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FFmpeg/libavcodec/mpeg12.c
Andreas Rheinhardt 7e2120c4d9 avcodec/mpeg12: Avoid unnecessary VLC structures 
Everything besides VLC.table is basically write-only
and even VLC.table can be removed by accessing the
underlying tables directly.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2023-10-31 21:44:48 +01:00

264 lines
8.3 KiB
C
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/*
* MPEG-1/2 decoder
* Copyright (c) 2000, 2001 Fabrice Bellard
* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
*
* 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
* MPEG-1/2 decoder
*/
#define UNCHECKED_BITSTREAM_READER 1
#include "libavutil/attributes.h"
#include "libavutil/avassert.h"
#include "libavutil/thread.h"
#include "avcodec.h"
#include "mpegvideo.h"
#include "mpeg12.h"
#include "mpeg12codecs.h"
#include "mpeg12data.h"
#include "mpeg12dec.h"
#include "rl.h"
#include "startcode.h"
static const uint8_t table_mb_ptype[7][2] = {
{ 3, 5 }, // 0x01 MB_INTRA
{ 1, 2 }, // 0x02 MB_PAT
{ 1, 3 }, // 0x08 MB_FOR
{ 1, 1 }, // 0x0A MB_FOR|MB_PAT
{ 1, 6 }, // 0x11 MB_QUANT|MB_INTRA
{ 1, 5 }, // 0x12 MB_QUANT|MB_PAT
{ 2, 5 }, // 0x1A MB_QUANT|MB_FOR|MB_PAT
};
static const uint8_t table_mb_btype[11][2] = {
{ 3, 5 }, // 0x01 MB_INTRA
{ 2, 3 }, // 0x04 MB_BACK
{ 3, 3 }, // 0x06 MB_BACK|MB_PAT
{ 2, 4 }, // 0x08 MB_FOR
{ 3, 4 }, // 0x0A MB_FOR|MB_PAT
{ 2, 2 }, // 0x0C MB_FOR|MB_BACK
{ 3, 2 }, // 0x0E MB_FOR|MB_BACK|MB_PAT
{ 1, 6 }, // 0x11 MB_QUANT|MB_INTRA
{ 2, 6 }, // 0x16 MB_QUANT|MB_BACK|MB_PAT
{ 3, 6 }, // 0x1A MB_QUANT|MB_FOR|MB_PAT
{ 2, 5 }, // 0x1E MB_QUANT|MB_FOR|MB_BACK|MB_PAT
};
av_cold void ff_init_2d_vlc_rl(const uint16_t table_vlc[][2], RL_VLC_ELEM rl_vlc[],
const int8_t table_run[], const uint8_t table_level[],
int n, unsigned static_size, int flags)
{
int i;
VLCElem table[680] = { 0 };
VLC vlc = { .table = table, .table_allocated = static_size };
av_assert0(static_size <= FF_ARRAY_ELEMS(table));
vlc_init(&vlc, TEX_VLC_BITS, n + 2, &table_vlc[0][1], 4, 2, &table_vlc[0][0], 4, 2, VLC_INIT_USE_STATIC | flags);
for (i = 0; i < vlc.table_size; i++) {
int code = vlc.table[i].sym;
int len = vlc.table[i].len;
int level, run;
if (len == 0) { // illegal code
run = 65;
level = MAX_LEVEL;
} else if (len<0) { //more bits needed
run = 0;
level = code;
} else {
if (code == n) { //esc
run = 65;
level = 0;
} else if (code == n + 1) { //eob
run = 0;
level = 127;
} else {
run = table_run [code] + 1;
level = table_level[code];
}
}
rl_vlc[i].len = len;
rl_vlc[i].level = level;
rl_vlc[i].run = run;
}
}
void ff_mpeg1_clean_buffers(MpegEncContext *s)
{
s->last_dc[0] = 1 << (7 + s->intra_dc_precision);
s->last_dc[1] = s->last_dc[0];
s->last_dc[2] = s->last_dc[0];
memset(s->last_mv, 0, sizeof(s->last_mv));
}
/******************************************/
/* decoding */
VLCElem ff_mv_vlc[266];
VLCElem ff_dc_lum_vlc[512];
VLCElem ff_dc_chroma_vlc[514];
VLCElem ff_mbincr_vlc[538];
VLCElem ff_mb_ptype_vlc[64];
VLCElem ff_mb_btype_vlc[64];
VLCElem ff_mb_pat_vlc[512];
RL_VLC_ELEM ff_mpeg1_rl_vlc[680];
RL_VLC_ELEM ff_mpeg2_rl_vlc[674];
static av_cold void mpeg12_init_vlcs(void)
{
VLC_INIT_STATIC_TABLE(ff_dc_lum_vlc, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_lum_bits, 1, 1,
ff_mpeg12_vlc_dc_lum_code, 2, 2, 0);
VLC_INIT_STATIC_TABLE(ff_dc_chroma_vlc, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_chroma_bits, 1, 1,
ff_mpeg12_vlc_dc_chroma_code, 2, 2, 0);
VLC_INIT_STATIC_TABLE(ff_mv_vlc, MV_VLC_BITS, 17,
&ff_mpeg12_mbMotionVectorTable[0][1], 2, 1,
&ff_mpeg12_mbMotionVectorTable[0][0], 2, 1, 0);
VLC_INIT_STATIC_TABLE(ff_mbincr_vlc, MBINCR_VLC_BITS, 36,
&ff_mpeg12_mbAddrIncrTable[0][1], 2, 1,
&ff_mpeg12_mbAddrIncrTable[0][0], 2, 1, 0);
VLC_INIT_STATIC_TABLE(ff_mb_pat_vlc, MB_PAT_VLC_BITS, 64,
&ff_mpeg12_mbPatTable[0][1], 2, 1,
&ff_mpeg12_mbPatTable[0][0], 2, 1, 0);
VLC_INIT_STATIC_TABLE(ff_mb_ptype_vlc, MB_PTYPE_VLC_BITS, 7,
&table_mb_ptype[0][1], 2, 1,
&table_mb_ptype[0][0], 2, 1, 0);
VLC_INIT_STATIC_TABLE(ff_mb_btype_vlc, MB_BTYPE_VLC_BITS, 11,
&table_mb_btype[0][1], 2, 1,
&table_mb_btype[0][0], 2, 1, 0);
ff_init_2d_vlc_rl(ff_mpeg1_vlc_table, ff_mpeg1_rl_vlc, ff_mpeg12_run,
ff_mpeg12_level, MPEG12_RL_NB_ELEMS,
FF_ARRAY_ELEMS(ff_mpeg1_rl_vlc), 0);
ff_init_2d_vlc_rl(ff_mpeg2_vlc_table, ff_mpeg2_rl_vlc, ff_mpeg12_run,
ff_mpeg12_level, MPEG12_RL_NB_ELEMS,
FF_ARRAY_ELEMS(ff_mpeg2_rl_vlc), 0);
}
av_cold void ff_mpeg12_init_vlcs(void)
{
static AVOnce init_static_once = AV_ONCE_INIT;
ff_thread_once(&init_static_once, mpeg12_init_vlcs);
}
#define MAX_INDEX (64 - 1)
int ff_mpeg1_decode_block_intra(GetBitContext *gb,
const uint16_t *quant_matrix,
const uint8_t *scantable, int last_dc[3],
int16_t *block, int index, int qscale)
{
int dc, diff, i = 0, component;
/* DC coefficient */
component = index <= 3 ? 0 : index - 4 + 1;
diff = decode_dc(gb, component);
if (diff >= 0xffff)
return AVERROR_INVALIDDATA;
dc = last_dc[component];
dc += diff;
last_dc[component] = dc;
block[0] = dc * quant_matrix[0];
{
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
if (((int32_t)GET_CACHE(re, gb)) <= (int32_t)0xBFFFFFFF)
goto end;
/* now quantify & encode AC coefficients */
while (1) {
int level, run, j;
GET_RL_VLC(level, run, re, gb, ff_mpeg1_rl_vlc,
TEX_VLC_BITS, 2, 0);
if (level != 0) {
i += run;
if (i > MAX_INDEX)
break;
j = scantable[i];
level = (level * qscale * quant_matrix[j]) >> 4;
level = (level - 1) | 1;
level = (level ^ SHOW_SBITS(re, gb, 1)) -
SHOW_SBITS(re, gb, 1);
SKIP_BITS(re, gb, 1);
} else {
/* escape */
run = SHOW_UBITS(re, gb, 6) + 1;
LAST_SKIP_BITS(re, gb, 6);
UPDATE_CACHE(re, gb);
level = SHOW_SBITS(re, gb, 8);
SKIP_BITS(re, gb, 8);
if (level == -128) {
level = SHOW_UBITS(re, gb, 8) - 256;
SKIP_BITS(re, gb, 8);
} else if (level == 0) {
level = SHOW_UBITS(re, gb, 8);
SKIP_BITS(re, gb, 8);
}
i += run;
if (i > MAX_INDEX)
break;
j = scantable[i];
if (level < 0) {
level = -level;
level = (level * qscale * quant_matrix[j]) >> 4;
level = (level - 1) | 1;
level = -level;
} else {
level = (level * qscale * quant_matrix[j]) >> 4;
level = (level - 1) | 1;
}
}
block[j] = level;
if (((int32_t)GET_CACHE(re, gb)) <= (int32_t)0xBFFFFFFF)
break;
UPDATE_CACHE(re, gb);
}
end:
LAST_SKIP_BITS(re, gb, 2);
CLOSE_READER(re, gb);
}
if (i > MAX_INDEX)
i = AVERROR_INVALIDDATA;
return i;
}
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