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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 "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 set_dim_ret = 0;
48  int bit_rate = 0;
49  int vbv_delay = 0;
50 //FIXME replace the crap with get_bits()
51  s->repeat_pict = 0;
52 
53  while (buf < buf_end) {
54  start_code= -1;
55  buf= avpriv_find_start_code(buf, buf_end, &start_code);
56  bytes_left = buf_end - buf;
57  switch(start_code) {
58  case PICTURE_START_CODE:
59  if (bytes_left >= 2) {
60  s->pict_type = (buf[1] >> 3) & 7;
61  if (bytes_left >= 4)
62  vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
63  }
64  break;
65  case SEQ_START_CODE:
66  if (bytes_left >= 7) {
67  pc->width = (buf[0] << 4) | (buf[1] >> 4);
68  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
69  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
70  set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
71  did_set_size=1;
72  }
73  frame_rate_index = buf[3] & 0xf;
74  pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
75  bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
76  avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
77  avctx->ticks_per_frame = 1;
78  }
79  break;
80  case EXT_START_CODE:
81  if (bytes_left >= 1) {
82  ext_type = (buf[0] >> 4);
83  switch(ext_type) {
84  case 0x1: /* sequence extension */
85  if (bytes_left >= 6) {
86  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
87  vert_size_ext = (buf[2] >> 5) & 3;
88  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
89  frame_rate_ext_n = (buf[5] >> 5) & 3;
90  frame_rate_ext_d = (buf[5] & 0x1f);
91  pc->progressive_sequence = buf[1] & (1 << 3);
92  avctx->has_b_frames= !(buf[5] >> 7);
93 
94  pc->width = (pc->width & 0xFFF) | (horiz_size_ext << 12);
95  pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
96  bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
97  if(did_set_size)
98  set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
99  avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
100  avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
101  avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
102  avctx->ticks_per_frame = 2;
103  }
104  break;
105  case 0x8: /* picture coding extension */
106  if (bytes_left >= 5) {
107  top_field_first = buf[3] & (1 << 7);
108  repeat_first_field = buf[3] & (1 << 1);
109  progressive_frame = buf[4] & (1 << 7);
110 
111  /* check if we must repeat the frame */
112  s->repeat_pict = 1;
113  if (repeat_first_field) {
114  if (pc->progressive_sequence) {
115  if (top_field_first)
116  s->repeat_pict = 5;
117  else
118  s->repeat_pict = 3;
119  } else if (progressive_frame) {
120  s->repeat_pict = 2;
121  }
122  }
123 
124  if (!pc->progressive_sequence) {
125  if (top_field_first)
126  s->field_order = AV_FIELD_TT;
127  else
128  s->field_order = AV_FIELD_BB;
129  } else
130  s->field_order = AV_FIELD_PROGRESSIVE;
131  }
132  break;
133  }
134  }
135  break;
136  case -1:
137  goto the_end;
138  default:
139  /* we stop parsing when we encounter a slice. It ensures
140  that this function takes a negligible amount of time */
141  if (start_code >= SLICE_MIN_START_CODE &&
142  start_code <= SLICE_MAX_START_CODE)
143  goto the_end;
144  break;
145  }
146  }
147  the_end: ;
148  if (set_dim_ret < 0)
149  av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
150 
151  if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
152  avctx->rc_max_rate = 400*bit_rate;
153  }
154  if (bit_rate &&
155  ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
156  avctx->bit_rate = 400*bit_rate;
157  }
158 #if FF_API_AVCTX_TIMEBASE
159  if (avctx->framerate.num)
160  avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
161 #endif
162 }
163 
164 static int mpegvideo_parse(AVCodecParserContext *s,
165  AVCodecContext *avctx,
166  const uint8_t **poutbuf, int *poutbuf_size,
167  const uint8_t *buf, int buf_size)
168 {
169  struct MpvParseContext *pc1 = s->priv_data;
170  ParseContext *pc= &pc1->pc;
171  int next;
172 
173  if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
174  next= buf_size;
175  }else{
176  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
177 
178  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
179  *poutbuf = NULL;
180  *poutbuf_size = 0;
181  return buf_size;
182  }
183 
184  }
185  /* we have a full frame : we just parse the first few MPEG headers
186  to have the full timing information. The time take by this
187  function should be negligible for uncorrupted streams */
188  mpegvideo_extract_headers(s, avctx, buf, buf_size);
189  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
190  s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
191 
192  *poutbuf = buf;
193  *poutbuf_size = buf_size;
194  return next;
195 }
196 
197 static int mpegvideo_split(AVCodecContext *avctx,
198  const uint8_t *buf, int buf_size)
199 {
200  int i;
201  uint32_t state= -1;
202  int found=0;
203 
204  for(i=0; i<buf_size; i++){
205  state= (state<<8) | buf[i];
206  if(state == 0x1B3){
207  found=1;
208  }else if(found && state != 0x1B5 && state < 0x200 && state >= 0x100)
209  return i-3;
210  }
211  return 0;
212 }
213 
214 static int mpegvideo_parse_init(AVCodecParserContext *s)
215 {
216  s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
217  return 0;
218 }
219 
220 AVCodecParser ff_mpegvideo_parser = {
221  .codec_ids = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
222  .priv_data_size = sizeof(struct MpvParseContext),
223  .parser_init = mpegvideo_parse_init,
224  .parser_parse = mpegvideo_parse,
225  .parser_close = ff_parse_close,
226  .split = mpegvideo_split,
227 };
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