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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 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 #include "parser.h"
24 #include "mpegvideo.h"
25 
26 struct MpvParseContext {
27  ParseContext pc;
28  AVRational frame_rate;
29  int progressive_sequence;
30  int width, height;
31 };
32 
33 
34 static void mpegvideo_extract_headers(AVCodecParserContext *s,
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  int bit_rate = 0;
47  int vbv_delay = 0;
48 //FIXME replace the crap with get_bits()
49  s->repeat_pict = 0;
50 
51  while (buf < buf_end) {
52  start_code= -1;
53  buf= avpriv_mpv_find_start_code(buf, buf_end, &start_code);
54  bytes_left = buf_end - buf;
55  switch(start_code) {
56  case PICTURE_START_CODE:
57  if (bytes_left >= 2) {
58  s->pict_type = (buf[1] >> 3) & 7;
59  if (bytes_left >= 4)
60  vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
61  }
62  break;
63  case SEQ_START_CODE:
64  if (bytes_left >= 7) {
65  pc->width = (buf[0] << 4) | (buf[1] >> 4);
66  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
67  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
68  avcodec_set_dimensions(avctx, pc->width, pc->height);
69  did_set_size=1;
70  }
71  frame_rate_index = buf[3] & 0xf;
72  pc->frame_rate.den = avctx->time_base.den = ff_mpeg12_frame_rate_tab[frame_rate_index].num;
73  pc->frame_rate.num = avctx->time_base.num = ff_mpeg12_frame_rate_tab[frame_rate_index].den;
74  bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
75  avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
76  }
77  break;
78  case EXT_START_CODE:
79  if (bytes_left >= 1) {
80  ext_type = (buf[0] >> 4);
81  switch(ext_type) {
82  case 0x1: /* sequence extension */
83  if (bytes_left >= 6) {
84  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
85  vert_size_ext = (buf[2] >> 5) & 3;
86  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
87  frame_rate_ext_n = (buf[5] >> 5) & 3;
88  frame_rate_ext_d = (buf[5] & 0x1f);
89  pc->progressive_sequence = buf[1] & (1 << 3);
90  avctx->has_b_frames= !(buf[5] >> 7);
91 
92  pc->width |=(horiz_size_ext << 12);
93  pc->height |=( vert_size_ext << 12);
94  bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
95  if(did_set_size)
96  avcodec_set_dimensions(avctx, pc->width, pc->height);
97  avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
98  avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
99  avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
100  }
101  break;
102  case 0x8: /* picture coding extension */
103  if (bytes_left >= 5) {
104  top_field_first = buf[3] & (1 << 7);
105  repeat_first_field = buf[3] & (1 << 1);
106  progressive_frame = buf[4] & (1 << 7);
107 
108  /* check if we must repeat the frame */
109  s->repeat_pict = 1;
110  if (repeat_first_field) {
111  if (pc->progressive_sequence) {
112  if (top_field_first)
113  s->repeat_pict = 5;
114  else
115  s->repeat_pict = 3;
116  } else if (progressive_frame) {
117  s->repeat_pict = 2;
118  }
119  }
120  }
121  break;
122  }
123  }
124  break;
125  case -1:
126  goto the_end;
127  default:
128  /* we stop parsing when we encounter a slice. It ensures
129  that this function takes a negligible amount of time */
130  if (start_code >= SLICE_MIN_START_CODE &&
131  start_code <= SLICE_MAX_START_CODE)
132  goto the_end;
133  break;
134  }
135  }
136  the_end: ;
137  if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
138  avctx->rc_max_rate = 400*bit_rate;
139  } else if (avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate &&
140  (bit_rate != 0x3FFFF || vbv_delay != 0xFFFF)) {
141  avctx->bit_rate = 400*bit_rate;
142  }
143 }
144 
145 static int mpegvideo_parse(AVCodecParserContext *s,
146  AVCodecContext *avctx,
147  const uint8_t **poutbuf, int *poutbuf_size,
148  const uint8_t *buf, int buf_size)
149 {
150  struct MpvParseContext *pc1 = s->priv_data;
151  ParseContext *pc= &pc1->pc;
152  int next;
153 
154  if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
155  next= buf_size;
156  }else{
157  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
158 
159  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
160  *poutbuf = NULL;
161  *poutbuf_size = 0;
162  return buf_size;
163  }
164 
165  }
166  /* we have a full frame : we just parse the first few MPEG headers
167  to have the full timing information. The time take by this
168  function should be negligible for uncorrupted streams */
169  mpegvideo_extract_headers(s, avctx, buf, buf_size);
170  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
171  s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
172 
173  *poutbuf = buf;
174  *poutbuf_size = buf_size;
175  return next;
176 }
177 
178 static int mpegvideo_split(AVCodecContext *avctx,
179  const uint8_t *buf, int buf_size)
180 {
181  int i;
182  uint32_t state= -1;
183  int found=0;
184 
185  for(i=0; i<buf_size; i++){
186  state= (state<<8) | buf[i];
187  if(state == 0x1B3){
188  found=1;
189  }else if(found && state != 0x1B5 && state < 0x200 && state >= 0x100)
190  return i-3;
191  }
192  return 0;
193 }
194 
195 static int mpegvideo_parse_init(AVCodecParserContext *s)
196 {
197  s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
198  return 0;
199 }
200 
201 AVCodecParser ff_mpegvideo_parser = {
202  .codec_ids = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
203  .priv_data_size = sizeof(struct MpvParseContext),
204  .parser_init = mpegvideo_parse_init,
205  .parser_parse = mpegvideo_parse,
206  .parser_close = ff_parse_close,
207  .split = mpegvideo_split,
208 };
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