mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-11-21 10:55:51 +02:00
100 lines
2.4 KiB
C
100 lines
2.4 KiB
C
/*
|
|
* bitstream.c
|
|
* Copyright (C) 2000-2002 Michel Lespinasse <walken@zoy.org>
|
|
* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
|
|
*
|
|
* This file is part of a52dec, a free ATSC A-52 stream decoder.
|
|
* See http://liba52.sourceforge.net/ for updates.
|
|
*
|
|
* a52dec 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 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* a52dec 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 this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
*/
|
|
|
|
#include "a52.h"
|
|
#include "a52_internal.h"
|
|
#include "bitstream.h"
|
|
|
|
#define BUFFER_SIZE 4096
|
|
|
|
static uint32_t * buffer_start;
|
|
|
|
uint32_t a52_bits_left;
|
|
uint32_t a52_current_word;
|
|
|
|
void a52_bitstream_set_ptr (uint8_t * buf)
|
|
{
|
|
int align;
|
|
|
|
align = (long)buf & 3;
|
|
buffer_start = (uint32_t *) (buf - align);
|
|
a52_bits_left = 0;
|
|
bitstream_get (align * 8);
|
|
}
|
|
|
|
static inline void
|
|
bitstream_fill_current()
|
|
{
|
|
uint32_t tmp;
|
|
|
|
tmp = *(buffer_start++);
|
|
a52_current_word = swab32 (tmp);
|
|
}
|
|
|
|
/*
|
|
* 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
|
|
a52_bitstream_get_bh(uint32_t num_bits)
|
|
{
|
|
uint32_t result;
|
|
|
|
num_bits -= a52_bits_left;
|
|
result = ((a52_current_word << (32 - a52_bits_left)) >>
|
|
(32 - a52_bits_left));
|
|
|
|
bitstream_fill_current();
|
|
|
|
if(num_bits != 0)
|
|
result = (result << num_bits) | (a52_current_word >> (32 - num_bits));
|
|
|
|
a52_bits_left = 32 - num_bits;
|
|
|
|
return result;
|
|
}
|
|
|
|
int32_t
|
|
a52_bitstream_get_bh_2(uint32_t num_bits)
|
|
{
|
|
int32_t result;
|
|
|
|
num_bits -= a52_bits_left;
|
|
result = ((((int32_t)a52_current_word) << (32 - a52_bits_left)) >>
|
|
(32 - a52_bits_left));
|
|
|
|
bitstream_fill_current();
|
|
|
|
if(num_bits != 0)
|
|
result = (result << num_bits) | (a52_current_word >> (32 - num_bits));
|
|
|
|
a52_bits_left = 32 - num_bits;
|
|
|
|
return result;
|
|
}
|