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mpeg12.c
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1 /*
2  * MPEG-1/2 decoder
3  * Copyright (c) 2000, 2001 Fabrice Bellard
4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  * MPEG-1/2 decoder
26  */
27 
28 #define UNCHECKED_BITSTREAM_READER 1
29 
30 #include "libavutil/attributes.h"
31 #include "libavutil/avassert.h"
32 #include "libavutil/timecode.h"
33 
34 #include "internal.h"
35 #include "avcodec.h"
36 #include "mpegvideo.h"
37 #include "error_resilience.h"
38 #include "mpeg12.h"
39 #include "mpeg12data.h"
40 #include "bytestream.h"
41 #include "vdpau_internal.h"
42 #include "thread.h"
43 
44 uint8_t ff_mpeg12_static_rl_table_store[2][2][2*MAX_RUN + MAX_LEVEL + 3];
45 
46 static const uint8_t table_mb_ptype[7][2] = {
47  { 3, 5 }, // 0x01 MB_INTRA
48  { 1, 2 }, // 0x02 MB_PAT
49  { 1, 3 }, // 0x08 MB_FOR
50  { 1, 1 }, // 0x0A MB_FOR|MB_PAT
51  { 1, 6 }, // 0x11 MB_QUANT|MB_INTRA
52  { 1, 5 }, // 0x12 MB_QUANT|MB_PAT
53  { 2, 5 }, // 0x1A MB_QUANT|MB_FOR|MB_PAT
54 };
55 
56 static const uint8_t table_mb_btype[11][2] = {
57  { 3, 5 }, // 0x01 MB_INTRA
58  { 2, 3 }, // 0x04 MB_BACK
59  { 3, 3 }, // 0x06 MB_BACK|MB_PAT
60  { 2, 4 }, // 0x08 MB_FOR
61  { 3, 4 }, // 0x0A MB_FOR|MB_PAT
62  { 2, 2 }, // 0x0C MB_FOR|MB_BACK
63  { 3, 2 }, // 0x0E MB_FOR|MB_BACK|MB_PAT
64  { 1, 6 }, // 0x11 MB_QUANT|MB_INTRA
65  { 2, 6 }, // 0x16 MB_QUANT|MB_BACK|MB_PAT
66  { 3, 6 }, // 0x1A MB_QUANT|MB_FOR|MB_PAT
67  { 2, 5 }, // 0x1E MB_QUANT|MB_FOR|MB_BACK|MB_PAT
68 };
69 
70 #define INIT_2D_VLC_RL(rl, static_size)\
71 {\
72  static RL_VLC_ELEM rl_vlc_table[static_size];\
73  rl.rl_vlc[0] = rl_vlc_table;\
74  init_2d_vlc_rl(&rl, static_size);\
75 }
76 
77 static av_cold void init_2d_vlc_rl(RLTable *rl, unsigned static_size)
78 {
79  int i;
80  VLC_TYPE table[680][2] = {{0}};
81  VLC vlc = { .table = table, .table_allocated = static_size };
82  av_assert0(static_size <= FF_ARRAY_ELEMS(table));
83  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);
84 
85  for (i = 0; i < vlc.table_size; i++) {
86  int code = vlc.table[i][0];
87  int len = vlc.table[i][1];
88  int level, run;
89 
90  if (len == 0) { // illegal code
91  run = 65;
92  level = MAX_LEVEL;
93  } else if (len<0) { //more bits needed
94  run = 0;
95  level = code;
96  } else {
97  if (code == rl->n) { //esc
98  run = 65;
99  level = 0;
100  } else if (code == rl->n+1) { //eob
101  run = 0;
102  level = 127;
103  } else {
104  run = rl->table_run [code] + 1;
105  level = rl->table_level[code];
106  }
107  }
108  rl->rl_vlc[0][i].len = len;
109  rl->rl_vlc[0][i].level = level;
110  rl->rl_vlc[0][i].run = run;
111  }
112 }
113 
114 av_cold void ff_mpeg12_common_init(MpegEncContext *s)
115 {
116 
117  s->y_dc_scale_table =
118  s->c_dc_scale_table = ff_mpeg2_dc_scale_table[s->intra_dc_precision];
119 
120 }
121 
122 void ff_mpeg1_clean_buffers(MpegEncContext *s)
123 {
124  s->last_dc[0] = 1 << (7 + s->intra_dc_precision);
125  s->last_dc[1] = s->last_dc[0];
126  s->last_dc[2] = s->last_dc[0];
127  memset(s->last_mv, 0, sizeof(s->last_mv));
128 }
129 
130 
131 /******************************************/
132 /* decoding */
133 
134 VLC ff_mv_vlc;
135 
136 VLC ff_dc_lum_vlc;
137 VLC ff_dc_chroma_vlc;
138 
139 VLC ff_mbincr_vlc;
140 VLC ff_mb_ptype_vlc;
141 VLC ff_mb_btype_vlc;
142 VLC ff_mb_pat_vlc;
143 
144 av_cold void ff_mpeg12_init_vlcs(void)
145 {
146  static int done = 0;
147 
148  if (!done) {
149  done = 1;
150 
151  INIT_VLC_STATIC(&ff_dc_lum_vlc, DC_VLC_BITS, 12,
152  ff_mpeg12_vlc_dc_lum_bits, 1, 1,
153  ff_mpeg12_vlc_dc_lum_code, 2, 2, 512);
154  INIT_VLC_STATIC(&ff_dc_chroma_vlc, DC_VLC_BITS, 12,
155  ff_mpeg12_vlc_dc_chroma_bits, 1, 1,
156  ff_mpeg12_vlc_dc_chroma_code, 2, 2, 514);
157  INIT_VLC_STATIC(&ff_mv_vlc, MV_VLC_BITS, 17,
158  &ff_mpeg12_mbMotionVectorTable[0][1], 2, 1,
159  &ff_mpeg12_mbMotionVectorTable[0][0], 2, 1, 518);
160  INIT_VLC_STATIC(&ff_mbincr_vlc, MBINCR_VLC_BITS, 36,
161  &ff_mpeg12_mbAddrIncrTable[0][1], 2, 1,
162  &ff_mpeg12_mbAddrIncrTable[0][0], 2, 1, 538);
163  INIT_VLC_STATIC(&ff_mb_pat_vlc, MB_PAT_VLC_BITS, 64,
164  &ff_mpeg12_mbPatTable[0][1], 2, 1,
165  &ff_mpeg12_mbPatTable[0][0], 2, 1, 512);
166 
167  INIT_VLC_STATIC(&ff_mb_ptype_vlc, MB_PTYPE_VLC_BITS, 7,
168  &table_mb_ptype[0][1], 2, 1,
169  &table_mb_ptype[0][0], 2, 1, 64);
170  INIT_VLC_STATIC(&ff_mb_btype_vlc, MB_BTYPE_VLC_BITS, 11,
171  &table_mb_btype[0][1], 2, 1,
172  &table_mb_btype[0][0], 2, 1, 64);
173  ff_init_rl(&ff_rl_mpeg1, ff_mpeg12_static_rl_table_store[0]);
174  ff_init_rl(&ff_rl_mpeg2, ff_mpeg12_static_rl_table_store[1]);
175 
176  INIT_2D_VLC_RL(ff_rl_mpeg1, 680);
177  INIT_2D_VLC_RL(ff_rl_mpeg2, 674);
178  }
179 }
180 
181 /**
182  * Find the end of the current frame in the bitstream.
183  * @return the position of the first byte of the next frame, or -1
184  */
185 int ff_mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size, AVCodecParserContext *s)
186 {
187  int i;
188  uint32_t state = pc->state;
189 
190  /* EOF considered as end of frame */
191  if (buf_size == 0)
192  return 0;
193 
194 /*
195  0 frame start -> 1/4
196  1 first_SEQEXT -> 0/2
197  2 first field start -> 3/0
198  3 second_SEQEXT -> 2/0
199  4 searching end
200 */
201 
202  for (i = 0; i < buf_size; i++) {
203  av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
204  if (pc->frame_start_found & 1) {
205  if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
206  pc->frame_start_found--;
207  else if (state == EXT_START_CODE + 2) {
208  if ((buf[i] & 3) == 3)
209  pc->frame_start_found = 0;
210  else
211  pc->frame_start_found = (pc->frame_start_found + 1) & 3;
212  }
213  state++;
214  } else {
215  i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
216  if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {
217  i++;
218  pc->frame_start_found = 4;
219  }
220  if (state == SEQ_END_CODE) {
221  pc->frame_start_found = 0;
222  pc->state=-1;
223  return i+1;
224  }
225  if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
226  pc->frame_start_found = 0;
227  if (pc->frame_start_found < 4 && state == EXT_START_CODE)
228  pc->frame_start_found++;
229  if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
230  if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
231  pc->frame_start_found = 0;
232  pc->state = -1;
233  return i - 3;
234  }
235  }
236  if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
237  ff_fetch_timestamp(s, i - 3, 1);
238  }
239  }
240  }
241  pc->state = state;
242  return END_NOT_FOUND;
243 }
244 
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