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/*
* Copyright (c) 2012 Andrew D'Addesio
* Copyright (c) 2013-2014 Mozilla Corporation
* Copyright (c) 2016 Rostislav Pehlivanov <atomnuker@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "opus_rc.h"
static av_always_inline void opus_rc_dec_normalize(OpusRangeCoder *rc)
{
while (rc->range <= 1<<23) {
rc->value = ((rc->value << 8) | (get_bits(&rc->gb, 8) ^ 0xFF)) & ((1u << 31) - 1);
rc->range <<= 8;
rc->total_read_bits += 8;
}
}
static av_always_inline void opus_rc_dec_update(OpusRangeCoder *rc, uint32_t scale,
uint32_t low, uint32_t high,
uint32_t total)
{
rc->value -= scale * (total - high);
rc->range = low ? scale * (high - low)
: rc->range - scale * (total - high);
opus_rc_dec_normalize(rc);
}
uint32_t ff_opus_rc_dec_cdf(OpusRangeCoder *rc, const uint16_t *cdf)
{
unsigned int k, scale, total, symbol, low, high;
total = *cdf++;
scale = rc->range / total;
symbol = rc->value / scale + 1;
symbol = total - FFMIN(symbol, total);
for (k = 0; cdf[k] <= symbol; k++);
high = cdf[k];
low = k ? cdf[k-1] : 0;
opus_rc_dec_update(rc, scale, low, high, total);
return k;
}
uint32_t ff_opus_rc_dec_log(OpusRangeCoder *rc, uint32_t bits)
{
uint32_t k, scale;
scale = rc->range >> bits; // in this case, scale = symbol
if (rc->value >= scale) {
rc->value -= scale;
rc->range -= scale;
k = 0;
} else {
rc->range = scale;
k = 1;
}
opus_rc_dec_normalize(rc);
return k;
}
/**
* CELT: read 1-25 raw bits at the end of the frame, backwards byte-wise
*/
uint32_t ff_opus_rc_get_raw(OpusRangeCoder *rc, uint32_t count)
{
uint32_t value = 0;
while (rc->rb.bytes && rc->rb.cachelen < count) {
rc->rb.cacheval |= *--rc->rb.position << rc->rb.cachelen;
rc->rb.cachelen += 8;
rc->rb.bytes--;
}
value = av_mod_uintp2(rc->rb.cacheval, count);
rc->rb.cacheval >>= count;
rc->rb.cachelen -= count;
rc->total_read_bits += count;
return value;
}
/**
* CELT: read a uniform distribution
*/
uint32_t ff_opus_rc_dec_uint(OpusRangeCoder *rc, uint32_t size)
{
uint32_t bits, k, scale, total;
bits = opus_ilog(size - 1);
total = (bits > 8) ? ((size - 1) >> (bits - 8)) + 1 : size;
scale = rc->range / total;
k = rc->value / scale + 1;
k = total - FFMIN(k, total);
opus_rc_dec_update(rc, scale, k, k + 1, total);
if (bits > 8) {
k = k << (bits - 8) | ff_opus_rc_get_raw(rc, bits - 8);
return FFMIN(k, size - 1);
} else
return k;
}
uint32_t ff_opus_rc_dec_uint_step(OpusRangeCoder *rc, int k0)
{
/* Use a probability of 3 up to itheta=8192 and then use 1 after */
uint32_t k, scale, symbol, total = (k0+1)*3 + k0;
scale = rc->range / total;
symbol = rc->value / scale + 1;
symbol = total - FFMIN(symbol, total);
k = (symbol < (k0+1)*3) ? symbol/3 : symbol - (k0+1)*2;
opus_rc_dec_update(rc, scale, (k <= k0) ? 3*(k+0) : (k-1-k0) + 3*(k0+1),
(k <= k0) ? 3*(k+1) : (k-0-k0) + 3*(k0+1), total);
return k;
}
uint32_t ff_opus_rc_dec_uint_tri(OpusRangeCoder *rc, int qn)
{
uint32_t k, scale, symbol, total, low, center;
total = ((qn>>1) + 1) * ((qn>>1) + 1);
scale = rc->range / total;
center = rc->value / scale + 1;
center = total - FFMIN(center, total);
if (center < total >> 1) {
k = (ff_sqrt(8 * center + 1) - 1) >> 1;
low = k * (k + 1) >> 1;
symbol = k + 1;
} else {
k = (2*(qn + 1) - ff_sqrt(8*(total - center - 1) + 1)) >> 1;
low = total - ((qn + 1 - k) * (qn + 2 - k) >> 1);
symbol = qn + 1 - k;
}
opus_rc_dec_update(rc, scale, low, low + symbol, total);
return k;
}
int ff_opus_rc_dec_laplace(OpusRangeCoder *rc, uint32_t symbol, int decay)
{
/* extends the range coder to model a Laplace distribution */
int value = 0;
uint32_t scale, low = 0, center;
scale = rc->range >> 15;
center = rc->value / scale + 1;
center = (1 << 15) - FFMIN(center, 1 << 15);
if (center >= symbol) {
value++;
low = symbol;
symbol = 1 + ((32768 - 32 - symbol) * (16384-decay) >> 15);
while (symbol > 1 && center >= low + 2 * symbol) {
value++;
symbol *= 2;
low += symbol;
symbol = (((symbol - 2) * decay) >> 15) + 1;
}
if (symbol <= 1) {
int distance = (center - low) >> 1;
value += distance;
low += 2 * distance;
}
if (center < low + symbol)
value *= -1;
else
low += symbol;
}
opus_rc_dec_update(rc, scale, low, FFMIN(low + symbol, 32768), 32768);
return value;
}
int ff_opus_rc_dec_init(OpusRangeCoder *rc, const uint8_t *data, int size)
{
int ret = init_get_bits8(&rc->gb, data, size);
if (ret < 0)
return ret;
rc->range = 128;
rc->value = 127 - get_bits(&rc->gb, 7);
rc->total_read_bits = 9;
opus_rc_dec_normalize(rc);
return 0;
}
void ff_opus_rc_dec_raw_init(OpusRangeCoder *rc, const uint8_t *rightend, uint32_t bytes)
{
rc->rb.position = rightend;
rc->rb.bytes = bytes;
rc->rb.cachelen = 0;
rc->rb.cacheval = 0;
}
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