Libav
mpegvideo_parser.c
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1 /*
2  * MPEG-1 / MPEG-2 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  int chroma_format;
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  }
61  break;
62  case SEQ_START_CODE:
63  if (bytes_left >= 7) {
64  pc->width = (buf[0] << 4) | (buf[1] >> 4);
65  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
66  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
67  ff_set_dimensions(avctx, pc->width, pc->height);
68  did_set_size=1;
69  }
70  pix_fmt = AV_PIX_FMT_YUV420P;
71  frame_rate_index = buf[3] & 0xf;
72  pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
73  avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
75  }
76  break;
77  case EXT_START_CODE:
78  if (bytes_left >= 1) {
79  ext_type = (buf[0] >> 4);
80  switch(ext_type) {
81  case 0x1: /* sequence extension */
82  if (bytes_left >= 6) {
83  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
84  vert_size_ext = (buf[2] >> 5) & 3;
85  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
86  frame_rate_ext_n = (buf[5] >> 5) & 3;
87  frame_rate_ext_d = (buf[5] & 0x1f);
88  pc->progressive_sequence = buf[1] & (1 << 3);
89  avctx->has_b_frames= !(buf[5] >> 7);
90 
91  chroma_format = (buf[1] >> 1) & 3;
92  switch (chroma_format) {
93  case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
94  case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
95  case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
96  }
97 
98  pc->width |=(horiz_size_ext << 12);
99  pc->height |=( vert_size_ext << 12);
100 
101  bit_rate_ext <<= 18;
102  if (bit_rate_ext < INT_MAX / 400 &&
103  bit_rate_ext * 400 < INT_MAX - avctx->bit_rate) {
104  avctx->bit_rate += bit_rate_ext * 400;
105  } else
106  avctx->bit_rate = 0;
107 
108  if(did_set_size)
109  ff_set_dimensions(avctx, pc->width, pc->height);
110  avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1) * 2;
111  avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
113  }
114  break;
115  case 0x8: /* picture coding extension */
116  if (bytes_left >= 5) {
117  top_field_first = buf[3] & (1 << 7);
118  repeat_first_field = buf[3] & (1 << 1);
119  progressive_frame = buf[4] & (1 << 7);
120 
121  /* check if we must repeat the frame */
122  s->repeat_pict = 1;
123  if (repeat_first_field) {
124  if (pc->progressive_sequence) {
125  if (top_field_first)
126  s->repeat_pict = 5;
127  else
128  s->repeat_pict = 3;
129  } else if (progressive_frame) {
130  s->repeat_pict = 2;
131  }
132  }
133 
134  if (!pc->progressive_sequence) {
135  if (top_field_first)
137  else
139  } else
141  }
142  break;
143  }
144  }
145  break;
146  case -1:
147  goto the_end;
148  default:
149  /* we stop parsing when we encounter a slice. It ensures
150  that this function takes a negligible amount of time */
151  if (start_code >= SLICE_MIN_START_CODE &&
152  start_code <= SLICE_MAX_START_CODE)
153  goto the_end;
154  break;
155  }
156  }
157  the_end: ;
158 
159  if (pix_fmt != AV_PIX_FMT_NONE) {
160  s->format = pix_fmt;
161  s->width = pc->width;
162  s->height = pc->height;
163  s->coded_width = FFALIGN(pc->width, 16);
164  s->coded_height = FFALIGN(pc->height, 16);
165  }
166 
167 #if FF_API_AVCTX_TIMEBASE
168  if (avctx->framerate.num)
169  avctx->time_base = av_inv_q(avctx->framerate);
170 #endif
171 }
172 
174  AVCodecContext *avctx,
175  const uint8_t **poutbuf, int *poutbuf_size,
176  const uint8_t *buf, int buf_size)
177 {
178  struct MpvParseContext *pc1 = s->priv_data;
179  ParseContext *pc= &pc1->pc;
180  int next;
181 
183  next= buf_size;
184  }else{
185  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
186 
187  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
188  *poutbuf = NULL;
189  *poutbuf_size = 0;
190  return buf_size;
191  }
192 
193  }
194  /* we have a full frame : we just parse the first few MPEG headers
195  to have the full timing information. The time take by this
196  function should be negligible for uncorrupted streams */
197  mpegvideo_extract_headers(s, avctx, buf, buf_size);
198  ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
199  s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
200 
201  *poutbuf = buf;
202  *poutbuf_size = buf_size;
203  return next;
204 }
205 
206 static int mpegvideo_split(AVCodecContext *avctx,
207  const uint8_t *buf, int buf_size)
208 {
209  int i;
210  uint32_t state= -1;
211 
212  for(i=0; i<buf_size; i++){
213  state= (state<<8) | buf[i];
214  if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
215  return i-3;
216  }
217  return 0;
218 }
219 
222  .priv_data_size = sizeof(struct MpvParseContext),
223  .parser_parse = mpegvideo_parse,
224  .parser_close = ff_parse_close,
225  .split = mpegvideo_split,
226 };
AVRational framerate
Definition: avcodec.h:3063
#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:1595
planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)
Definition: pixfmt.h:64
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:134
int width
Dimensions of the decoded video intended for presentation.
Definition: avcodec.h:4508
enum AVFieldOrder field_order
Definition: avcodec.h:4485
int num
numerator
Definition: rational.h:44
int codec_ids[5]
Definition: avcodec.h:4529
int coded_width
Dimensions of the coded video.
Definition: avcodec.h:4514
#define SLICE_MIN_START_CODE
Definition: mpegvideo.h:68
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:1535
uint8_t
#define FFALIGN(x, a)
Definition: macros.h:48
int has_b_frames
Size of the frame reordering buffer in the decoder.
Definition: avcodec.h:1715
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:227
planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
Definition: pixfmt.h:63
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:297
int bit_rate
the average bitrate
Definition: avcodec.h:1473
int width
picture width / height.
Definition: avcodec.h:1580
#define EXT_START_CODE
Definition: cavs.h:33
enum AVPixelFormat pix_fmt
Definition: movenc.c:853
preferred ID for MPEG-1/2 video decoding
Definition: avcodec.h:198
NULL
Definition: eval.c:55
AVRational frame_rate
#define ff_dlog(ctx,...)
Definition: internal.h:60
enum AVCodecID codec_id
Definition: avcodec.h:1426
main external API structure.
Definition: avcodec.h:1409
int coded_height
Definition: avcodec.h:1595
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:180
AVCodecParser ff_mpegvideo_parser
static av_always_inline AVRational av_inv_q(AVRational q)
Invert a rational.
Definition: rational.h:122
const uint8_t * avpriv_find_start_code(const uint8_t *restrict p, const uint8_t *end, uint32_t *restrict state)
Definition: utils.c:2707
static void mpegvideo_extract_headers(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
static struct @174 state
planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
Definition: pixfmt.h:59
common internal api header.
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:4396
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:65
int format
The format of the coded data, corresponds to enum AVPixelFormat for video and for enum AVSampleFormat...
Definition: avcodec.h:4525
int repeat_pict
This field is used for proper frame duration computation in lavf.
Definition: avcodec.h:4380
#define PICTURE_START_CODE
Definition: mpegvideo.h:67
AVPixelFormat
Pixel format.
Definition: pixfmt.h:57
const AVRational ff_mpeg12_frame_rate_tab[]