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FFmpeg/libavcodec/mpeg12.c
Andreas Rheinhardt 2d764069be avcodec/vlc: Use structure instead of VLC_TYPE array as VLC element 
In C, qualifiers for arrays are broken:
const VLC_TYPE (*foo)[2] is a pointer to an array of two const VLC_TYPE
elements and unfortunately this is not compatible with a pointer
to a const array of two VLC_TYPE, because the latter does not exist
as array types are never qualified (the qualifier applies to the base
type instead). This is the reason why get_vlc2() doesn't accept
a const VLC table despite not modifying the table at all, as
there is no automatic conversion from VLC_TYPE (*)[2] to
const VLC_TYPE (*)[2].

Fix this by using a structure VLCElem for the VLC table.
This also has the advantage of making it clear which
element is which.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-06-17 16:47:29 +02:00

329 lines
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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 "mpeg12data.h"
#include "mpeg12dec.h"
#include "mpegvideodata.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(RLTable *rl, 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));
init_vlc(&vlc, TEX_VLC_BITS, rl->n + 2, &rl->table_vlc[0][1], 4, 2, &rl->table_vlc[0][0], 4, 2, INIT_VLC_USE_NEW_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 == rl->n) { //esc
run = 65;
level = 0;
} else if (code == rl->n+1) { //eob
run = 0;
level = 127;
} else {
run = rl->table_run [code] + 1;
level = rl->table_level[code];
}
}
rl->rl_vlc[0][i].len = len;
rl->rl_vlc[0][i].level = level;
rl->rl_vlc[0][i].run = run;
}
}
av_cold void ff_mpeg12_common_init(MpegEncContext *s)
{
s->y_dc_scale_table =
s->c_dc_scale_table = ff_mpeg2_dc_scale_table[s->intra_dc_precision];
}
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 */
VLC ff_mv_vlc;
VLC ff_dc_lum_vlc;
VLC ff_dc_chroma_vlc;
VLC ff_mbincr_vlc;
VLC ff_mb_ptype_vlc;
VLC ff_mb_btype_vlc;
VLC ff_mb_pat_vlc;
static av_cold void mpeg12_init_vlcs(void)
{
INIT_VLC_STATIC(&ff_dc_lum_vlc, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_lum_bits, 1, 1,
ff_mpeg12_vlc_dc_lum_code, 2, 2, 512);
INIT_VLC_STATIC(&ff_dc_chroma_vlc, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_chroma_bits, 1, 1,
ff_mpeg12_vlc_dc_chroma_code, 2, 2, 514);
INIT_VLC_STATIC(&ff_mv_vlc, MV_VLC_BITS, 17,
&ff_mpeg12_mbMotionVectorTable[0][1], 2, 1,
&ff_mpeg12_mbMotionVectorTable[0][0], 2, 1, 266);
INIT_VLC_STATIC(&ff_mbincr_vlc, MBINCR_VLC_BITS, 36,
&ff_mpeg12_mbAddrIncrTable[0][1], 2, 1,
&ff_mpeg12_mbAddrIncrTable[0][0], 2, 1, 538);
INIT_VLC_STATIC(&ff_mb_pat_vlc, MB_PAT_VLC_BITS, 64,
&ff_mpeg12_mbPatTable[0][1], 2, 1,
&ff_mpeg12_mbPatTable[0][0], 2, 1, 512);
INIT_VLC_STATIC(&ff_mb_ptype_vlc, MB_PTYPE_VLC_BITS, 7,
&table_mb_ptype[0][1], 2, 1,
&table_mb_ptype[0][0], 2, 1, 64);
INIT_VLC_STATIC(&ff_mb_btype_vlc, MB_BTYPE_VLC_BITS, 11,
&table_mb_btype[0][1], 2, 1,
&table_mb_btype[0][0], 2, 1, 64);
INIT_2D_VLC_RL(ff_rl_mpeg1, 680, 0);
INIT_2D_VLC_RL(ff_rl_mpeg2, 674, 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);
}
#if FF_API_FLAG_TRUNCATED
/**
* Find the end of the current frame in the bitstream.
* @return the position of the first byte of the next frame, or -1
*/
int ff_mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size, AVCodecParserContext *s)
{
int i;
uint32_t state = pc->state;
/* EOF considered as end of frame */
if (buf_size == 0)
return 0;
/*
0 frame start -> 1/4
1 first_SEQEXT -> 0/2
2 first field start -> 3/0
3 second_SEQEXT -> 2/0
4 searching end
*/
for (i = 0; i < buf_size; i++) {
av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
if (pc->frame_start_found & 1) {
if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
pc->frame_start_found--;
else if (state == EXT_START_CODE + 2) {
if ((buf[i] & 3) == 3)
pc->frame_start_found = 0;
else
pc->frame_start_found = (pc->frame_start_found + 1) & 3;
}
state++;
} else {
i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {
i++;
pc->frame_start_found = 4;
}
if (state == SEQ_END_CODE) {
pc->frame_start_found = 0;
pc->state=-1;
return i+1;
}
if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
pc->frame_start_found = 0;
if (pc->frame_start_found < 4 && state == EXT_START_CODE)
pc->frame_start_found++;
if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
pc->frame_start_found = 0;
pc->state = -1;
return i - 3;
}
}
if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
ff_fetch_timestamp(s, i - 3, 1, i > 3);
}
}
}
pc->state = state;
return END_NOT_FOUND;
}
#endif
#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;
RLTable *rl = &ff_rl_mpeg1;
/* 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, rl->rl_vlc[0],
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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