Libav
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 "mpeg12.h"
25 #include "internal.h"
26 
31  int width, height;
32 };
33 
34 
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 //FIXME replace the crap with get_bits()
48  s->repeat_pict = 0;
49 
50  while (buf < buf_end) {
51  start_code= -1;
52  buf= avpriv_find_start_code(buf, buf_end, &start_code);
53  bytes_left = buf_end - buf;
54  switch(start_code) {
55  case PICTURE_START_CODE:
56  if (bytes_left >= 2) {
57  s->pict_type = (buf[1] >> 3) & 7;
58  }
59  break;
60  case SEQ_START_CODE:
61  if (bytes_left >= 7) {
62  pc->width = (buf[0] << 4) | (buf[1] >> 4);
63  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
64  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
65  ff_set_dimensions(avctx, pc->width, pc->height);
66  did_set_size=1;
67  }
68  frame_rate_index = buf[3] & 0xf;
69  pc->frame_rate.den = avctx->time_base.den = ff_mpeg12_frame_rate_tab[frame_rate_index].num;
70  pc->frame_rate.num = avctx->time_base.num = ff_mpeg12_frame_rate_tab[frame_rate_index].den;
71  avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
73  }
74  break;
75  case EXT_START_CODE:
76  if (bytes_left >= 1) {
77  ext_type = (buf[0] >> 4);
78  switch(ext_type) {
79  case 0x1: /* sequence extension */
80  if (bytes_left >= 6) {
81  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
82  vert_size_ext = (buf[2] >> 5) & 3;
83  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
84  frame_rate_ext_n = (buf[5] >> 5) & 3;
85  frame_rate_ext_d = (buf[5] & 0x1f);
86  pc->progressive_sequence = buf[1] & (1 << 3);
87  avctx->has_b_frames= !(buf[5] >> 7);
88 
89  pc->width |=(horiz_size_ext << 12);
90  pc->height |=( vert_size_ext << 12);
91  avctx->bit_rate += (bit_rate_ext << 18) * 400;
92  if(did_set_size)
93  ff_set_dimensions(avctx, pc->width, pc->height);
94  avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
95  avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
97  }
98  break;
99  case 0x8: /* picture coding extension */
100  if (bytes_left >= 5) {
101  top_field_first = buf[3] & (1 << 7);
102  repeat_first_field = buf[3] & (1 << 1);
103  progressive_frame = buf[4] & (1 << 7);
104 
105  /* check if we must repeat the frame */
106  s->repeat_pict = 1;
107  if (repeat_first_field) {
108  if (pc->progressive_sequence) {
109  if (top_field_first)
110  s->repeat_pict = 5;
111  else
112  s->repeat_pict = 3;
113  } else if (progressive_frame) {
114  s->repeat_pict = 2;
115  }
116  }
117 
118  if (!pc->progressive_sequence) {
119  if (top_field_first)
121  else
123  } else
125  }
126  break;
127  }
128  }
129  break;
130  case -1:
131  goto the_end;
132  default:
133  /* we stop parsing when we encounter a slice. It ensures
134  that this function takes a negligible amount of time */
135  if (start_code >= SLICE_MIN_START_CODE &&
136  start_code <= SLICE_MAX_START_CODE)
137  goto the_end;
138  break;
139  }
140  }
141  the_end: ;
142 }
143 
145  AVCodecContext *avctx,
146  const uint8_t **poutbuf, int *poutbuf_size,
147  const uint8_t *buf, int buf_size)
148 {
149  struct MpvParseContext *pc1 = s->priv_data;
150  ParseContext *pc= &pc1->pc;
151  int next;
152 
154  next= buf_size;
155  }else{
156  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
157 
158  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
159  *poutbuf = NULL;
160  *poutbuf_size = 0;
161  return buf_size;
162  }
163 
164  }
165  /* we have a full frame : we just parse the first few MPEG headers
166  to have the full timing information. The time take by this
167  function should be negligible for uncorrupted streams */
168  mpegvideo_extract_headers(s, avctx, buf, buf_size);
169  av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
170  s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
171 
172  *poutbuf = buf;
173  *poutbuf_size = buf_size;
174  return next;
175 }
176 
177 static int mpegvideo_split(AVCodecContext *avctx,
178  const uint8_t *buf, int buf_size)
179 {
180  int i;
181  uint32_t state= -1;
182 
183  for(i=0; i<buf_size; i++){
184  state= (state<<8) | buf[i];
185  if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
186  return i-3;
187  }
188  return 0;
189 }
190 
193  .priv_data_size = sizeof(struct MpvParseContext),
194  .parser_parse = mpegvideo_parse,
195  .parser_close = ff_parse_close,
196  .split = mpegvideo_split,
197 };
#define SLICE_MAX_START_CODE
Definition: cavs.h:32
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 e.g.
Definition: avcodec.h:1228
int ff_set_dimensions(AVCodecContext *s, int width, int height)
Check that the provided frame dimensions are valid and set them on the codec context.
Definition: utils.c:133
enum AVFieldOrder field_order
Definition: avcodec.h:3794
int num
numerator
Definition: rational.h:44
int codec_ids[5]
Definition: avcodec.h:3816
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:85
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:1169
uint8_t
int has_b_frames
Size of the frame reordering buffer in the decoder.
Definition: avcodec.h:1333
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:217
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:287
int bit_rate
the average bitrate
Definition: avcodec.h:1108
int width
picture width / height.
Definition: avcodec.h:1218
#define EXT_START_CODE
Definition: cavs.h:33
preferred ID for MPEG-1/2 video decoding
Definition: avcodec.h:110
NULL
Definition: eval.c:55
AVRational frame_rate
enum AVCodecID codec_id
Definition: avcodec.h:1061
main external API structure.
Definition: avcodec.h:1044
int coded_height
Definition: avcodec.h:1228
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:179
AVCodecParser ff_mpegvideo_parser
static uint32_t state
Definition: trasher.c:27
const uint8_t * avpriv_find_start_code(const uint8_t *restrict p, const uint8_t *end, uint32_t *restrict state)
Definition: utils.c:2385
static void mpegvideo_extract_headers(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
common internal api header.
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:3694
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:82
int repeat_pict
This field is used for proper frame duration computation in lavf.
Definition: avcodec.h:3678
#define PICTURE_START_CODE
Definition: mpegvideo.h:84
const AVRational ff_mpeg12_frame_rate_tab[16]
Definition: mpeg12data.c:308