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| /*
| *
| * Copyright 2015 Rockchip Electronics Co. LTD
| *
| * Licensed under the Apache License, Version 2.0 (the "License");
| * you may not use this file except in compliance with the License.
| * You may obtain a copy of the License at
| *
| * http://www.apache.org/licenses/LICENSE-2.0
| *
| * Unless required by applicable law or agreed to in writing, software
| * distributed under the License is distributed on an "AS IS" BASIS,
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
| * See the License for the specific language governing permissions and
| * limitations under the License.
| */
|
|
| #include "vpx_rac.h"
|
| #define DEF( name, bytes, read, write) \
| static unsigned int bytestream_get_ ## name(const uint8_t **b) \
| { \
| (*b) += bytes; \
| return read(*b - bytes); \
| }
|
| DEF(be24, 3, MPP_RB24, MPP_WB24)
| DEF(be16, 2, MPP_RB16, MPP_WB16)
|
| const uint8_t vpx_norm_shift[256] = {
| 8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
| 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
| 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
| 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
| 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
| 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
| 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
| 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
| };
|
| void vpx_init_range_decoder(VpxRangeCoder *c, const uint8_t *buf, int buf_size)
| {
| c->high = 255;
| c->bits = -16;
| c->buffer = buf;
| c->end = buf + buf_size;
| c->code_word = bytestream_get_be24(&c->buffer);
| }
|
| unsigned int vpx_rac_renorm(VpxRangeCoder *c)
| {
| int shift = vpx_norm_shift[c->high];
| int bits = c->bits;
| unsigned int code_word = c->code_word;
|
| c->high <<= shift;
| code_word <<= shift;
| bits += shift;
| if (bits >= 0 && c->buffer < c->end) {
| code_word |= bytestream_get_be16(&c->buffer) << bits;
| bits -= 16;
| }
| c->bits = bits;
| return code_word;
| }
|
| int vpx_rac_get_prob(VpxRangeCoder *c, uint8_t prob)
| {
| unsigned int code_word = vpx_rac_renorm(c);
| unsigned int low = 1 + (((c->high - 1) * prob) >> 8);
| unsigned int low_shift = low << 16;
| int bit = code_word >= low_shift;
|
| c->high = bit ? c->high - low : low;
| c->code_word = bit ? code_word - low_shift : code_word;
|
| return bit;
| }
|
| // branchy variant, to be used where there's a branch based on the bit decoded
| int vpx_rac_get_prob_branchy(VpxRangeCoder *c, int prob)
| {
| unsigned long code_word = vpx_rac_renorm(c);
| unsigned low = 1 + (((c->high - 1) * prob) >> 8);
| unsigned low_shift = low << 16;
|
| if (code_word >= low_shift) {
| c->high -= low;
| c->code_word = code_word - low_shift;
| return 1;
| }
|
| c->high = low;
| c->code_word = code_word;
| return 0;
| }
|
| // rounding is different than vpx_rac_get, is vpx_rac_get wrong?
| int vpx_rac_get(VpxRangeCoder *c)
| {
| return vpx_rac_get_prob(c, 128);
| }
|
| int vpx_rac_get_uint(VpxRangeCoder *c, int bits)
| {
| int value = 0;
|
| while (bits--) {
| value = (value << 1) | vpx_rac_get(c);
| }
|
| return value;
| }
|
|
