ioef/code/client/snd_adpcm.c

/***********************************************************
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.
*/

#include "snd_local.h"


/* 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 S_AdpcmEncode( short indata[], char outdata[], int len, struct 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 sample */
    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 */

    outp = (signed char *)outdata;
    inp = indata;

    valpred = state->sample;
    index = state->index;
    step = stepsizeTable[index];
    
	outputbuffer = 0;	// quiet a compiler warning
    bufferstep = 1;

    for ( ; len > 0 ; len-- ) {
		val = *inp++;

		/* 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->sample = valpred;
    state->index = index;
}


/* static */ void S_AdpcmDecode( const char indata[], short *outdata, int len, struct adpcm_state *state ) {
    signed char *inp;		/* Input buffer pointer */
    int 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 */

    outp = 0;
    inp = (signed char *)indata;

    valpred = state->sample;
    index = state->index;
    step = stepsizeTable[index];

    bufferstep = 0;
    inputbuffer = 0;	// quiet a compiler warning
    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 */
		outdata[outp] = valpred;
		outp++;
    }

    state->sample = valpred;
    state->index = index;
}


/*
====================
S_AdpcmMemoryNeeded

Returns the amount of memory (in bytes) needed to store the samples in out internal adpcm format
====================
*/
int S_AdpcmMemoryNeeded( const wavinfo_t *info ) {
	float	scale;
	int		scaledSampleCount;
	int		sampleMemory;
	int		blockCount;
	int		headerMemory;

	// determine scale to convert from input sampling rate to desired sampling rate
	scale = (float)info->rate / dma.speed;

	// calc number of samples at playback sampling rate
	scaledSampleCount = info->samples / scale;

	// calc memory need to store those samples using ADPCM at 4 bits per sample
	sampleMemory = scaledSampleCount / 2;

	// calc number of sample blocks needed of PAINTBUFFER_SIZE
	blockCount = scaledSampleCount / PAINTBUFFER_SIZE;
	if( scaledSampleCount % PAINTBUFFER_SIZE ) {
		blockCount++;
	}

	// calc memory needed to store the block headers
	headerMemory = blockCount * sizeof(adpcm_state_t);

	return sampleMemory + headerMemory;
}


/*
====================
S_AdpcmGetSamples
====================
*/
void S_AdpcmGetSamples(sndBuffer *chunk, short *to) {
	adpcm_state_t	state;
	byte			*out;

	// get the starting state from the block header
	state.index = chunk->adpcm.index;
	state.sample = chunk->adpcm.sample;

	out = (byte *)chunk->sndChunk;
	// get samples
	S_AdpcmDecode((char *) out, to, SND_CHUNK_SIZE_BYTE*2, &state );
}


/*
====================
S_AdpcmEncodeSound
====================
*/
void S_AdpcmEncodeSound( sfx_t *sfx, short *samples ) {
	adpcm_state_t	state;
	int				inOffset;
	int				count;
	int				n;
	sndBuffer		*newchunk, *chunk;
	byte			*out;

	inOffset = 0;
	count = sfx->soundLength;
	state.index = 0;
	state.sample = samples[0];

	chunk = NULL;
	while( count ) {
		n = count;
		if( n > SND_CHUNK_SIZE_BYTE*2 ) {
			n = SND_CHUNK_SIZE_BYTE*2;
		}

		newchunk = SND_malloc();
		if (sfx->soundData == NULL) {
			sfx->soundData = newchunk;
		} else {
			chunk->next = newchunk;
		}
		chunk = newchunk;

		// output the header
		chunk->adpcm.index  = state.index;
		chunk->adpcm.sample = state.sample;

		out = (byte *)chunk->sndChunk;

		// encode the samples
		S_AdpcmEncode( samples + inOffset, (char *) out, n, &state );

		inOffset += n;
		count -= n;
	}
}