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 "parser.h"
24 #include "mpeg12.h"
25 #include "internal.h"
26 
31  int width, height;
32 };
33 
34 #if !FF_API_FLAG_TRUNCATED
35 /**
36  * Find the end of the current frame in the bitstream.
37  * @return the position of the first byte of the next frame, or -1
38  */
39 static int mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf,
40  int buf_size, AVCodecParserContext *s)
41 {
42  int i;
43  uint32_t state = pc->state;
44 
45  /* EOF considered as end of frame */
46  if (buf_size == 0)
47  return 0;
48 
49 /*
50  0 frame start -> 1/4
51  1 first_SEQEXT -> 0/2
52  2 first field start -> 3/0
53  3 second_SEQEXT -> 2/0
54  4 searching end
55 */
56 
57  for (i = 0; i < buf_size; i++) {
58  av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
59  if (pc->frame_start_found & 1) {
60  if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
61  pc->frame_start_found--;
62  else if (state == EXT_START_CODE + 2) {
63  if ((buf[i] & 3) == 3)
64  pc->frame_start_found = 0;
65  else
66  pc->frame_start_found = (pc->frame_start_found + 1) & 3;
67  }
68  state++;
69  } else {
70  i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
72  i++;
73  pc->frame_start_found = 4;
74  }
75  if (state == SEQ_END_CODE) {
76  pc->frame_start_found = 0;
77  pc->state = -1;
78  return i + 1;
79  }
80  if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
81  pc->frame_start_found = 0;
82  if (pc->frame_start_found < 4 && state == EXT_START_CODE)
83  pc->frame_start_found++;
84  if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
85  if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
86  pc->frame_start_found = 0;
87  pc->state = -1;
88  return i - 3;
89  }
90  }
91  if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
92  ff_fetch_timestamp(s, i - 3, 1, i > 3);
93  }
94  }
95  }
96  pc->state = state;
97  return END_NOT_FOUND;
98 }
99 #endif
100 
102  AVCodecContext *avctx,
103  const uint8_t *buf, int buf_size)
104 {
105  struct MpvParseContext *pc = s->priv_data;
106  const uint8_t *buf_end = buf + buf_size;
107  uint32_t start_code;
108  int frame_rate_index, ext_type, bytes_left;
109  int frame_rate_ext_n, frame_rate_ext_d;
110  int top_field_first, repeat_first_field, progressive_frame;
111  int horiz_size_ext, vert_size_ext, bit_rate_ext;
112  int did_set_size=0;
113  int set_dim_ret = 0;
114  int bit_rate = 0;
115  int vbv_delay = 0;
116  int chroma_format;
118 //FIXME replace the crap with get_bits()
119  s->repeat_pict = 0;
120 
121  while (buf < buf_end) {
122  start_code= -1;
123  buf= avpriv_find_start_code(buf, buf_end, &start_code);
124  bytes_left = buf_end - buf;
125  switch(start_code) {
126  case PICTURE_START_CODE:
127  if (bytes_left >= 2) {
128  s->pict_type = (buf[1] >> 3) & 7;
129  if (bytes_left >= 4)
130  vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
131  }
132  break;
133  case SEQ_START_CODE:
134  if (bytes_left >= 7) {
135  pc->width = (buf[0] << 4) | (buf[1] >> 4);
136  pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
137  if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
138  set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
139  did_set_size=1;
140  }
142  frame_rate_index = buf[3] & 0xf;
143  pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
144  bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
146  avctx->ticks_per_frame = 1;
147  }
148  break;
149  case EXT_START_CODE:
150  if (bytes_left >= 1) {
151  ext_type = (buf[0] >> 4);
152  switch(ext_type) {
153  case 0x1: /* sequence extension */
154  if (bytes_left >= 6) {
155  horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
156  vert_size_ext = (buf[2] >> 5) & 3;
157  bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
158  frame_rate_ext_n = (buf[5] >> 5) & 3;
159  frame_rate_ext_d = (buf[5] & 0x1f);
160  pc->progressive_sequence = buf[1] & (1 << 3);
161  avctx->has_b_frames= !(buf[5] >> 7);
162 
163  chroma_format = (buf[1] >> 1) & 3;
164  switch (chroma_format) {
165  case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
166  case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
167  case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
168  }
169 
170  pc->width = (pc->width & 0xFFF) | (horiz_size_ext << 12);
171  pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
172  bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
173  if(did_set_size)
174  set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
175  avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
176  avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
178  avctx->ticks_per_frame = 2;
179  }
180  break;
181  case 0x8: /* picture coding extension */
182  if (bytes_left >= 5) {
183  top_field_first = buf[3] & (1 << 7);
184  repeat_first_field = buf[3] & (1 << 1);
185  progressive_frame = buf[4] & (1 << 7);
186 
187  /* check if we must repeat the frame */
188  s->repeat_pict = 1;
189  if (repeat_first_field) {
190  if (pc->progressive_sequence) {
191  if (top_field_first)
192  s->repeat_pict = 5;
193  else
194  s->repeat_pict = 3;
195  } else if (progressive_frame) {
196  s->repeat_pict = 2;
197  }
198  }
199 
200  if (!pc->progressive_sequence && !progressive_frame) {
201  if (top_field_first)
202  s->field_order = AV_FIELD_TT;
203  else
204  s->field_order = AV_FIELD_BB;
205  } else
206  s->field_order = AV_FIELD_PROGRESSIVE;
207  }
208  break;
209  }
210  }
211  break;
212  case -1:
213  goto the_end;
214  default:
215  /* we stop parsing when we encounter a slice. It ensures
216  that this function takes a negligible amount of time */
219  goto the_end;
220  break;
221  }
222  }
223  the_end:
224  if (set_dim_ret < 0)
225  av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
226 
227  if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
228  avctx->rc_max_rate = 400LL*bit_rate;
229  }
230  if (bit_rate &&
231  ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
232  avctx->bit_rate = 400LL*bit_rate;
233  }
234 
235  if (pix_fmt != AV_PIX_FMT_NONE) {
236  s->format = pix_fmt;
237  s->width = pc->width;
238  s->height = pc->height;
239  s->coded_width = FFALIGN(pc->width, 16);
240  s->coded_height = FFALIGN(pc->height, 16);
241  }
242 
243 #if FF_API_AVCTX_TIMEBASE
244  if (avctx->framerate.num)
245  avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
246 #endif
247 }
248 
250  AVCodecContext *avctx,
251  const uint8_t **poutbuf, int *poutbuf_size,
252  const uint8_t *buf, int buf_size)
253 {
254  struct MpvParseContext *pc1 = s->priv_data;
255  ParseContext *pc= &pc1->pc;
256  int next;
257 
258  if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
259  next= buf_size;
260  }else{
261 #if FF_API_FLAG_TRUNCATED
262  next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
263 #else
264  next = mpeg1_find_frame_end(pc, buf, buf_size, s);
265 #endif
266 
267  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
268  *poutbuf = NULL;
269  *poutbuf_size = 0;
270  return buf_size;
271  }
272 
273  }
274  /* we have a full frame : we just parse the first few MPEG headers
275  to have the full timing information. The time take by this
276  function should be negligible for uncorrupted streams */
277  mpegvideo_extract_headers(s, avctx, buf, buf_size);
278  ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
279  s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
280 
281  *poutbuf = buf;
282  *poutbuf_size = buf_size;
283  return next;
284 }
285 
287 {
288  s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
289  return 0;
290 }
291 
294  .priv_data_size = sizeof(struct MpvParseContext),
295  .parser_init = mpegvideo_parse_init,
296  .parser_parse = mpegvideo_parse,
297  .parser_close = ff_parse_close,
298 };
AVPixelFormat
AVPixelFormat
Pixel format.
Definition: pixfmt.h:64
MpvParseContext::height
int height
Definition: mpegvideo_parser.c:31
SEQ_END_CODE
#define SEQ_END_CODE
Definition: mpeg12.h:29
EXT_START_CODE
#define EXT_START_CODE
Definition: cavs.h:35
MpvParseContext::frame_rate
AVRational frame_rate
Definition: mpegvideo_parser.c:29
SLICE_MAX_START_CODE
#define SLICE_MAX_START_CODE
Definition: cavs.h:34
start_code
static const uint8_t start_code[]
Definition: videotoolboxenc.c:191
ff_parse_close
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:286
internal.h
MpvParseContext::width
int width
Definition: mpegvideo_parser.c:31
avpriv_find_start_code
const uint8_t * avpriv_find_start_code(const uint8_t *p, const uint8_t *end, uint32_t *state)
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:30
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:86
AVCodecContext::framerate
AVRational framerate
Definition: avcodec.h:1710
ParseContext
Definition: parser.h:28
AV_FIELD_TT
@ AV_FIELD_TT
Definition: codec_par.h:39
AVCodecContext::coded_height
int coded_height
Definition: avcodec.h:571
AVRational::num
int num
Numerator.
Definition: rational.h:59
mpeg12.h
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
AVCodecContext::has_b_frames
int has_b_frames
Size of the frame reordering buffer in the decoder.
Definition: avcodec.h:679
s
#define s(width, name)
Definition: cbs_vp9.c:257
ff_mpegvideo_parser
const AVCodecParser ff_mpegvideo_parser
Definition: mpegvideo_parser.c:292
AVCodecContext::ticks_per_frame
int ticks_per_frame
For some codecs, the time base is closer to the field rate than the frame rate.
Definition: avcodec.h:515
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:249
pix_fmt
static enum AVPixelFormat pix_fmt
Definition: demuxing_decoding.c:41
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:66
AVCodecContext::rc_max_rate
int64_t rc_max_rate
maximum bitrate
Definition: avcodec.h:1194
AVCodecContext::codec_id
enum AVCodecID codec_id
Definition: avcodec.h:393
NULL
#define NULL
Definition: coverity.c:32
SLICE_MIN_START_CODE
#define SLICE_MIN_START_CODE
Definition: mpeg12.h:33
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
state
static struct @317 state
AVCodecContext::bit_rate
int64_t bit_rate
the average bitrate
Definition: avcodec.h:433
ParseContext::frame_start_found
int frame_start_found
Definition: parser.h:34
AV_CODEC_ID_MPEG1VIDEO
@ AV_CODEC_ID_MPEG1VIDEO
Definition: codec_id.h:51
ff_dlog
#define ff_dlog(a,...)
Definition: tableprint_vlc.h:29
ff_mpeg1_find_frame_end
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:176
AVCodecContext::time_base
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
Definition: avcodec.h:506
mpegvideo_extract_headers
static void mpegvideo_extract_headers(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
Definition: mpegvideo_parser.c:101
AVCodecParser::codec_ids
int codec_ids[7]
Definition: avcodec.h:2935
PICTURE_START_CODE
#define PICTURE_START_CODE
Definition: mpeg12.h:32
AV_PICTURE_TYPE_NONE
@ AV_PICTURE_TYPE_NONE
Undefined.
Definition: avutil.h:273
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:201
AV_FIELD_BB
@ AV_FIELD_BB
Definition: codec_par.h:40
i
int i
Definition: input.c:406
PARSER_FLAG_COMPLETE_FRAMES
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:2809
av_assert1
#define av_assert1(cond)
assert() equivalent, that does not lie in speed critical code.
Definition: avassert.h:53
av_inv_q
static av_always_inline AVRational av_inv_q(AVRational q)
Invert a rational.
Definition: rational.h:159
parser.h
AVCodecContext::height
int height
Definition: avcodec.h:556
MpvParseContext::pc
ParseContext pc
Definition: mpegvideo_parser.c:28
MpvParseContext
Definition: mpegvideo_parser.c:27
AVCodecParserContext
Definition: avcodec.h:2775
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:30
AVCodecContext
main external API structure.
Definition: avcodec.h:383
AVRational::den
int den
Denominator.
Definition: rational.h:60
AV_PIX_FMT_NONE
@ AV_PIX_FMT_NONE
Definition: pixfmt.h:65
av_mul_q
AVRational av_mul_q(AVRational b, AVRational c)
Multiply two rationals.
Definition: rational.c:80
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:71
AVCodecContext::coded_width
int coded_width
Bitstream width / height, may be different from width/height e.g.
Definition: avcodec.h:571
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:70
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:86
AV_FIELD_PROGRESSIVE
@ AV_FIELD_PROGRESSIVE
Definition: codec_par.h:38
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:286
AVCodecParser
Definition: avcodec.h:2934
AVCodecContext::width
int width
picture width / height.
Definition: avcodec.h:556
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
AV_CODEC_ID_MPEG2VIDEO
@ AV_CODEC_ID_MPEG2VIDEO
preferred ID for MPEG-1/2 video decoding
Definition: codec_id.h:52