mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-23 12:43:46 +02:00
2503aa6bd9
* commit '0b699920f3c0b2e30969b38ce59226653f9d80ec': lagarith: Correctly compute hash_shift Merged-by: Hendrik Leppkes <h.leppkes@gmail.com>
57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
/*
|
|
* Lagarith range decoder
|
|
* Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
|
|
* Copyright (c) 2009 David Conrad
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* Lagarith range decoder
|
|
* @author Nathan Caldwell
|
|
* @author David Conrad
|
|
*/
|
|
|
|
#include "get_bits.h"
|
|
#include "lagarithrac.h"
|
|
|
|
void ff_lag_rac_init(lag_rac *l, GetBitContext *gb, int length)
|
|
{
|
|
int i, j, left;
|
|
|
|
/* According to reference decoder "1st byte is garbage",
|
|
* however, it gets skipped by the call to align_get_bits()
|
|
*/
|
|
align_get_bits(gb);
|
|
left = get_bits_left(gb) >> 3;
|
|
l->bytestream_start =
|
|
l->bytestream = gb->buffer + get_bits_count(gb) / 8;
|
|
l->bytestream_end = l->bytestream_start + left;
|
|
|
|
l->range = 0x80;
|
|
l->low = *l->bytestream >> 1;
|
|
l->hash_shift = FFMAX(l->scale, 10) - 10;
|
|
|
|
for (i = j = 0; i < 1024; i++) {
|
|
unsigned r = i << l->hash_shift;
|
|
while (l->prob[j + 1] <= r)
|
|
j++;
|
|
l->range_hash[i] = j;
|
|
}
|
|
}
|