Use ADPCM codec on the data to/from the codec

kitsune/3200.jscope

@@ -10,7 +10,7 @@
             <DataFile Name="" />
             <RawFile Name="" />
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@@ -19,10 +19,10 @@
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kitsune/adpcm.c

@@ -0,0 +1,277 @@
+/***********************************************************
+Copyright 1992 by Stichting Mathematisch Centrum, Amsterdam, The
+Netherlands.
+
+                        All Rights Reserved
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose and without fee is hereby granted,
+provided that the above copyright notice appear in all copies and that
+both that copyright notice and this permission notice appear in
+supporting documentation, and that the names of Stichting Mathematisch
+Centrum or CWI not be used in advertising or publicity pertaining to
+distribution of the software without specific, written prior permission.
+
+STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
+THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
+FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+******************************************************************/
+
+/*
+** Intel/DVI ADPCM coder/decoder.
+**
+** The algorithm for this coder was taken from the IMA Compatability Project
+** proceedings, Vol 2, Number 2; May 1992.
+**
+** Version 1.2, 18-Dec-92.
+**
+** Change log:
+** - Fixed a stupid bug, where the delta was computed as
+**   stepsize*code/4 in stead of stepsize*(code+0.5)/4.
+** - There was an off-by-one error causing it to pick
+**   an incorrect delta once in a blue moon.
+** - The NODIVMUL define has been removed. Computations are now always done
+**   using shifts, adds and subtracts. It turned out that, because the standard
+**   is defined using shift/add/subtract, you needed bits of fixup code
+**   (because the div/mul simulation using shift/add/sub made some rounding
+**   errors that real div/mul don't make) and all together the resultant code
+**   ran slower than just using the shifts all the time.
+** - Changed some of the variable names to be more meaningful.
+*/
+
+#include "adpcm.h"
+#include <stdint.h>
+#include <stdio.h> /*DBG*/
+
+#ifndef __STDC__
+#define signed
+#endif
+
+//#define ADPCM_ENDIAN_SWAP
+
+
+#ifdef ADPCM_ENDIAN_SWAP
+uint16_t swap_uint16( uint16_t val )
+{
+	return (val << 8) | (val >> 8 );
+}
+
+//! Byte swap short
+int16_t swap_int16( int16_t val )
+{
+	return (val << 8) | ((val >> 8) & 0xFF);
+}
+#endif
+
+/* Intel ADPCM step variation table */
+static int indexTable[16] = {
+    -1, -1, -1, -1, 2, 4, 6, 8,
+    -1, -1, -1, -1, 2, 4, 6, 8,
+};
+
+static int stepsizeTable[89] = {
+    7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
+    19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
+    50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
+    130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
+    337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
+    876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
+    2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
+    5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
+    15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
+};
+
+void adpcm_coder(short *indata, char *outdata, int len, adpcm_state *state)
+{
+    short *inp;			/* Input buffer pointer */
+    signed char *outp;		/* output buffer pointer */
+    int val;			/* Current input sample value */
+    int sign;			/* Current adpcm sign bit */
+    int delta;			/* Current adpcm output value */
+    int diff;			/* Difference between val and valprev */
+    int step;			/* Stepsize */
+    int valpred;		/* Predicted output value */
+    int vpdiff;			/* Current change to valpred */
+    int index;			/* Current step change index */
+    int outputbuffer;		/* place to keep previous 4-bit value */
+    int bufferstep;		/* toggle between outputbuffer/output */
+	short tmp;
+
+    outp = (signed char *)outdata;
+    inp = indata;
+
+    valpred = state->valprev;
+    index = state->index;
+    step = stepsizeTable[index];
+
+    bufferstep = 1;
+
+    for ( ; len > 0 ; len-- ) {
+#ifdef ADPCM_ENDIAN_SWAP
+	tmp = swap_int16(*inp);
+	inp++;
+	val = tmp;
+#else
+	val = *inp++;
+#endif
+
+	/* Step 1 - compute difference with previous value */
+	diff = val - valpred;
+	sign = (diff < 0) ? 8 : 0;
+	if ( sign ) diff = (-diff);
+
+	/* Step 2 - Divide and clamp */
+	/* Note:
+	** This code *approximately* computes:
+	**    delta = diff*4/step;
+	**    vpdiff = (delta+0.5)*step/4;
+	** but in shift step bits are dropped. The net result of this is
+	** that even if you have fast mul/div hardware you cannot put it to
+	** good use since the fixup would be too expensive.
+	*/
+	delta = 0;
+	vpdiff = (step >> 3);
+
+	if ( diff >= step ) {
+	    delta = 4;
+	    diff -= step;
+	    vpdiff += step;
+	}
+	step >>= 1;
+	if ( diff >= step  ) {
+	    delta |= 2;
+	    diff -= step;
+	    vpdiff += step;
+	}
+	step >>= 1;
+	if ( diff >= step ) {
+	    delta |= 1;
+	    vpdiff += step;
+	}
+
+	/* Step 3 - Update previous value */
+	if ( sign )
+	  valpred -= vpdiff;
+	else
+	  valpred += vpdiff;
+
+	/* Step 4 - Clamp previous value to 16 bits */
+	if ( valpred > 32767 )
+	  valpred = 32767;
+	else if ( valpred < -32768 )
+	  valpred = -32768;
+
+	/* Step 5 - Assemble value, update index and step values */
+	delta |= sign;
+
+	index += indexTable[delta];
+	if ( index < 0 ) index = 0;
+	if ( index > 88 ) index = 88;
+	step = stepsizeTable[index];
+
+	/* Step 6 - Output value */
+	if ( bufferstep ) {
+	    outputbuffer = (delta << 4) & 0xf0;
+	} else {
+	    *outp++ = (delta & 0x0f) | outputbuffer;
+	}
+	bufferstep = !bufferstep;
+    }
+
+    /* Output last step, if needed */
+    if ( !bufferstep )
+      *outp++ = outputbuffer;
+
+    state->valprev = valpred;
+    state->index = index;
+}
+
+
+void adpcm_decoder(char *indata, short *outdata, int len, adpcm_state *state)
+{
+	signed char *inp;		/* Input buffer pointer */
+	short *outp;		/* output buffer pointer */
+	int sign;			/* Current adpcm sign bit */
+	int delta;			/* Current adpcm output value */
+	int step;			/* Stepsize */
+	int valpred;		/* Predicted value */
+	int vpdiff;			/* Current change to valpred */
+	int index;			/* Current step change index */
+	int inputbuffer;		/* place to keep next 4-bit value */
+	int bufferstep;		/* toggle between inputbuffer/input */
+	short tmp;
+	outp = outdata;
+	inp = (signed char *)indata;
+
+	valpred = state->valprev;
+	index = state->index;
+	step = stepsizeTable[index];
+
+	bufferstep = 0;
+
+	for ( ; len > 0 ; len-- ) {
+
+		/* Step 1 - get the delta value */
+		if ( bufferstep ) {
+			delta = inputbuffer & 0xf;
+		} else {
+			inputbuffer = *inp++;
+			delta = (inputbuffer >> 4) & 0xf;
+		}
+		bufferstep = !bufferstep;
+
+		/* Step 2 - Find new index value (for later) */
+		index += indexTable[delta];
+		if ( index < 0 ) index = 0;
+		if ( index > 88 ) index = 88;
+
+		/* Step 3 - Separate sign and magnitude */
+		sign = delta & 8;
+		delta = delta & 7;
+
+		/* Step 4 - Compute difference and new predicted value */
+		/*
+		** Computes 'vpdiff = (delta+0.5)*step/4', but see comment
+		** in adpcm_coder.
+		*/
+		vpdiff = step >> 3;
+		if ( delta & 4 ) vpdiff += step;
+		if ( delta & 2 ) vpdiff += step>>1;
+		if ( delta & 1 ) vpdiff += step>>2;
+
+		if ( sign )
+			valpred -= vpdiff;
+		else
+			valpred += vpdiff;
+
+		/* Step 5 - clamp output value */
+		if ( valpred > 32767 )
+			valpred = 32767;
+		else if ( valpred < -32768 )
+			valpred = -32768;
+
+		/* Step 6 - Update step value */
+		step = stepsizeTable[index];
+
+		/* Step 7 - Output value */
+#ifdef ADPCM_ENDIAN_SWAP
+		tmp = valpred;
+		tmp = swap_int16(tmp);
+		*outp++ = tmp;
+#else
+		*outp++ = valpred;
+#endif
+
+	}
+
+	state->valprev = valpred;
+	state->index = index;
+}
+
+
+

kitsune/adpcm.h

@@ -0,0 +1,22 @@
+/*
+** adpcm.h - include file for adpcm coder.
+**
+** Version 1.0, 7-Jul-92.
+*/
+
+#ifndef _ADPCM_H_
+#define _ADPCM_H_
+
+typedef struct adpcm_state_t {
+    short	valprev;	/* Previous output value */
+    char	index;		/* Index into stepsize table */
+}adpcm_state;
+
+
+void adpcm_coder(short *indata, char *outdata, int len, adpcm_state *state);
+
+void adpcm_decoder(char *indata, short *outdata, int len, adpcm_state *state);
+
+
+#endif
+