FFmpeg
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 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 "libavutil/avassert.h"
24 #include "decode.h"
25 #include "parser.h"
26 #include "mpeg12.h"
27 #include "mpeg12data.h"
28 #include "startcode.h"
29 
34  int width, height;
35 };
36 
37 /**
38  * Find the end of the current frame in the bitstream.
39  * @return the position of the first byte of the next frame, or -1
40  */
41 static int mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf,
42  int buf_size, AVCodecParserContext *s)
43 {
44  int i;
45  uint32_t state = pc->state;
46 
47  /* EOF considered as end of frame */
48  if (buf_size == 0)
49  return 0;
50 
51 /*
52  0 frame start -> 1/4
53  1 first_SEQEXT -> 0/2
54  2 first field start -> 3/0
55  3 second_SEQEXT -> 2/0
56  4 searching end
57 */
58 
59  for (i = 0; i < buf_size; i++) {
60  av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
61  if (pc->frame_start_found & 1) {
62  if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
63  pc->frame_start_found--;
64  else if (state == EXT_START_CODE + 2) {
65  if ((buf[i] & 3) == 3)
66  pc->frame_start_found = 0;
67  else
68  pc->frame_start_found = (pc->frame_start_found + 1) & 3;
69  }
70  state++;
71  } else {
72  i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
74  i++;
75  pc->frame_start_found = 4;
76  }
77  if (state == SEQ_END_CODE) {
78  pc->frame_start_found = 0;
79  pc->state = -1;
80  return i + 1;
81  }
82  if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
83  pc->frame_start_found = 0;
84  if (pc->frame_start_found < 4 && state == EXT_START_CODE)
85  pc->frame_start_found++;
86  if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
87  if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
88  pc->frame_start_found = 0;
89  pc->state = -1;
90  return i - 3;
91  }
92  }
93  if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
94  ff_fetch_timestamp(s, i - 3, 1, i > 3);
95  }
96  }
97  }
98  pc->state = state;
99  return END_NOT_FOUND;
100 }
101 
103  AVCodecContext *avctx,
104  const uint8_t *buf, int buf_size)
105 {
106  struct MpvParseContext *pc = s->priv_data;
107  const uint8_t *buf_end = buf + buf_size;
108  int bytes_left;
109  int did_set_size=0;
110  int set_dim_ret = 0;
111  int bit_rate = 0;
112  int vbv_delay = 0;
114 
115  // number of picture coding extensions (i.e. MPEG2 pictures)
116  // in this packet - should be 1 or 2
117  int nb_pic_ext = 0;
118  // when there are two pictures in the packet this indicates
119  // which field is in the first of them
121 
122 //FIXME replace the crap with get_bits()
123  while (buf < buf_end) {
124  uint32_t start_code = -1;
125  buf= avpriv_find_start_code(buf, buf_end, &start_code);
126  bytes_left = buf_end - buf;
127  switch(start_code) {
128  case PICTURE_START_CODE:
129  if (bytes_left >= 2) {
130  s->pict_type = (buf[1] >> 3) & 7;
131  if (bytes_left >= 4)
132  vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
133  }
134  break;
135  case SEQ_START_CODE:
136  if (bytes_left >= 7) {
137  int frame_rate_index;
138 
139  pc->width = (buf[0] << 4) | (buf[1] >> 4);
140  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
141  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
142  set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
143  did_set_size=1;
144  }
146  frame_rate_index = buf[3] & 0xf;
147  pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
148  bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
150 #if FF_API_TICKS_PER_FRAME
152  avctx->ticks_per_frame = 1;
154 #endif
155  }
156  break;
157  case EXT_START_CODE:
158  if (bytes_left >= 1) {
159  switch (buf[0] >> 4) { // ext_type
160  case 0x1: /* sequence extension */
161  if (bytes_left >= 6) {
162  int horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
163  int vert_size_ext = (buf[2] >> 5) & 3;
164  int bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
165  int frame_rate_ext_n = (buf[5] >> 5) & 3;
166  int frame_rate_ext_d = (buf[5] & 0x1f);
167  pc->progressive_sequence = buf[1] & (1 << 3);
168  avctx->has_b_frames= !(buf[5] >> 7);
169 
170  switch ((buf[1] >> 1) & 3) { // chroma_format
171  case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
172  case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
173  case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
174  }
175 
176  pc->width = (pc->width & 0xFFF) | (horiz_size_ext << 12);
177  pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
178  bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
179  if(did_set_size)
180  set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
181  avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
182  avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
184 #if FF_API_TICKS_PER_FRAME
186  avctx->ticks_per_frame = 2;
188 #endif
189  }
190  break;
191  case 0x8: /* picture coding extension */
192  if (bytes_left >= 5) {
193  int top_field_first = buf[3] & (1 << 7);
194  int repeat_first_field = buf[3] & (1 << 1);
195  int progressive_frame = buf[4] & (1 << 7);
196 
197  /* check if we must repeat the frame */
198  s->repeat_pict = 1;
199  if (repeat_first_field) {
200  if (pc->progressive_sequence) {
201  if (top_field_first)
202  s->repeat_pict = 5;
203  else
204  s->repeat_pict = 3;
205  } else if (progressive_frame) {
206  s->repeat_pict = 2;
207  }
208  }
209 
210  if (!pc->progressive_sequence && !progressive_frame) {
211  if (top_field_first)
212  s->field_order = AV_FIELD_TT;
213  else
214  s->field_order = AV_FIELD_BB;
215  } else
216  s->field_order = AV_FIELD_PROGRESSIVE;
217 
218  s->picture_structure = buf[2] & 3;
219 
220  if (!nb_pic_ext) {
221  // remember parity of the first field for the case
222  // when there are 2 fields in packet
223  switch (s->picture_structure) {
226  }
227  }
228 
229  nb_pic_ext++;
230  }
231  break;
232  }
233  }
234  break;
235  case -1:
236  goto the_end;
237  default:
238  /* we stop parsing when we encounter a slice. It ensures
239  that this function takes a negligible amount of time */
242  goto the_end;
243  break;
244  }
245  }
246  the_end:
247  if (set_dim_ret < 0)
248  av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
249 
250  if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate && bit_rate != 0x3FFFF) {
251  avctx->rc_max_rate = 400LL*bit_rate;
252  }
253  if (bit_rate &&
254  ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
255  avctx->bit_rate = 400LL*bit_rate;
256  }
257 
258  if (pix_fmt != AV_PIX_FMT_NONE) {
259  s->format = pix_fmt;
260  s->width = pc->width;
261  s->height = pc->height;
262  s->coded_width = FFALIGN(pc->width, 16);
263  s->coded_height = FFALIGN(pc->height, 16);
264  }
265 
266  if (avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO || nb_pic_ext > 1) {
267  s->repeat_pict = 1;
268  s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
269  s->field_order = nb_pic_ext > 1 ? first_field : AV_FIELD_PROGRESSIVE;
270  }
271 }
272 
274  AVCodecContext *avctx,
275  const uint8_t **poutbuf, int *poutbuf_size,
276  const uint8_t *buf, int buf_size)
277 {
278  struct MpvParseContext *pc1 = s->priv_data;
279  ParseContext *pc= &pc1->pc;
280  int next;
281 
282  if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
283  next= buf_size;
284  }else{
285  next = mpeg1_find_frame_end(pc, buf, buf_size, s);
286 
287  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
288  *poutbuf = NULL;
289  *poutbuf_size = 0;
290  return buf_size;
291  }
292 
293  }
294  /* we have a full frame : we just parse the first few MPEG headers
295  to have the full timing information. The time take by this
296  function should be negligible for uncorrupted streams */
297  mpegvideo_extract_headers(s, avctx, buf, buf_size);
298  ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
299  s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
300 
301  *poutbuf = buf;
302  *poutbuf_size = buf_size;
303  return next;
304 }
305 
307 {
308  s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
309  return 0;
310 }
311 
314  .priv_data_size = sizeof(struct MpvParseContext),
315  .parser_init = mpegvideo_parse_init,
316  .parser_parse = mpegvideo_parse,
317  .parser_close = ff_parse_close,
318 };
FF_ENABLE_DEPRECATION_WARNINGS
#define FF_ENABLE_DEPRECATION_WARNINGS
Definition: internal.h:73
AVPixelFormat
AVPixelFormat
Pixel format.
Definition: pixfmt.h:71
MpvParseContext::height
int height
Definition: mpegvideo_parser.c:34
SEQ_END_CODE
#define SEQ_END_CODE
Definition: mpeg12.h:28
AV_FIELD_PROGRESSIVE
@ AV_FIELD_PROGRESSIVE
Definition: defs.h:200
EXT_START_CODE
#define EXT_START_CODE
Definition: cavs.h:39
MpvParseContext::frame_rate
AVRational frame_rate
Definition: mpegvideo_parser.c:32
SLICE_MAX_START_CODE
#define SLICE_MAX_START_CODE
Definition: cavs.h:38
start_code
static const uint8_t start_code[]
Definition: videotoolboxenc.c:221
ff_parse_close
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:289
MpvParseContext::width
int width
Definition: mpegvideo_parser.c:34
ff_set_dimensions
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:94
ParseContext::state
uint32_t state
contains the last few bytes in MSB order
Definition: parser.h:33
SEQ_START_CODE
#define SEQ_START_CODE
Definition: mpeg12.h:29
ff_fetch_timestamp
void ff_fetch_timestamp(AVCodecParserContext *s, int off, int remove, int fuzzy)
Fetch timestamps for a specific byte within the current access unit.
Definition: parser.c:84
AVCodecContext::framerate
AVRational framerate
Definition: avcodec.h:560
AV_FIELD_TT
@ AV_FIELD_TT
Top coded_first, top displayed first.
Definition: defs.h:201
ParseContext
Definition: parser.h:28
AVCodecContext::coded_height
int coded_height
Definition: avcodec.h:633
AVRational::num
int num
Numerator.
Definition: rational.h:59
avassert.h
AV_PICTURE_STRUCTURE_FRAME
@ AV_PICTURE_STRUCTURE_FRAME
coded as frame
Definition: avcodec.h:2705
mpeg12.h
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
AV_FIELD_UNKNOWN
@ AV_FIELD_UNKNOWN
Definition: defs.h:199
AVCodecContext::has_b_frames
int has_b_frames
Size of the frame reordering buffer in the decoder.
Definition: avcodec.h:723
s
#define s(width, name)
Definition: cbs_vp9.c:198
ff_mpegvideo_parser
const AVCodecParser ff_mpegvideo_parser
Definition: mpegvideo_parser.c:312
pix_fmt
static enum AVPixelFormat pix_fmt
Definition: demux_decode.c:41
av_q2d
static double av_q2d(AVRational a)
Convert an AVRational to a double.
Definition: rational.h:104
mpegvideo_parse
static int mpegvideo_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: mpegvideo_parser.c:273
decode.h
AV_PIX_FMT_YUV420P
@ AV_PIX_FMT_YUV420P
planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
Definition: pixfmt.h:73
AVCodecContext::rc_max_rate
int64_t rc_max_rate
maximum bitrate
Definition: avcodec.h:1292
AVCodecContext::codec_id
enum AVCodecID codec_id
Definition: avcodec.h:455
AV_PICTURE_STRUCTURE_BOTTOM_FIELD
@ AV_PICTURE_STRUCTURE_BOTTOM_FIELD
coded as bottom field
Definition: avcodec.h:2704
NULL
#define NULL
Definition: coverity.c:32
SLICE_MIN_START_CODE
#define SLICE_MIN_START_CODE
Definition: mpeg12.h:32
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
AV_PICTURE_STRUCTURE_TOP_FIELD
@ AV_PICTURE_STRUCTURE_TOP_FIELD
coded as top field
Definition: avcodec.h:2703
AVCodecContext::bit_rate
int64_t bit_rate
the average bitrate
Definition: avcodec.h:495
ParseContext::frame_start_found
int frame_start_found
Definition: parser.h:34
avpriv_find_start_code
const uint8_t * avpriv_find_start_code(const uint8_t *p, const uint8_t *end, uint32_t *state)
AV_CODEC_ID_MPEG1VIDEO
@ AV_CODEC_ID_MPEG1VIDEO
Definition: codec_id.h:53
ff_dlog
#define ff_dlog(a,...)
Definition: tableprint_vlc.h:28
startcode.h
mpegvideo_extract_headers
static void mpegvideo_extract_headers(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
Definition: mpegvideo_parser.c:102
AVCodecParser::codec_ids
int codec_ids[7]
Definition: avcodec.h:2868
mpeg1_find_frame_end
static int 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: mpegvideo_parser.c:41
PICTURE_START_CODE
#define PICTURE_START_CODE
Definition: mpeg12.h:31
AV_PICTURE_TYPE_NONE
@ AV_PICTURE_TYPE_NONE
Undefined.
Definition: avutil.h:278
ff_combine_frame
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:203
PARSER_FLAG_COMPLETE_FRAMES
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:2742
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:256
AV_FIELD_BB
@ AV_FIELD_BB
Bottom coded first, bottom displayed first.
Definition: defs.h:202
av_assert1
#define av_assert1(cond)
assert() equivalent, that does not lie in speed critical code.
Definition: avassert.h:56
state
static struct @416 state
parser.h
AVCodecContext::height
int height
Definition: avcodec.h:618
MpvParseContext::pc
ParseContext pc
Definition: mpegvideo_parser.c:31
MpvParseContext
Definition: mpegvideo_parser.c:30
AVCodecParserContext
Definition: avcodec.h:2708
ff_mpeg12_frame_rate_tab
const AVRational ff_mpeg12_frame_rate_tab[]
Definition: mpeg12framerate.c:24
MpvParseContext::progressive_sequence
int progressive_sequence
Definition: mpegvideo_parser.c:33
mpeg12data.h
AVCodecContext
main external API structure.
Definition: avcodec.h:445
AVRational::den
int den
Denominator.
Definition: rational.h:60
AV_PIX_FMT_NONE
@ AV_PIX_FMT_NONE
Definition: pixfmt.h:72
AVCodecContext::ticks_per_frame
attribute_deprecated int ticks_per_frame
For some codecs, the time base is closer to the field rate than the frame rate.
Definition: avcodec.h:576
AV_PIX_FMT_YUV444P
@ AV_PIX_FMT_YUV444P
planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)
Definition: pixfmt.h:78
FF_DISABLE_DEPRECATION_WARNINGS
#define FF_DISABLE_DEPRECATION_WARNINGS
Definition: internal.h:72
AVCodecContext::coded_width
int coded_width
Bitstream width / height, may be different from width/height e.g.
Definition: avcodec.h:633
AV_PIX_FMT_YUV422P
@ AV_PIX_FMT_YUV422P
planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
Definition: pixfmt.h:77
END_NOT_FOUND
#define END_NOT_FOUND
Definition: parser.h:40
FFALIGN
#define FFALIGN(x, a)
Definition: macros.h:78
mpegvideo_parse_init
static int mpegvideo_parse_init(AVCodecParserContext *s)
Definition: mpegvideo_parser.c:306
AVCodecParser
Definition: avcodec.h:2867
AVCodecContext::width
int width
picture width / height.
Definition: avcodec.h:618
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
first_field
static int first_field(const struct video_data *s)
Definition: v4l2.c:247
AV_CODEC_ID_MPEG2VIDEO
@ AV_CODEC_ID_MPEG2VIDEO
preferred ID for MPEG-1/2 video decoding
Definition: codec_id.h:54