mpegvideo_parser.c
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1 /*
2  * MPEG1 / MPEG2 video parser
3  * Copyright (c) 2000,2001 Fabrice Bellard
4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5  *
6  * This file is part of Libav.
7  *
8  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #include "parser.h"
24 #include "mpegvideo.h"
25 
28  const uint8_t *buf, int buf_size)
29 {
30  ParseContext1 *pc = s->priv_data;
31  const uint8_t *buf_end = buf + buf_size;
32  uint32_t start_code;
33  int frame_rate_index, ext_type, bytes_left;
34  int frame_rate_ext_n, frame_rate_ext_d;
36  int horiz_size_ext, vert_size_ext, bit_rate_ext;
37  int did_set_size=0;
38 //FIXME replace the crap with get_bits()
39  s->repeat_pict = 0;
40 
41  while (buf < buf_end) {
42  start_code= -1;
43  buf= avpriv_mpv_find_start_code(buf, buf_end, &start_code);
44  bytes_left = buf_end - buf;
45  switch(start_code) {
46  case PICTURE_START_CODE:
47  if (bytes_left >= 2) {
48  s->pict_type = (buf[1] >> 3) & 7;
49  }
50  break;
51  case SEQ_START_CODE:
52  if (bytes_left >= 7) {
53  pc->width = (buf[0] << 4) | (buf[1] >> 4);
54  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
55  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
56  avcodec_set_dimensions(avctx, pc->width, pc->height);
57  did_set_size=1;
58  }
59  frame_rate_index = buf[3] & 0xf;
62  avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
64  avctx->sub_id = 1;
65  }
66  break;
67  case EXT_START_CODE:
68  if (bytes_left >= 1) {
69  ext_type = (buf[0] >> 4);
70  switch(ext_type) {
71  case 0x1: /* sequence extension */
72  if (bytes_left >= 6) {
73  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
74  vert_size_ext = (buf[2] >> 5) & 3;
75  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
76  frame_rate_ext_n = (buf[5] >> 5) & 3;
77  frame_rate_ext_d = (buf[5] & 0x1f);
78  pc->progressive_sequence = buf[1] & (1 << 3);
79  avctx->has_b_frames= !(buf[5] >> 7);
80 
81  pc->width |=(horiz_size_ext << 12);
82  pc->height |=( vert_size_ext << 12);
83  avctx->bit_rate += (bit_rate_ext << 18) * 400;
84  if(did_set_size)
85  avcodec_set_dimensions(avctx, pc->width, pc->height);
86  avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
87  avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
89  avctx->sub_id = 2; /* forces MPEG2 */
90  }
91  break;
92  case 0x8: /* picture coding extension */
93  if (bytes_left >= 5) {
94  top_field_first = buf[3] & (1 << 7);
95  repeat_first_field = buf[3] & (1 << 1);
96  progressive_frame = buf[4] & (1 << 7);
97 
98  /* check if we must repeat the frame */
99  s->repeat_pict = 1;
100  if (repeat_first_field) {
101  if (pc->progressive_sequence) {
102  if (top_field_first)
103  s->repeat_pict = 5;
104  else
105  s->repeat_pict = 3;
106  } else if (progressive_frame) {
107  s->repeat_pict = 2;
108  }
109  }
110  }
111  break;
112  }
113  }
114  break;
115  case -1:
116  goto the_end;
117  default:
118  /* we stop parsing when we encounter a slice. It ensures
119  that this function takes a negligible amount of time */
120  if (start_code >= SLICE_MIN_START_CODE &&
121  start_code <= SLICE_MAX_START_CODE)
122  goto the_end;
123  break;
124  }
125  }
126  the_end: ;
127 }
128 
131  const uint8_t **poutbuf, int *poutbuf_size,
132  const uint8_t *buf, int buf_size)
133 {
134  ParseContext1 *pc1 = s->priv_data;
135  ParseContext *pc= &pc1->pc;
136  int next;
137 
139  next= buf_size;
140  }else{
141  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
142 
143  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
144  *poutbuf = NULL;
145  *poutbuf_size = 0;
146  return buf_size;
147  }
148 
149  }
150  /* we have a full frame : we just parse the first few MPEG headers
151  to have the full timing information. The time take by this
152  function should be negligible for uncorrupted streams */
153  mpegvideo_extract_headers(s, avctx, buf, buf_size);
154  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
155  s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
156 
157  *poutbuf = buf;
158  *poutbuf_size = buf_size;
159  return next;
160 }
161 
163  const uint8_t *buf, int buf_size)
164 {
165  int i;
166  uint32_t state= -1;
167 
168  for(i=0; i<buf_size; i++){
169  state= (state<<8) | buf[i];
170  if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
171  return i-3;
172  }
173  return 0;
174 }
175 
178  .priv_data_size = sizeof(ParseContext1),
179  .parser_parse = mpegvideo_parse,
180  .parser_close = ff_parse1_close,
181  .split = mpegvideo_split,
182 };