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 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 
91  bit_rate_ext <<= 18;
92  if (bit_rate_ext < INT_MAX / 400 &&
93  bit_rate_ext * 400 < INT_MAX - avctx->bit_rate) {
94  avctx->bit_rate += bit_rate_ext * 400;
95  } else
96  avctx->bit_rate = 0;
97 
98  if(did_set_size)
99  avcodec_set_dimensions(avctx, pc->width, pc->height);
100  avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
101  avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
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  break;
125  }
126  }
127  break;
128  case -1:
129  goto the_end;
130  default:
131  /* we stop parsing when we encounter a slice. It ensures
132  that this function takes a negligible amount of time */
133  if (start_code >= SLICE_MIN_START_CODE &&
134  start_code <= SLICE_MAX_START_CODE)
135  goto the_end;
136  break;
137  }
138  }
139  the_end: ;
140 }
141 
143  AVCodecContext *avctx,
144  const uint8_t **poutbuf, int *poutbuf_size,
145  const uint8_t *buf, int buf_size)
146 {
147  struct MpvParseContext *pc1 = s->priv_data;
148  ParseContext *pc= &pc1->pc;
149  int next;
150 
152  next= buf_size;
153  }else{
154  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
155 
156  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
157  *poutbuf = NULL;
158  *poutbuf_size = 0;
159  return buf_size;
160  }
161 
162  }
163  /* we have a full frame : we just parse the first few MPEG headers
164  to have the full timing information. The time take by this
165  function should be negligible for uncorrupted streams */
166  mpegvideo_extract_headers(s, avctx, buf, buf_size);
167  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
168  s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
169 
170  *poutbuf = buf;
171  *poutbuf_size = buf_size;
172  return next;
173 }
174 
175 static int mpegvideo_split(AVCodecContext *avctx,
176  const uint8_t *buf, int buf_size)
177 {
178  int i;
179  uint32_t state= -1;
180 
181  for(i=0; i<buf_size; i++){
182  state= (state<<8) | buf[i];
183  if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
184  return i-3;
185  }
186  return 0;
187 }
188 
191  .priv_data_size = sizeof(struct MpvParseContext),
192  .parser_parse = mpegvideo_parse,
193  .parser_close = ff_parse_close,
194  .split = mpegvideo_split,
195 };
#define SLICE_MAX_START_CODE
Definition: cavs.h:30
static int mpegvideo_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
int coded_width
Bitstream width / height, may be different from width/height.
Definition: avcodec.h:1515
int num
numerator
Definition: rational.h:44
void avcodec_set_dimensions(AVCodecContext *s, int width, int height)
Definition: utils.c:149
int codec_ids[5]
Definition: avcodec.h:3855
mpegvideo header.
av_dlog(ac->avr,"%d samples - audio_convert: %s to %s (%s)\n", len, av_get_sample_fmt_name(ac->in_fmt), av_get_sample_fmt_name(ac->out_fmt), use_generic?ac->func_descr_generic:ac->func_descr)
#define SLICE_MIN_START_CODE
Definition: mpegvideo.h:79
ParseContext pc
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avcodec.h:1465
uint8_t
int has_b_frames
Size of the frame reordering buffer in the decoder.
Definition: avcodec.h:1634
int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_size)
Combine the (truncated) bitstream to a complete frame.
Definition: parser.c:215
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:280
int bit_rate
the average bitrate
Definition: avcodec.h:1404
int width
picture width / height.
Definition: avcodec.h:1508
#define EXT_START_CODE
Definition: cavs.h:31
preferred ID for MPEG-1/2 video decoding
Definition: avcodec.h:100
NULL
Definition: eval.c:52
AVRational frame_rate
const uint8_t * avpriv_mpv_find_start_code(const uint8_t *restrict p, const uint8_t *end, uint32_t *restrict state)
Definition: mpegvideo.c:174
enum AVCodecID codec_id
Definition: avcodec.h:1350
main external API structure.
Definition: avcodec.h:1339
int coded_height
Definition: avcodec.h:1515
rational number numerator/denominator
Definition: rational.h:43
int ff_mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size, AVCodecParserContext *s)
Find the end of the current frame in the bitstream.
Definition: mpeg12.c:2150
AVCodecParser ff_mpegvideo_parser
static uint32_t state
Definition: trasher.c:27
static void mpegvideo_extract_headers(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
static int mpegvideo_split(AVCodecContext *avctx, const uint8_t *buf, int buf_size)
int den
denominator
Definition: rational.h:45
#define SEQ_START_CODE
Definition: mpegvideo.h:76
int repeat_pict
This field is used for proper frame duration computation in lavf.
Definition: avcodec.h:3737
#define PICTURE_START_CODE
Definition: mpegvideo.h:78
const AVRational ff_mpeg12_frame_rate_tab[16]
Definition: mpeg12data.c:308