FFmpeg
gifdec.c
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1 /*
2  * GIF decoder
3  * Copyright (c) 2003 Fabrice Bellard
4  * Copyright (c) 2006 Baptiste Coudurier
5  * Copyright (c) 2012 Vitaliy E Sugrobov
6  *
7  * This file is part of FFmpeg.
8  *
9  * FFmpeg is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * FFmpeg is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with FFmpeg; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 #include "libavutil/imgutils.h"
25 #include "libavutil/opt.h"
26 #include "avcodec.h"
27 #include "bytestream.h"
28 #include "codec_internal.h"
29 #include "internal.h"
30 #include "lzw.h"
31 #include "gif.h"
32 
33 /* This value is intentionally set to "transparent white" color.
34  * It is much better to have white background instead of black
35  * when gif image converted to format which not support transparency.
36  */
37 #define GIF_TRANSPARENT_COLOR 0x00ffffff
38 
39 typedef struct GifState {
40  const AVClass *class;
46  uint32_t bg_color;
50  /* intermediate buffer for storing color indices
51  * obtained from lzw-encoded data stream */
52  uint8_t *idx_line;
54 
55  /* after the frame is displayed, the disposal method is used */
58  /* rectangle describing area that must be disposed */
60  /* depending on disposal method we store either part of the image
61  * drawn on the canvas or background color that
62  * should be used upon disposal */
63  uint32_t * stored_img;
66 
69 
70  /* aux buffers */
71  uint32_t global_palette[256];
72  uint32_t local_palette[256];
73 
75  int keyframe;
77  int trans_color; /**< color value that is used instead of transparent color */
78 } GifState;
79 
80 static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
81 {
82  int i;
83 
84  for (i = 0; i < nb; i++, pal++)
85  *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
86 }
87 
88 static void gif_fill(AVFrame *picture, uint32_t color)
89 {
90  uint32_t *p = (uint32_t *)picture->data[0];
91  uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;
92 
93  for (; p < p_end; p++)
94  *p = color;
95 }
96 
97 static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
98 {
99  const int linesize = picture->linesize[0] / sizeof(uint32_t);
100  const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;
101  const uint32_t *pr, *pb = py + h * linesize;
102  uint32_t *px;
103 
104  for (; py < pb; py += linesize) {
105  px = (uint32_t *)py + l;
106  pr = px + w;
107 
108  for (; px < pr; px++)
109  *px = color;
110  }
111 }
112 
113 static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
114  int linesize, int l, int t, int w, int h)
115 {
116  const int y_start = t * linesize;
117  const uint32_t *src_px,
118  *src_py = src + y_start,
119  *dst_py = dst + y_start;
120  const uint32_t *src_pb = src_py + h * linesize;
121  uint32_t *dst_px;
122 
123  for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
124  src_px = src_py + l;
125  dst_px = (uint32_t *)dst_py + l;
126 
127  memcpy(dst_px, src_px, w * sizeof(uint32_t));
128  }
129 }
130 
132 {
133  int left, top, width, height, bits_per_pixel, code_size, flags, pw;
134  int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size, lzwed_len;
135  uint32_t *ptr, *pal, *px, *pr, *ptr1;
136  int ret;
137  uint8_t *idx;
138 
139  /* At least 9 bytes of Image Descriptor. */
140  if (bytestream2_get_bytes_left(&s->gb) < 9)
141  return AVERROR_INVALIDDATA;
142 
143  left = bytestream2_get_le16u(&s->gb);
144  top = bytestream2_get_le16u(&s->gb);
145  width = bytestream2_get_le16u(&s->gb);
146  height = bytestream2_get_le16u(&s->gb);
147  flags = bytestream2_get_byteu(&s->gb);
148  is_interleaved = flags & 0x40;
149  has_local_palette = flags & 0x80;
150  bits_per_pixel = (flags & 0x07) + 1;
151 
152  ff_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);
153 
154  if (has_local_palette) {
155  pal_size = 1 << bits_per_pixel;
156 
157  if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
158  return AVERROR_INVALIDDATA;
159 
160  gif_read_palette(s, s->local_palette, pal_size);
161  pal = s->local_palette;
162  } else {
163  if (!s->has_global_palette) {
164  av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
165  return AVERROR_INVALIDDATA;
166  }
167 
168  pal = s->global_palette;
169  }
170 
171  if (s->keyframe) {
172  if (s->transparent_color_index == -1 && s->has_global_palette) {
173  /* transparency wasn't set before the first frame, fill with background color */
174  gif_fill(frame, s->bg_color);
175  } else {
176  /* otherwise fill with transparent color.
177  * this is necessary since by default picture filled with 0x80808080. */
178  gif_fill(frame, s->trans_color);
179  }
180  }
181 
182  /* verify that all the image is inside the screen dimensions */
183  if (!width || width > s->screen_width) {
184  av_log(s->avctx, AV_LOG_WARNING, "Invalid image width: %d, truncating.\n", width);
185  width = s->screen_width;
186  }
187  if (left >= s->screen_width) {
188  av_log(s->avctx, AV_LOG_ERROR, "Invalid left position: %d.\n", left);
189  return AVERROR_INVALIDDATA;
190  }
191  if (!height || height > s->screen_height) {
192  av_log(s->avctx, AV_LOG_WARNING, "Invalid image height: %d, truncating.\n", height);
193  height = s->screen_height;
194  }
195  if (top >= s->screen_height) {
196  av_log(s->avctx, AV_LOG_ERROR, "Invalid top position: %d.\n", top);
197  return AVERROR_INVALIDDATA;
198  }
199  if (left + width > s->screen_width) {
200  /* width must be kept around to avoid lzw vs line desync */
201  pw = s->screen_width - left;
202  av_log(s->avctx, AV_LOG_WARNING, "Image too wide by %d, truncating.\n",
203  left + width - s->screen_width);
204  } else {
205  pw = width;
206  }
207  if (top + height > s->screen_height) {
208  /* we don't care about the extra invisible lines */
209  av_log(s->avctx, AV_LOG_WARNING, "Image too high by %d, truncating.\n",
210  top + height - s->screen_height);
211  height = s->screen_height - top;
212  }
213 
214  /* process disposal method */
215  if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {
216  gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
217  } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
218  gif_copy_img_rect(s->stored_img, (uint32_t *)frame->data[0],
219  frame->linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
220  }
221 
222  s->gce_prev_disposal = s->gce_disposal;
223 
224  if (s->gce_disposal != GCE_DISPOSAL_NONE) {
225  s->gce_l = left; s->gce_t = top;
226  s->gce_w = pw; s->gce_h = height;
227 
228  if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {
229  if (s->transparent_color_index >= 0)
230  s->stored_bg_color = s->trans_color;
231  else
232  s->stored_bg_color = s->bg_color;
233  } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
234  av_fast_malloc(&s->stored_img, &s->stored_img_size, frame->linesize[0] * frame->height);
235  if (!s->stored_img)
236  return AVERROR(ENOMEM);
237 
238  gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,
239  frame->linesize[0] / sizeof(uint32_t), left, top, pw, height);
240  }
241  }
242 
243  /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
244  if (bytestream2_get_bytes_left(&s->gb) < 2)
245  return AVERROR_INVALIDDATA;
246 
247  /* now get the image data */
248  code_size = bytestream2_get_byteu(&s->gb);
249  if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
250  bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {
251  av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
252  return ret;
253  }
254 
255  /* read all the image */
256  linesize = frame->linesize[0] / sizeof(uint32_t);
257  ptr1 = (uint32_t *)frame->data[0] + top * linesize + left;
258  ptr = ptr1;
259  pass = 0;
260  y1 = 0;
261  for (y = 0; y < height; y++) {
262  int count = ff_lzw_decode(s->lzw, s->idx_line, width);
263  if (count != width) {
264  if (count)
265  av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");
266  goto decode_tail;
267  }
268 
269  pr = ptr + pw;
270 
271  for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
272  if (*idx != s->transparent_color_index)
273  *px = pal[*idx];
274  }
275 
276  if (is_interleaved) {
277  switch(pass) {
278  default:
279  case 0:
280  case 1:
281  y1 += 8;
282  ptr += linesize * 8;
283  break;
284  case 2:
285  y1 += 4;
286  ptr += linesize * 4;
287  break;
288  case 3:
289  y1 += 2;
290  ptr += linesize * 2;
291  break;
292  }
293  while (y1 >= height) {
294  y1 = 4 >> pass;
295  ptr = ptr1 + linesize * y1;
296  pass++;
297  }
298  } else {
299  ptr += linesize;
300  }
301  }
302 
303  decode_tail:
304  /* read the garbage data until end marker is found */
305  lzwed_len = ff_lzw_decode_tail(s->lzw);
306  bytestream2_skipu(&s->gb, lzwed_len);
307 
308  /* Graphic Control Extension's scope is single frame.
309  * Remove its influence. */
310  s->transparent_color_index = -1;
311  s->gce_disposal = GCE_DISPOSAL_NONE;
312 
313  return 0;
314 }
315 
317 {
318  int ext_code, ext_len, gce_flags, gce_transparent_index;
319 
320  /* There must be at least 2 bytes:
321  * 1 for extension label and 1 for extension length. */
322  if (bytestream2_get_bytes_left(&s->gb) < 2)
323  return AVERROR_INVALIDDATA;
324 
325  ext_code = bytestream2_get_byteu(&s->gb);
326  ext_len = bytestream2_get_byteu(&s->gb);
327 
328  ff_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
329 
330  switch(ext_code) {
331  case GIF_GCE_EXT_LABEL:
332  if (ext_len != 4)
333  goto discard_ext;
334 
335  /* We need at least 5 bytes more: 4 is for extension body
336  * and 1 for next block size. */
337  if (bytestream2_get_bytes_left(&s->gb) < 5)
338  return AVERROR_INVALIDDATA;
339 
340  gce_flags = bytestream2_get_byteu(&s->gb);
341  bytestream2_skipu(&s->gb, 2); // delay during which the frame is shown
342  gce_transparent_index = bytestream2_get_byteu(&s->gb);
343  if (gce_flags & 0x01)
344  s->transparent_color_index = gce_transparent_index;
345  else
346  s->transparent_color_index = -1;
347  s->gce_disposal = (gce_flags >> 2) & 0x7;
348 
349  ff_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
350  gce_flags,
351  s->transparent_color_index, s->gce_disposal);
352 
353  if (s->gce_disposal > 3) {
354  s->gce_disposal = GCE_DISPOSAL_NONE;
355  ff_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
356  }
357 
358  ext_len = bytestream2_get_byteu(&s->gb);
359  break;
360  }
361 
362  /* NOTE: many extension blocks can come after */
363  discard_ext:
364  while (ext_len) {
365  /* There must be at least ext_len bytes and 1 for next block size byte. */
366  if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
367  return AVERROR_INVALIDDATA;
368 
369  bytestream2_skipu(&s->gb, ext_len);
370  ext_len = bytestream2_get_byteu(&s->gb);
371 
372  ff_dlog(s->avctx, "ext_len1=%d\n", ext_len);
373  }
374  return 0;
375 }
376 
378 {
379  uint8_t sig[6];
380  int v, n;
381  int background_color_index;
382 
383  if (bytestream2_get_bytes_left(&s->gb) < 13)
384  return AVERROR_INVALIDDATA;
385 
386  /* read gif signature */
387  bytestream2_get_bufferu(&s->gb, sig, 6);
388  if (memcmp(sig, gif87a_sig, 6) &&
389  memcmp(sig, gif89a_sig, 6))
390  return AVERROR_INVALIDDATA;
391 
392  /* read screen header */
393  s->transparent_color_index = -1;
394  s->screen_width = bytestream2_get_le16u(&s->gb);
395  s->screen_height = bytestream2_get_le16u(&s->gb);
396 
397  v = bytestream2_get_byteu(&s->gb);
398  s->color_resolution = ((v & 0x70) >> 4) + 1;
399  s->has_global_palette = (v & 0x80);
400  s->bits_per_pixel = (v & 0x07) + 1;
401  background_color_index = bytestream2_get_byteu(&s->gb);
402  n = bytestream2_get_byteu(&s->gb);
403  if (n) {
404  s->avctx->sample_aspect_ratio.num = n + 15;
405  s->avctx->sample_aspect_ratio.den = 64;
406  }
407 
408  ff_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
409  s->screen_width, s->screen_height, s->bits_per_pixel,
410  s->has_global_palette);
411 
412  if (s->has_global_palette) {
413  s->background_color_index = background_color_index;
414  n = 1 << s->bits_per_pixel;
415  if (bytestream2_get_bytes_left(&s->gb) < n * 3)
416  return AVERROR_INVALIDDATA;
417 
418  gif_read_palette(s, s->global_palette, n);
419  s->bg_color = s->global_palette[s->background_color_index];
420  } else
421  s->background_color_index = -1;
422 
423  return 0;
424 }
425 
427 {
428  while (bytestream2_get_bytes_left(&s->gb) > 0) {
429  int code = bytestream2_get_byte(&s->gb);
430  int ret;
431 
432  av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
433 
434  switch (code) {
435  case GIF_IMAGE_SEPARATOR:
436  return gif_read_image(s, frame);
438  if ((ret = gif_read_extension(s)) < 0)
439  return ret;
440  break;
441  case GIF_TRAILER:
442  /* end of image */
443  return AVERROR_EOF;
444  default:
445  /* erroneous block label */
446  return AVERROR_INVALIDDATA;
447  }
448  }
449  return AVERROR_EOF;
450 }
451 
453 {
454  GifState *s = avctx->priv_data;
455 
456  s->avctx = avctx;
457 
458  avctx->pix_fmt = AV_PIX_FMT_RGB32;
459  s->frame = av_frame_alloc();
460  if (!s->frame)
461  return AVERROR(ENOMEM);
462  ff_lzw_decode_open(&s->lzw);
463  if (!s->lzw)
464  return AVERROR(ENOMEM);
465  return 0;
466 }
467 
468 static int gif_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
469  int *got_frame, AVPacket *avpkt)
470 {
471  GifState *s = avctx->priv_data;
472  int ret;
473 
474  bytestream2_init(&s->gb, avpkt->data, avpkt->size);
475 
476  s->frame->pts = avpkt->pts;
477  s->frame->pkt_dts = avpkt->dts;
478  s->frame->pkt_duration = avpkt->duration;
479 
480  if (avpkt->size >= 6) {
481  s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
482  memcmp(avpkt->data, gif89a_sig, 6) == 0;
483  } else {
484  s->keyframe = 0;
485  }
486 
487  if (s->keyframe) {
488  s->keyframe_ok = 0;
489  s->gce_prev_disposal = GCE_DISPOSAL_NONE;
490  if ((ret = gif_read_header1(s)) < 0)
491  return ret;
492 
493  if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
494  return ret;
495 
496  av_frame_unref(s->frame);
497  if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)
498  return ret;
499 
500  av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
501  if (!s->idx_line)
502  return AVERROR(ENOMEM);
503 
504  s->frame->pict_type = AV_PICTURE_TYPE_I;
505  s->frame->key_frame = 1;
506  s->keyframe_ok = 1;
507  } else {
508  if (!s->keyframe_ok) {
509  av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
510  return AVERROR_INVALIDDATA;
511  }
512 
513  if ((ret = ff_reget_buffer(avctx, s->frame, 0)) < 0)
514  return ret;
515 
516  s->frame->pict_type = AV_PICTURE_TYPE_P;
517  s->frame->key_frame = 0;
518  }
519 
520  ret = gif_parse_next_image(s, s->frame);
521  if (ret < 0)
522  return ret;
523 
524  if ((ret = av_frame_ref(rframe, s->frame)) < 0)
525  return ret;
526  *got_frame = 1;
527 
528  return bytestream2_tell(&s->gb);
529 }
530 
532 {
533  GifState *s = avctx->priv_data;
534 
535  ff_lzw_decode_close(&s->lzw);
536  av_frame_free(&s->frame);
537  av_freep(&s->idx_line);
538  av_freep(&s->stored_img);
539 
540  return 0;
541 }
542 
543 static const AVOption options[] = {
544  { "trans_color", "color value (ARGB) that is used instead of transparent color",
545  offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
546  {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
548  { NULL },
549 };
550 
551 static const AVClass decoder_class = {
552  .class_name = "gif decoder",
553  .item_name = av_default_item_name,
554  .option = options,
555  .version = LIBAVUTIL_VERSION_INT,
556  .category = AV_CLASS_CATEGORY_DECODER,
557 };
558 
560  .p.name = "gif",
561  .p.long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
562  .p.type = AVMEDIA_TYPE_VIDEO,
563  .p.id = AV_CODEC_ID_GIF,
564  .priv_data_size = sizeof(GifState),
566  .close = gif_decode_close,
568  .p.capabilities = AV_CODEC_CAP_DR1,
569  .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE |
571  .p.priv_class = &decoder_class,
572 };
GIF_TRANSPARENT_COLOR
#define GIF_TRANSPARENT_COLOR
Definition: gifdec.c:37
AV_LOG_WARNING
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:186
FF_CODEC_CAP_INIT_CLEANUP
#define FF_CODEC_CAP_INIT_CLEANUP
The codec allows calling the close function for deallocation even if the init function returned a fai...
Definition: codec_internal.h:39
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
opt.h
AV_CLASS_CATEGORY_DECODER
@ AV_CLASS_CATEGORY_DECODER
Definition: log.h:35
AV_OPT_FLAG_VIDEO_PARAM
#define AV_OPT_FLAG_VIDEO_PARAM
Definition: opt.h:284
color
Definition: vf_paletteuse.c:600
GetByteContext
Definition: bytestream.h:33
options
static const AVOption options[]
Definition: gifdec.c:543
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:57
GifState::idx_line_size
int idx_line_size
Definition: gifdec.c:53
GifState::background_color_index
int background_color_index
Definition: gifdec.c:47
bytestream2_skipu
static av_always_inline void bytestream2_skipu(GetByteContext *g, unsigned int size)
Definition: bytestream.h:174
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:111
GIF_TRAILER
#define GIF_TRAILER
Definition: gif.h:42
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:325
w
uint8_t w
Definition: llviddspenc.c:38
internal.h
AVPacket::data
uint8_t * data
Definition: packet.h:374
AVOption
AVOption.
Definition: opt.h:251
FFCodec
Definition: codec_internal.h:112
gif_decode_frame
static int gif_decode_frame(AVCodecContext *avctx, AVFrame *rframe, int *got_frame, AVPacket *avpkt)
Definition: gifdec.c:468
AVPacket::duration
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:392
ff_lzw_decode
int ff_lzw_decode(LZWState *p, uint8_t *buf, int len)
Decode given number of bytes NOTE: the algorithm here is inspired from the LZW GIF decoder written by...
Definition: lzw.c:169
GIF_GCE_EXT_LABEL
#define GIF_GCE_EXT_LABEL
Definition: gif.h:45
ff_lzw_decode_close
av_cold void ff_lzw_decode_close(LZWState **p)
Definition: lzw.c:118
AVFrame::data
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:346
init
static int init
Definition: av_tx.c:47
GifState::screen_height
int screen_height
Definition: gifdec.c:43
gif_parse_next_image
static int gif_parse_next_image(GifState *s, AVFrame *frame)
Definition: gifdec.c:426
FFCodec::p
AVCodec p
The public AVCodec.
Definition: codec_internal.h:116
gif_decode_init
static av_cold int gif_decode_init(AVCodecContext *avctx)
Definition: gifdec.c:452
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:99
gif89a_sig
static const uint8_t gif89a_sig[6]
Definition: gif.h:35
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
av_cold
#define av_cold
Definition: attributes.h:90
GifState::stored_bg_color
int stored_bg_color
Definition: gifdec.c:65
GifState::color_resolution
int color_resolution
Definition: gifdec.c:49
width
#define width
FF_CODEC_DECODE_CB
#define FF_CODEC_DECODE_CB(func)
Definition: codec_internal.h:254
s
#define s(width, name)
Definition: cbs_vp9.c:256
ff_lzw_decode_open
av_cold void ff_lzw_decode_open(LZWState **p)
Definition: lzw.c:113
GIF_IMAGE_SEPARATOR
#define GIF_IMAGE_SEPARATOR
Definition: gif.h:44
AV_LOG_DEBUG
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:201
decoder_class
static const AVClass decoder_class
Definition: gifdec.c:551
LZWState
Definition: lzw.c:46
GifState::trans_color
int trans_color
color value that is used instead of transparent color
Definition: gifdec.c:77
pass
#define pass
Definition: fft_template.c:608
GifState::gce_l
int gce_l
Definition: gifdec.c:59
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
NULL
#define NULL
Definition: coverity.c:32
gif_read_extension
static int gif_read_extension(GifState *s)
Definition: gifdec.c:316
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:237
AV_PICTURE_TYPE_I
@ AV_PICTURE_TYPE_I
Intra.
Definition: avutil.h:274
GifState::keyframe_ok
int keyframe_ok
Definition: gifdec.c:76
gif_read_header1
static int gif_read_header1(GifState *s)
Definition: gifdec.c:377
GifState::stored_img_size
int stored_img_size
Definition: gifdec.c:64
FF_LZW_GIF
@ FF_LZW_GIF
Definition: lzw.h:38
bytestream2_get_bytes_left
static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:158
bytestream2_tell
static av_always_inline int bytestream2_tell(GetByteContext *g)
Definition: bytestream.h:192
ff_dlog
#define ff_dlog(a,...)
Definition: tableprint_vlc.h:28
gif_read_image
static int gif_read_image(GifState *s, AVFrame *frame)
Definition: gifdec.c:131
GifState::screen_width
int screen_width
Definition: gifdec.c:42
ff_get_buffer
int ff_get_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
Get a buffer for a frame.
Definition: decode.c:1403
AV_CODEC_CAP_DR1
#define AV_CODEC_CAP_DR1
Codec uses get_buffer() or get_encode_buffer() for allocating buffers and supports custom allocators.
Definition: codec.h:52
AVPacket::size
int size
Definition: packet.h:375
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
av_frame_ref
int av_frame_ref(AVFrame *dst, const AVFrame *src)
Set up a new reference to the data described by the source frame.
Definition: frame.c:343
codec_internal.h
lzw.h
LZW decoding routines.
for
for(k=2;k<=8;++k)
Definition: h264pred_template.c:425
gif_fill_rect
static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
Definition: gifdec.c:97
gif.h
GifState::frame
AVFrame * frame
Definition: gifdec.c:41
GifState::bits_per_pixel
int bits_per_pixel
Definition: gifdec.c:45
GCE_DISPOSAL_NONE
#define GCE_DISPOSAL_NONE
Definition: gif.h:37
GCE_DISPOSAL_RESTORE
#define GCE_DISPOSAL_RESTORE
Definition: gif.h:40
AVPacket::dts
int64_t dts
Decompression timestamp in AVStream->time_base units; the time at which the packet is decompressed.
Definition: packet.h:373
height
#define height
AV_PIX_FMT_RGB32
#define AV_PIX_FMT_RGB32
Definition: pixfmt.h:379
GifState::gce_disposal
int gce_disposal
Definition: gifdec.c:57
GifState::gce_prev_disposal
int gce_prev_disposal
Definition: gifdec.c:56
GifState::stored_img
uint32_t * stored_img
Definition: gifdec.c:63
GifState::gce_h
int gce_h
Definition: gifdec.c:59
GifState::lzw
LZWState * lzw
Definition: gifdec.c:68
AV_CODEC_ID_GIF
@ AV_CODEC_ID_GIF
Definition: codec_id.h:147
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:269
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:367
code
and forward the test the status of outputs and forward it to the corresponding return FFERROR_NOT_READY If the filters stores internally one or a few frame for some it can consider them to be part of the FIFO and delay acknowledging a status change accordingly Example code
Definition: filter_design.txt:178
gif87a_sig
static const uint8_t gif87a_sig[6]
Definition: gif.h:34
ff_lzw_decode_init
int ff_lzw_decode_init(LZWState *p, int csize, const uint8_t *buf, int buf_size, int mode)
Initialize LZW decoder.
Definition: lzw.c:131
GIF_EXTENSION_INTRODUCER
#define GIF_EXTENSION_INTRODUCER
Definition: gif.h:43
AV_OPT_FLAG_DECODING_PARAM
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:282
FF_CODEC_CAP_INIT_THREADSAFE
#define FF_CODEC_CAP_INIT_THREADSAFE
The codec does not modify any global variables in the init function, allowing to call the init functi...
Definition: codec_internal.h:31
GifState::bg_color
uint32_t bg_color
Definition: gifdec.c:46
av_frame_unref
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:477
AVCodec::name
const char * name
Name of the codec implementation.
Definition: codec.h:203
gif_fill
static void gif_fill(AVFrame *picture, uint32_t color)
Definition: gifdec.c:88
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:599
avcodec.h
GifState::idx_line
uint8_t * idx_line
Definition: gifdec.c:52
ff_reget_buffer
int ff_reget_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
Identical in function to ff_get_buffer(), except it reuses the existing buffer if available.
Definition: decode.c:1521
ret
ret
Definition: filter_design.txt:187
GCE_DISPOSAL_BACKGROUND
#define GCE_DISPOSAL_BACKGROUND
Definition: gif.h:39
AVClass::class_name
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:71
frame
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
Definition: filter_design.txt:264
left
Tag MUST be and< 10hcoeff half pel interpolation filter coefficients, hcoeff[0] are the 2 middle coefficients[1] are the next outer ones and so on, resulting in a filter like:...eff[2], hcoeff[1], hcoeff[0], hcoeff[0], hcoeff[1], hcoeff[2] ... the sign of the coefficients is not explicitly stored but alternates after each coeff and coeff[0] is positive, so ...,+,-,+,-,+,+,-,+,-,+,... hcoeff[0] is not explicitly stored but found by subtracting the sum of all stored coefficients with signs from 32 hcoeff[0]=32 - hcoeff[1] - hcoeff[2] - ... a good choice for hcoeff and htaps is htaps=6 hcoeff={40,-10, 2} an alternative which requires more computations at both encoder and decoder side and may or may not be better is htaps=8 hcoeff={42,-14, 6,-2}ref_frames minimum of the number of available reference frames and max_ref_frames for example the first frame after a key frame always has ref_frames=1spatial_decomposition_type wavelet type 0 is a 9/7 symmetric compact integer wavelet 1 is a 5/3 symmetric compact integer wavelet others are reserved stored as delta from last, last is reset to 0 if always_reset||keyframeqlog quality(logarithmic quantizer scale) stored as delta from last, last is reset to 0 if always_reset||keyframemv_scale stored as delta from last, last is reset to 0 if always_reset||keyframe FIXME check that everything works fine if this changes between framesqbias dequantization bias stored as delta from last, last is reset to 0 if always_reset||keyframeblock_max_depth maximum depth of the block tree stored as delta from last, last is reset to 0 if always_reset||keyframequant_table quantization tableHighlevel bitstream structure:==============================--------------------------------------------|Header|--------------------------------------------|------------------------------------|||Block0||||split?||||yes no||||......... intra?||||:Block01 :yes no||||:Block02 :....... ..........||||:Block03 ::y DC ::ref index:||||:Block04 ::cb DC ::motion x :||||......... :cr DC ::motion y :||||....... ..........|||------------------------------------||------------------------------------|||Block1|||...|--------------------------------------------|------------ ------------ ------------|||Y subbands||Cb subbands||Cr subbands||||--- ---||--- ---||--- ---|||||LL0||HL0||||LL0||HL0||||LL0||HL0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||LH0||HH0||||LH0||HH0||||LH0||HH0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HL1||LH1||||HL1||LH1||||HL1||LH1|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HH1||HL2||||HH1||HL2||||HH1||HL2|||||...||...||...|||------------ ------------ ------------|--------------------------------------------Decoding process:=================------------|||Subbands|------------||||------------|Intra DC||||LL0 subband prediction ------------|\ Dequantization ------------------- \||Reference frames|\ IDWT|------- -------|Motion \|||Frame 0||Frame 1||Compensation . OBMC v -------|------- -------|--------------. \------> Frame n output Frame Frame<----------------------------------/|...|------------------- Range Coder:============Binary Range Coder:------------------- The implemented range coder is an adapted version based upon "Range encoding: an algorithm for removing redundancy from a digitised message." by G. N. N. Martin. The symbols encoded by the Snow range coder are bits(0|1). The associated probabilities are not fix but change depending on the symbol mix seen so far. bit seen|new state ---------+----------------------------------------------- 0|256 - state_transition_table[256 - old_state];1|state_transition_table[old_state];state_transition_table={ 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 190, 191, 192, 194, 194, 195, 196, 197, 198, 199, 200, 201, 202, 202, 204, 205, 206, 207, 208, 209, 209, 210, 211, 212, 213, 215, 215, 216, 217, 218, 219, 220, 220, 222, 223, 224, 225, 226, 227, 227, 229, 229, 230, 231, 232, 234, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 248, 0, 0, 0, 0, 0, 0, 0};FIXME Range Coding of integers:------------------------- FIXME Neighboring Blocks:===================left and top are set to the respective blocks unless they are outside of the image in which case they are set to the Null block top-left is set to the top left block unless it is outside of the image in which case it is set to the left block if this block has no larger parent block or it is at the left side of its parent block and the top right block is not outside of the image then the top right block is used for top-right else the top-left block is used Null block y, cb, cr are 128 level, ref, mx and my are 0 Motion Vector Prediction:=========================1. the motion vectors of all the neighboring blocks are scaled to compensate for the difference of reference frames scaled_mv=(mv *(256 *(current_reference+1)/(mv.reference+1))+128)> the median of the scaled left
Definition: snow.txt:386
GifState::keyframe
int keyframe
Definition: gifdec.c:75
GifState::transparent_color_index
int transparent_color_index
Definition: gifdec.c:48
AVCodecContext
main external API structure.
Definition: avcodec.h:389
AVFrame::height
int height
Definition: frame.h:397
GifState::local_palette
uint32_t local_palette[256]
Definition: gifdec.c:72
gif_copy_img_rect
static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst, int linesize, int l, int t, int w, int h)
Definition: gifdec.c:113
GifState
Definition: gifdec.c:39
ff_gif_decoder
const FFCodec ff_gif_decoder
Definition: gifdec.c:559
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
GifState::has_global_palette
int has_global_palette
Definition: gifdec.c:44
gif_read_palette
static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
Definition: gifdec.c:80
AV_PICTURE_TYPE_P
@ AV_PICTURE_TYPE_P
Predicted.
Definition: avutil.h:275
AVMEDIA_TYPE_VIDEO
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
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:90
bytestream2_get_bufferu
static av_always_inline unsigned int bytestream2_get_bufferu(GetByteContext *g, uint8_t *dst, unsigned int size)
Definition: bytestream.h:277
AVPacket
This structure stores compressed data.
Definition: packet.h:351
AVCodecContext::priv_data
void * priv_data
Definition: avcodec.h:416
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:34
av_fast_malloc
void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
Allocate a buffer, reusing the given one if large enough.
Definition: mem.c:561
src
INIT_CLIP pixel * src
Definition: h264pred_template.c:418
GifState::gb
GetByteContext gb
Definition: gifdec.c:67
bytestream.h
imgutils.h
bytestream2_init
static av_always_inline void bytestream2_init(GetByteContext *g, const uint8_t *buf, int buf_size)
Definition: bytestream.h:137
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
gif_decode_close
static av_cold int gif_decode_close(AVCodecContext *avctx)
Definition: gifdec.c:531
AVFrame::linesize
int linesize[AV_NUM_DATA_POINTERS]
For video, a positive or negative value, which is typically indicating the size in bytes of each pict...
Definition: frame.h:370
GifState::gce_w
int gce_w
Definition: gifdec.c:59
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
ff_lzw_decode_tail
int ff_lzw_decode_tail(LZWState *p)
Definition: lzw.c:99
h
h
Definition: vp9dsp_template.c:2038
GifState::gce_t
int gce_t
Definition: gifdec.c:59
GifState::global_palette
uint32_t global_palette[256]
Definition: gifdec.c:71
GifState::avctx
AVCodecContext * avctx
Definition: gifdec.c:74