FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
mpegvideo_parser.c
Go to the documentation of this file.
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 "mpeg12.h"
25 #include "internal.h"
26 
27 struct MpvParseContext {
28  ParseContext pc;
29  AVRational frame_rate;
30  int progressive_sequence;
31  int width, height;
32 };
33 
34 
35 static void mpegvideo_extract_headers(AVCodecParserContext *s,
36  AVCodecContext *avctx,
37  const uint8_t *buf, int buf_size)
38 {
39  struct MpvParseContext *pc = s->priv_data;
40  const uint8_t *buf_end = buf + buf_size;
41  uint32_t start_code;
42  int frame_rate_index, ext_type, bytes_left;
43  int frame_rate_ext_n, frame_rate_ext_d;
44  int top_field_first, repeat_first_field, progressive_frame;
45  int horiz_size_ext, vert_size_ext, bit_rate_ext;
46  int did_set_size=0;
47  int bit_rate = 0;
48  int vbv_delay = 0;
49 //FIXME replace the crap with get_bits()
50  s->repeat_pict = 0;
51 
52  while (buf < buf_end) {
53  start_code= -1;
54  buf= avpriv_find_start_code(buf, buf_end, &start_code);
55  bytes_left = buf_end - buf;
56  switch(start_code) {
57  case PICTURE_START_CODE:
58  if (bytes_left >= 2) {
59  s->pict_type = (buf[1] >> 3) & 7;
60  if (bytes_left >= 4)
61  vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
62  }
63  break;
64  case SEQ_START_CODE:
65  if (bytes_left >= 7) {
66  pc->width = (buf[0] << 4) | (buf[1] >> 4);
67  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
68  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
69  ff_set_dimensions(avctx, pc->width, pc->height);
70  did_set_size=1;
71  }
72  frame_rate_index = buf[3] & 0xf;
73  pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
74  bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
75  avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
76  avctx->ticks_per_frame = 1;
77  }
78  break;
79  case EXT_START_CODE:
80  if (bytes_left >= 1) {
81  ext_type = (buf[0] >> 4);
82  switch(ext_type) {
83  case 0x1: /* sequence extension */
84  if (bytes_left >= 6) {
85  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
86  vert_size_ext = (buf[2] >> 5) & 3;
87  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
88  frame_rate_ext_n = (buf[5] >> 5) & 3;
89  frame_rate_ext_d = (buf[5] & 0x1f);
90  pc->progressive_sequence = buf[1] & (1 << 3);
91  avctx->has_b_frames= !(buf[5] >> 7);
92 
93  pc->width |=(horiz_size_ext << 12);
94  pc->height |=( vert_size_ext << 12);
95  bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
96  if(did_set_size)
97  ff_set_dimensions(avctx, pc->width, pc->height);
98  avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
99  avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
100  avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
101  avctx->ticks_per_frame = 2;
102  }
103  break;
104  case 0x8: /* picture coding extension */
105  if (bytes_left >= 5) {
106  top_field_first = buf[3] & (1 << 7);
107  repeat_first_field = buf[3] & (1 << 1);
108  progressive_frame = buf[4] & (1 << 7);
109 
110  /* check if we must repeat the frame */
111  s->repeat_pict = 1;
112  if (repeat_first_field) {
113  if (pc->progressive_sequence) {
114  if (top_field_first)
115  s->repeat_pict = 5;
116  else
117  s->repeat_pict = 3;
118  } else if (progressive_frame) {
119  s->repeat_pict = 2;
120  }
121  }
122 
123  if (!pc->progressive_sequence) {
124  if (top_field_first)
125  s->field_order = AV_FIELD_TT;
126  else
127  s->field_order = AV_FIELD_BB;
128  } else
129  s->field_order = AV_FIELD_PROGRESSIVE;
130  }
131  break;
132  }
133  }
134  break;
135  case -1:
136  goto the_end;
137  default:
138  /* we stop parsing when we encounter a slice. It ensures
139  that this function takes a negligible amount of time */
140  if (start_code >= SLICE_MIN_START_CODE &&
141  start_code <= SLICE_MAX_START_CODE)
142  goto the_end;
143  break;
144  }
145  }
146  the_end: ;
147  if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
148  avctx->rc_max_rate = 400*bit_rate;
149  }
150  if (bit_rate &&
151  ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
152  avctx->bit_rate = 400*bit_rate;
153  }
154 #if FF_API_AVCTX_TIMEBASE
155  if (avctx->framerate.num)
156  avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
157 #endif
158 }
159 
160 static int mpegvideo_parse(AVCodecParserContext *s,
161  AVCodecContext *avctx,
162  const uint8_t **poutbuf, int *poutbuf_size,
163  const uint8_t *buf, int buf_size)
164 {
165  struct MpvParseContext *pc1 = s->priv_data;
166  ParseContext *pc= &pc1->pc;
167  int next;
168 
169  if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
170  next= buf_size;
171  }else{
172  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
173 
174  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
175  *poutbuf = NULL;
176  *poutbuf_size = 0;
177  return buf_size;
178  }
179 
180  }
181  /* we have a full frame : we just parse the first few MPEG headers
182  to have the full timing information. The time take by this
183  function should be negligible for uncorrupted streams */
184  mpegvideo_extract_headers(s, avctx, buf, buf_size);
185  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
186  s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
187 
188  *poutbuf = buf;
189  *poutbuf_size = buf_size;
190  return next;
191 }
192 
193 static int mpegvideo_split(AVCodecContext *avctx,
194  const uint8_t *buf, int buf_size)
195 {
196  int i;
197  uint32_t state= -1;
198  int found=0;
199 
200  for(i=0; i<buf_size; i++){
201  state= (state<<8) | buf[i];
202  if(state == 0x1B3){
203  found=1;
204  }else if(found && state != 0x1B5 && state < 0x200 && state >= 0x100)
205  return i-3;
206  }
207  return 0;
208 }
209 
210 static int mpegvideo_parse_init(AVCodecParserContext *s)
211 {
212  s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
213  return 0;
214 }
215 
216 AVCodecParser ff_mpegvideo_parser = {
217  .codec_ids = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
218  .priv_data_size = sizeof(struct MpvParseContext),
219  .parser_init = mpegvideo_parse_init,
220  .parser_parse = mpegvideo_parse,
221  .parser_close = ff_parse_close,
222  .split = mpegvideo_split,
223 };
Generated on Fri Dec 5 2014 04:41:59 for FFmpeg by   doxygen 1.8.2