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 
30  int width, height;
31 };
32 
33 
35  AVCodecContext *avctx,
36  const uint8_t *buf, int buf_size)
37 {
38  struct MpvParseContext *pc = s->priv_data;
39  const uint8_t *buf_end = buf + buf_size;
40  uint32_t start_code;
41  int frame_rate_index, ext_type, bytes_left;
42  int frame_rate_ext_n, frame_rate_ext_d;
43  int top_field_first, repeat_first_field, progressive_frame;
44  int horiz_size_ext, vert_size_ext, bit_rate_ext;
45  int did_set_size=0;
46 //FIXME replace the crap with get_bits()
47  s->repeat_pict = 0;
48 
49  while (buf < buf_end) {
50  start_code= -1;
51  buf= avpriv_mpv_find_start_code(buf, buf_end, &start_code);
52  bytes_left = buf_end - buf;
53  switch(start_code) {
54  case PICTURE_START_CODE:
55  if (bytes_left >= 2) {
56  s->pict_type = (buf[1] >> 3) & 7;
57  }
58  break;
59  case SEQ_START_CODE:
60  if (bytes_left >= 7) {
61  pc->width = (buf[0] << 4) | (buf[1] >> 4);
62  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
63  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
64  avcodec_set_dimensions(avctx, pc->width, pc->height);
65  did_set_size=1;
66  }
67  frame_rate_index = buf[3] & 0xf;
68  pc->frame_rate.den = avctx->time_base.den = ff_mpeg12_frame_rate_tab[frame_rate_index].num;
69  pc->frame_rate.num = avctx->time_base.num = ff_mpeg12_frame_rate_tab[frame_rate_index].den;
70  avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
72  }
73  break;
74  case EXT_START_CODE:
75  if (bytes_left >= 1) {
76  ext_type = (buf[0] >> 4);
77  switch(ext_type) {
78  case 0x1: /* sequence extension */
79  if (bytes_left >= 6) {
80  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
81  vert_size_ext = (buf[2] >> 5) & 3;
82  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
83  frame_rate_ext_n = (buf[5] >> 5) & 3;
84  frame_rate_ext_d = (buf[5] & 0x1f);
85  pc->progressive_sequence = buf[1] & (1 << 3);
86  avctx->has_b_frames= !(buf[5] >> 7);
87 
88  pc->width |=(horiz_size_ext << 12);
89  pc->height |=( vert_size_ext << 12);
90  avctx->bit_rate += (bit_rate_ext << 18) * 400;
91  if(did_set_size)
92  avcodec_set_dimensions(avctx, pc->width, pc->height);
93  avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
94  avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
96  }
97  break;
98  case 0x8: /* picture coding extension */
99  if (bytes_left >= 5) {
100  top_field_first = buf[3] & (1 << 7);
101  repeat_first_field = buf[3] & (1 << 1);
102  progressive_frame = buf[4] & (1 << 7);
103 
104  /* check if we must repeat the frame */
105  s->repeat_pict = 1;
106  if (repeat_first_field) {
107  if (pc->progressive_sequence) {
108  if (top_field_first)
109  s->repeat_pict = 5;
110  else
111  s->repeat_pict = 3;
112  } else if (progressive_frame) {
113  s->repeat_pict = 2;
114  }
115  }
116  }
117  break;
118  }
119  }
120  break;
121  case -1:
122  goto the_end;
123  default:
124  /* we stop parsing when we encounter a slice. It ensures
125  that this function takes a negligible amount of time */
126  if (start_code >= SLICE_MIN_START_CODE &&
127  start_code <= SLICE_MAX_START_CODE)
128  goto the_end;
129  break;
130  }
131  }
132  the_end: ;
133 }
134 
136  AVCodecContext *avctx,
137  const uint8_t **poutbuf, int *poutbuf_size,
138  const uint8_t *buf, int buf_size)
139 {
140  struct MpvParseContext *pc1 = s->priv_data;
141  ParseContext *pc= &pc1->pc;
142  int next;
143 
145  next= buf_size;
146  }else{
147  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
148 
149  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
150  *poutbuf = NULL;
151  *poutbuf_size = 0;
152  return buf_size;
153  }
154 
155  }
156  /* we have a full frame : we just parse the first few MPEG headers
157  to have the full timing information. The time take by this
158  function should be negligible for uncorrupted streams */
159  mpegvideo_extract_headers(s, avctx, buf, buf_size);
160  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
161  s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
162 
163  *poutbuf = buf;
164  *poutbuf_size = buf_size;
165  return next;
166 }
167 
168 static int mpegvideo_split(AVCodecContext *avctx,
169  const uint8_t *buf, int buf_size)
170 {
171  int i;
172  uint32_t state= -1;
173 
174  for(i=0; i<buf_size; i++){
175  state= (state<<8) | buf[i];
176  if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
177  return i-3;
178  }
179  return 0;
180 }
181 
184  .priv_data_size = sizeof(struct MpvParseContext),
185  .parser_parse = mpegvideo_parse,
186  .parser_close = ff_parse_close,
187  .split = mpegvideo_split,
188 };