mirror of https://github.com/FFmpeg/FFmpeg.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
74 lines
1.7 KiB
74 lines
1.7 KiB
/* |
|
* bitstream.c |
|
* |
|
* Copyright (C) Aaron Holtzman - Dec 1999 |
|
* |
|
* This file is part of ac3dec, a free AC-3 audio decoder |
|
* |
|
* ac3dec is free software; you can redistribute it and/or modify |
|
* it under the terms of the GNU General Public License as published by |
|
* the Free Software Foundation; either version 2, or (at your option) |
|
* any later version. |
|
* |
|
* ac3dec 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 General Public License for more details. |
|
* |
|
* You should have received a copy of the GNU General Public License |
|
* along with GNU Make; see the file COPYING. If not, write to |
|
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. |
|
* |
|
*/ |
|
|
|
#include "../common.h" |
|
#include "ac3.h" |
|
#include "ac3_internal.h" |
|
#include "bitstream.h" |
|
|
|
#define BUFFER_SIZE 4096 |
|
|
|
static uint8_t *buffer_start; |
|
|
|
uint32_t bits_left; |
|
uint32_t current_word; |
|
|
|
void bitstream_set_ptr (uint8_t * buf) |
|
{ |
|
buffer_start = buf; |
|
bits_left = 0; |
|
} |
|
|
|
static inline void |
|
bitstream_fill_current() |
|
{ |
|
current_word = *((uint32_t*)buffer_start)++; |
|
current_word = swab32(current_word); |
|
} |
|
|
|
// |
|
// The fast paths for _get is in the |
|
// bitstream.h header file so it can be inlined. |
|
// |
|
// The "bottom half" of this routine is suffixed _bh |
|
// |
|
// -ah |
|
// |
|
|
|
uint32_t |
|
bitstream_get_bh(uint32_t num_bits) |
|
{ |
|
uint32_t result; |
|
|
|
num_bits -= bits_left; |
|
result = (current_word << (32 - bits_left)) >> (32 - bits_left); |
|
|
|
bitstream_fill_current(); |
|
|
|
if(num_bits != 0) |
|
result = (result << num_bits) | (current_word >> (32 - num_bits)); |
|
|
|
bits_left = 32 - num_bits; |
|
|
|
return result; |
|
}
|
|
|