; /* 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); /* dynamic quantizer step size */
+
+ dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
+
+ sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */
+
+ dqsez = sr - se + sez; /* pole prediction diff. */
+
+ update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
+
+ /* sr was 14-bit dynamic range */
+ return (sr << 2);
+}
+
projects / Faustine.git / blobdiff