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408 lines
13 KiB
C
408 lines
13 KiB
C
////////////////////////////////////////////////////////////////////////////
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// **** ADPCM-XQ **** //
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// Xtreme Quality ADPCM Encoder/Decoder //
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// Copyright (c) 2022 David Bryant. //
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// All Rights Reserved. //
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// Distributed under the BSD Software License (see license.txt) //
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////////////////////////////////////////////////////////////////////////////
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#include <stdlib.h>
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#include <string.h>
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#include "adpcm-lib.h"
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/* This module encodes and decodes 4-bit ADPCM (DVI/IMA varient). ADPCM data is divided
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* into independently decodable blocks that can be relatively small. The most common
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* configuration is to store 505 samples into a 256 byte block, although other sizes are
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* permitted as long as the number of samples is one greater than a multiple of 8. When
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* multiple channels are present, they are interleaved in the data with an 8-sample
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* interval.
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*/
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/********************************* 4-bit ADPCM encoder ********************************/
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#define CLIP(data, min, max) \
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if ((data) > (max)) data = max; \
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else if ((data) < (min)) data = min;
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/* step table */
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static const uint16_t step_table[89] = {
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7, 8, 9, 10, 11, 12, 13, 14,
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16, 17, 19, 21, 23, 25, 28, 31,
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34, 37, 41, 45, 50, 55, 60, 66,
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73, 80, 88, 97, 107, 118, 130, 143,
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157, 173, 190, 209, 230, 253, 279, 307,
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337, 371, 408, 449, 494, 544, 598, 658,
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724, 796, 876, 963, 1060, 1166, 1282, 1411,
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1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
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3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
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7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
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15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
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32767
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};
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/* step index tables */
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static const int index_table[] = {
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/* adpcm data size is 4 */
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-1, -1, -1, -1, 2, 4, 6, 8
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};
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struct adpcm_channel {
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int32_t pcmdata; // current PCM value
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int32_t error, weight, history [2]; // for noise shaping
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int8_t index; // current index into step size table
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};
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struct adpcm_context {
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struct adpcm_channel channels [2];
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int num_channels, lookahead, noise_shaping;
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};
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/* Create ADPCM encoder context with given number of channels.
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* The returned pointer is used for subsequent calls. Note that
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* even though an ADPCM encoder could be set up to encode frames
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* independently, we use a context so that we can use previous
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* data to improve quality (this encoder might not be optimal
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* for encoding independent frames).
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*/
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void *adpcm_create_context (int num_channels, int lookahead, int noise_shaping, int32_t initial_deltas [2])
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{
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struct adpcm_context *pcnxt = malloc (sizeof (struct adpcm_context));
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int ch, i;
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memset (pcnxt, 0, sizeof (struct adpcm_context));
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pcnxt->noise_shaping = noise_shaping;
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pcnxt->num_channels = num_channels;
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pcnxt->lookahead = lookahead;
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// given the supplied initial deltas, search for and store the closest index
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for (ch = 0; ch < num_channels; ++ch)
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for (i = 0; i <= 88; i++)
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if (i == 88 || initial_deltas [ch] < ((int32_t) step_table [i] + step_table [i+1]) / 2) {
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pcnxt->channels [ch].index = i;
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break;
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}
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return pcnxt;
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}
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/* Free the ADPCM encoder context.
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*/
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void adpcm_free_context (void *p)
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{
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struct adpcm_context *pcnxt = (struct adpcm_context *) p;
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free (pcnxt);
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}
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static void set_decode_parameters (struct adpcm_context *pcnxt, int32_t *init_pcmdata, int8_t *init_index)
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{
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int ch;
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for (ch = 0; ch < pcnxt->num_channels; ch++) {
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pcnxt->channels[ch].pcmdata = init_pcmdata[ch];
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pcnxt->channels[ch].index = init_index[ch];
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}
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}
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static void get_decode_parameters (struct adpcm_context *pcnxt, int32_t *init_pcmdata, int8_t *init_index)
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{
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int ch;
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for (ch = 0; ch < pcnxt->num_channels; ch++) {
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init_pcmdata[ch] = pcnxt->channels[ch].pcmdata;
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init_index[ch] = pcnxt->channels[ch].index;
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}
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}
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static double minimum_error (const struct adpcm_channel *pchan, int nch, int32_t csample, const int16_t *sample, int depth, int *best_nibble)
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{
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int32_t delta = csample - pchan->pcmdata;
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struct adpcm_channel chan = *pchan;
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uint16_t step = step_table[chan.index];
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uint16_t trial_delta = (step >> 3);
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int nibble, nibble2;
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double min_error;
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if (delta < 0) {
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int mag = (-delta << 2) / step;
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nibble = 0x8 | (mag > 7 ? 7 : mag);
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}
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else {
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int mag = (delta << 2) / step;
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nibble = mag > 7 ? 7 : mag;
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}
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if (nibble & 1) trial_delta += (step >> 2);
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if (nibble & 2) trial_delta += (step >> 1);
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if (nibble & 4) trial_delta += step;
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if (nibble & 8)
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chan.pcmdata -= trial_delta;
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else
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chan.pcmdata += trial_delta;
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CLIP(chan.pcmdata, -32768, 32767);
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if (best_nibble) *best_nibble = nibble;
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min_error = (double) (chan.pcmdata - csample) * (chan.pcmdata - csample);
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if (depth) {
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chan.index += index_table[nibble & 0x07];
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CLIP(chan.index, 0, 88);
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min_error += minimum_error (&chan, nch, sample [nch], sample + nch, depth - 1, NULL);
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}
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else
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return min_error;
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for (nibble2 = 0; nibble2 <= 0xF; ++nibble2) {
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double error;
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if (nibble2 == nibble)
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continue;
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chan = *pchan;
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trial_delta = (step >> 3);
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if (nibble2 & 1) trial_delta += (step >> 2);
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if (nibble2 & 2) trial_delta += (step >> 1);
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if (nibble2 & 4) trial_delta += step;
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if (nibble2 & 8)
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chan.pcmdata -= trial_delta;
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else
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chan.pcmdata += trial_delta;
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CLIP(chan.pcmdata, -32768, 32767);
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error = (double) (chan.pcmdata - csample) * (chan.pcmdata - csample);
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if (error < min_error) {
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chan.index += index_table[nibble2 & 0x07];
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CLIP(chan.index, 0, 88);
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error += minimum_error (&chan, nch, sample [nch], sample + nch, depth - 1, NULL);
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if (error < min_error) {
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if (best_nibble) *best_nibble = nibble2;
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min_error = error;
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}
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}
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}
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return min_error;
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}
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static uint8_t encode_sample (struct adpcm_context *pcnxt, int ch, const int16_t *sample, int num_samples)
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{
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struct adpcm_channel *pchan = pcnxt->channels + ch;
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int32_t csample = *sample;
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int depth = num_samples - 1, nibble;
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uint16_t step = step_table[pchan->index];
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uint16_t trial_delta = (step >> 3);
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if (pcnxt->noise_shaping == NOISE_SHAPING_DYNAMIC) {
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int32_t sam = (3 * pchan->history [0] - pchan->history [1]) >> 1;
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int32_t temp = csample - (((pchan->weight * sam) + 512) >> 10);
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int32_t shaping_weight;
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if (sam && temp) pchan->weight -= (((sam ^ temp) >> 29) & 4) - 2;
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pchan->history [1] = pchan->history [0];
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pchan->history [0] = csample;
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shaping_weight = (pchan->weight < 256) ? 1024 : 1536 - (pchan->weight * 2);
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temp = -((shaping_weight * pchan->error + 512) >> 10);
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if (shaping_weight < 0 && temp) {
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if (temp == pchan->error)
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temp = (temp < 0) ? temp + 1 : temp - 1;
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pchan->error = -csample;
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csample += temp;
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}
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else
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pchan->error = -(csample += temp);
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}
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else if (pcnxt->noise_shaping == NOISE_SHAPING_STATIC)
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pchan->error = -(csample -= pchan->error);
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if (depth > pcnxt->lookahead)
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depth = pcnxt->lookahead;
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minimum_error (pchan, pcnxt->num_channels, csample, sample, depth, &nibble);
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if (nibble & 1) trial_delta += (step >> 2);
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if (nibble & 2) trial_delta += (step >> 1);
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if (nibble & 4) trial_delta += step;
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if (nibble & 8)
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pchan->pcmdata -= trial_delta;
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else
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pchan->pcmdata += trial_delta;
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pchan->index += index_table[nibble & 0x07];
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CLIP(pchan->index, 0, 88);
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CLIP(pchan->pcmdata, -32768, 32767);
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if (pcnxt->noise_shaping)
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pchan->error += pchan->pcmdata;
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return nibble;
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}
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static void encode_chunks (struct adpcm_context *pcnxt, uint8_t **outbuf, size_t *outbufsize, const int16_t **inbuf, int inbufcount)
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{
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const int16_t *pcmbuf;
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int chunks, ch, i;
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chunks = (inbufcount - 1) / 8;
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*outbufsize += (chunks * 4) * pcnxt->num_channels;
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while (chunks--)
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{
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for (ch = 0; ch < pcnxt->num_channels; ch++)
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{
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pcmbuf = *inbuf + ch;
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for (i = 0; i < 4; i++) {
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**outbuf = encode_sample (pcnxt, ch, pcmbuf, chunks * 8 + (3 - i) * 2 + 2);
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pcmbuf += pcnxt->num_channels;
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**outbuf |= encode_sample (pcnxt, ch, pcmbuf, chunks * 8 + (3 - i) * 2 + 1) << 4;
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pcmbuf += pcnxt->num_channels;
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(*outbuf)++;
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}
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}
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*inbuf += 8 * pcnxt->num_channels;
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}
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}
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/* Encode a block of 16-bit PCM data into 4-bit ADPCM.
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*
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* Parameters:
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* p the context returned by adpcm_begin()
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* outbuf destination buffer
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* outbufsize pointer to variable where the number of bytes written
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* will be stored
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* inbuf source PCM samples
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* inbufcount number of composite PCM samples provided (note: this is
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* the total number of 16-bit samples divided by the number
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* of channels)
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*
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* Returns 1 (for success as there is no error checking)
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*/
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int adpcm_encode_block (void *p, uint8_t *outbuf, size_t *outbufsize, const int16_t *inbuf, int inbufcount)
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{
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struct adpcm_context *pcnxt = (struct adpcm_context *) p;
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int32_t init_pcmdata[2];
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int8_t init_index[2];
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int ch;
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*outbufsize = 0;
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if (!inbufcount)
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return 1;
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get_decode_parameters(pcnxt, init_pcmdata, init_index);
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for (ch = 0; ch < pcnxt->num_channels; ch++) {
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init_pcmdata[ch] = *inbuf++;
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outbuf[0] = init_pcmdata[ch];
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outbuf[1] = init_pcmdata[ch] >> 8;
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outbuf[2] = init_index[ch];
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outbuf[3] = 0;
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outbuf += 4;
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*outbufsize += 4;
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}
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set_decode_parameters(pcnxt, init_pcmdata, init_index);
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encode_chunks (pcnxt, &outbuf, outbufsize, &inbuf, inbufcount);
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return 1;
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}
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/********************************* 4-bit ADPCM decoder ********************************/
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/* Decode the block of ADPCM data into PCM. This requires no context because ADPCM blocks
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* are indeppendently decodable. This assumes that a single entire block is always decoded;
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* it must be called multiple times for multiple blocks and cannot resume in the middle of a
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* block.
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*
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* Parameters:
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* outbuf destination for interleaved PCM samples
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* inbuf source ADPCM block
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* inbufsize size of source ADPCM block
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* channels number of channels in block (must be determined from other context)
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*
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* Returns number of converted composite samples (total samples divided by number of channels)
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*/
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int adpcm_decode_block (int16_t *outbuf, const uint8_t *inbuf, size_t inbufsize, size_t outbufsize)
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{
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int samples = 1, chunks;
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int32_t pcmdata[2];
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int8_t index[2];
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if (inbufsize < 4)
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return 0;
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*outbuf++ = pcmdata[0] = (int16_t) (inbuf [0] | (inbuf [1] << 8));
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index[0] = inbuf [2];
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if (index [0] < 0 || index [0] > 88 || inbuf [3]) // sanitize the input a little...
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return 0;
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inbufsize -= 4;
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inbuf += 4;
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chunks = inbufsize / 4;
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samples += chunks * 8;
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while (chunks--) {
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int i;
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for (i = 0; i < 4; ++i) {
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uint16_t step = step_table [index [0]], delta = step >> 3;
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if (*inbuf & 1) delta += (step >> 2);
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if (*inbuf & 2) delta += (step >> 1);
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if (*inbuf & 4) delta += step;
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if (*inbuf & 8)
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pcmdata[0] -= delta;
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else
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pcmdata[0] += delta;
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index[0] += index_table [*inbuf & 0x7];
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CLIP(index[0], 0, 88);
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CLIP(pcmdata[0], -32768, 32767);
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outbuf [i * 2] = pcmdata[0];
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step = step_table [index [0]]; delta = step >> 3;
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if (*inbuf & 0x10) delta += (step >> 2);
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if (*inbuf & 0x20) delta += (step >> 1);
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if (*inbuf & 0x40) delta += step;
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if (*inbuf & 0x80)
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pcmdata[0] -= delta;
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else
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pcmdata[0] += delta;
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index[0] += index_table [(*inbuf >> 4) & 0x7];
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CLIP(index[0], 0, 88);
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CLIP(pcmdata[0], -32768, 32767);
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outbuf [(i * 2 + 1)] = pcmdata[0];
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inbuf++;
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}
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outbuf += 8;
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}
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return samples;
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}
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