FFmpeg
sga.c
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1 /*
2  * Copyright (c) 2021 Paul B Mahol
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include "libavutil/common.h"
22 #include "avcodec.h"
23 #include "get_bits.h"
24 #include "bytestream.h"
25 #include "internal.h"
26 
27 #define PALDATA_FOLLOWS_TILEDATA 4
28 #define HAVE_COMPRESSED_TILEMAP 32
29 #define HAVE_TILEMAP 128
30 
31 typedef struct SGAVideoContext {
33 
43 
44  int flags;
45  int nb_pal;
46  int nb_tiles;
48  int shift;
49  int plus;
50  int swap;
51 
52  uint32_t pal[256];
53  uint8_t *tileindex_data;
54  unsigned tileindex_size;
55  uint8_t *palmapindex_data;
56  unsigned palmapindex_size;
57  uint8_t uncompressed[65536];
59 
61 {
62  avctx->pix_fmt = AV_PIX_FMT_PAL8;
63  return 0;
64 }
65 
66 static int decode_palette(GetByteContext *gb, uint32_t *pal)
67 {
68  GetBitContext gbit;
69 
70  if (bytestream2_get_bytes_left(gb) < 18)
71  return AVERROR_INVALIDDATA;
72 
73  memset(pal, 0, 16 * sizeof(*pal));
74  init_get_bits8(&gbit, gb->buffer, 18);
75 
76  for (int RGBIndex = 0; RGBIndex < 3; RGBIndex++) {
77  for (int index = 0; index < 16; index++) {
78  unsigned color = get_bits1(&gbit) << RGBIndex;
79  pal[15 - index] |= color << (5 + 16);
80  }
81  }
82 
83  for (int RGBIndex = 0; RGBIndex < 3; RGBIndex++) {
84  for (int index = 0; index < 16; index++) {
85  unsigned color = get_bits1(&gbit) << RGBIndex;
86  pal[15 - index] |= color << (5 + 8);
87  }
88  }
89 
90  for (int RGBIndex = 0; RGBIndex < 3; RGBIndex++) {
91  for (int index = 0; index < 16; index++) {
92  unsigned color = get_bits1(&gbit) << RGBIndex;
93  pal[15 - index] |= color << (5 + 0);
94  }
95  }
96 
97  for (int index = 0; index < 16; index++)
98  pal[index] = (0xFFU << 24) | pal[index] | (pal[index] >> 3);
99 
100  bytestream2_skip(gb, 18);
101 
102  return 0;
103 }
104 
106 {
107  const uint8_t *tt = s->tileindex_data;
108 
109  for (int y = 0; y < s->tiles_h; y++) {
110  for (int x = 0; x < s->tiles_w; x++) {
111  int pal_idx = s->palmapindex_data[y * s->tiles_w + x] * 16;
112  uint8_t *dst = frame->data[0] + y * 8 * frame->linesize[0] + x * 8;
113 
114  for (int yy = 0; yy < 8; yy++) {
115  for (int xx = 0; xx < 8; xx++)
116  dst[xx] = pal_idx + tt[xx];
117  tt += 8;
118 
119  dst += frame->linesize[0];
120  }
121  }
122  }
123 
124  return 0;
125 }
126 
128 {
129  GetByteContext *gb = &s->gb;
130  GetBitContext pm;
131 
132  bytestream2_seek(gb, s->tilemapdata_offset, SEEK_SET);
133  if (bytestream2_get_bytes_left(gb) < s->tilemapdata_size)
134  return AVERROR_INVALIDDATA;
135 
136  init_get_bits8(&pm, gb->buffer, s->tilemapdata_size);
137 
138  for (int y = 0; y < s->tiles_h; y++) {
139  for (int x = 0; x < s->tiles_w; x++) {
140  uint8_t tile[64];
141  int tilemap = get_bits(&pm, 16);
142  int flip_x = (tilemap >> 11) & 1;
143  int flip_y = (tilemap >> 12) & 1;
144  int tindex = av_clip((tilemap & 511) - 1, 0, s->nb_tiles - 1);
145  const uint8_t *tt = s->tileindex_data + tindex * 64;
146  int pal_idx = ((tilemap >> 13) & 3) * 16;
147  uint8_t *dst = frame->data[0] + y * 8 * frame->linesize[0] + x * 8;
148 
149  if (!flip_x && !flip_y) {
150  memcpy(tile, tt, 64);
151  } else if (flip_x && flip_y) {
152  for (int i = 0; i < 8; i++) {
153  for (int j = 0; j < 8; j++)
154  tile[i * 8 + j] = tt[(7 - i) * 8 + 7 - j];
155  }
156  } else if (flip_x) {
157  for (int i = 0; i < 8; i++) {
158  for (int j = 0; j < 8; j++)
159  tile[i * 8 + j] = tt[i * 8 + 7 - j];
160  }
161  } else {
162  for (int i = 0; i < 8; i++) {
163  for (int j = 0; j < 8; j++)
164  tile[i * 8 + j] = tt[(7 - i) * 8 + j];
165  }
166  }
167 
168  for (int yy = 0; yy < 8; yy++) {
169  for (int xx = 0; xx < 8; xx++)
170  dst[xx] = pal_idx + tile[xx + yy * 8];
171 
172  dst += frame->linesize[0];
173  }
174  }
175  }
176 
177  return 0;
178 }
179 
181 {
182  const uint8_t *src = s->tileindex_data;
183  uint8_t *dst = frame->data[0];
184 
185  for (int y = 0; y < frame->height; y += 8) {
186  for (int x = 0; x < frame->width; x += 8) {
187  for (int yy = 0; yy < 8; yy++) {
188  for (int xx = 0; xx < 8; xx++)
189  dst[x + xx + yy * frame->linesize[0]] = src[xx];
190  src += 8;
191  }
192  }
193 
194  dst += 8 * frame->linesize[0];
195  }
196 
197  return 0;
198 }
199 
200 static int lzss_decompress(AVCodecContext *avctx,
201  GetByteContext *gb, uint8_t *dst,
202  int dst_size, int shift, int plus)
203 {
204  int oi = 0;
205 
206  while (bytestream2_get_bytes_left(gb) > 0 && oi < dst_size) {
207  uint16_t displace, header = bytestream2_get_be16(gb);
208  int count, offset;
209 
210  for (int i = 0; i < 16; i++) {
211  switch (header >> 15) {
212  case 0:
213  if (oi + 2 < dst_size) {
214  dst[oi++] = bytestream2_get_byte(gb);
215  dst[oi++] = bytestream2_get_byte(gb);
216  }
217  break;
218  case 1:
219  displace = bytestream2_get_be16(gb);
220  count = displace >> shift;
221  offset = displace & ((1 << shift) - 1);
222 
223  if (displace == 0) {
224  while (bytestream2_get_bytes_left(gb) > 0 &&
225  oi < dst_size)
226  dst[oi++] = bytestream2_get_byte(gb);
227  return oi;
228  }
229 
230  count += plus;
231 
232  if (offset <= 0)
233  offset = 1;
234  if (oi < offset || oi + count * 2 > dst_size)
235  return AVERROR_INVALIDDATA;
236  for (int j = 0; j < count * 2; j++) {
237  dst[oi] = dst[oi - offset];
238  oi++;
239  }
240  break;
241  }
242 
243  header <<= 1;
244  }
245  }
246 
247  return AVERROR_INVALIDDATA;
248 }
249 
251 {
252  SGAVideoContext *s = avctx->priv_data;
253  const int bits = (s->nb_pal + 1) / 2;
254  GetByteContext *gb = &s->gb;
255  GetBitContext pm;
256 
257  bytestream2_seek(gb, s->palmapdata_offset, SEEK_SET);
258  if (bytestream2_get_bytes_left(gb) < s->palmapdata_size)
259  return AVERROR_INVALIDDATA;
260  init_get_bits8(&pm, gb->buffer, s->palmapdata_size);
261 
262  for (int y = 0; y < s->tiles_h; y++) {
263  uint8_t *dst = s->palmapindex_data + y * s->tiles_w;
264 
265  for (int x = 0; x < s->tiles_w; x++)
266  dst[x] = get_bits(&pm, bits);
267 
268  dst += s->tiles_w;
269  }
270 
271  return 0;
272 }
273 
274 static int decode_tiledata(AVCodecContext *avctx)
275 {
276  SGAVideoContext *s = avctx->priv_data;
277  GetByteContext *gb = &s->gb;
278  GetBitContext tm;
279 
280  bytestream2_seek(gb, s->tiledata_offset, SEEK_SET);
281  if (bytestream2_get_bytes_left(gb) < s->tiledata_size)
282  return AVERROR_INVALIDDATA;
283  init_get_bits8(&tm, gb->buffer, s->tiledata_size);
284 
285  for (int n = 0; n < s->nb_tiles; n++) {
286  uint8_t *dst = s->tileindex_data + n * 64;
287 
288  for (int yy = 0; yy < 8; yy++) {
289  for (int xx = 0; xx < 8; xx++)
290  dst[xx] = get_bits(&tm, 4);
291 
292  dst += 8;
293  }
294  }
295 
296  for (int i = 0; i < s->nb_tiles && s->swap; i++) {
297  uint8_t *dst = s->tileindex_data + i * 64;
298 
299  for (int j = 8; j < 64; j += 16) {
300  for (int k = 0; k < 8; k += 2)
301  FFSWAP(uint8_t, dst[j + k], dst[j+k+1]);
302  }
303  }
304 
305  return 0;
306 }
307 
308 static int sga_decode_frame(AVCodecContext *avctx, void *data,
309  int *got_frame, AVPacket *avpkt)
310 {
311  SGAVideoContext *s = avctx->priv_data;
312  GetByteContext *gb = &s->gb;
313  AVFrame *frame = data;
314  int ret, type;
315 
316  if (avpkt->size <= 14)
317  return AVERROR_INVALIDDATA;
318 
319  s->flags = avpkt->data[8];
320  s->nb_pal = avpkt->data[9];
321  s->tiles_w = avpkt->data[10];
322  s->tiles_h = avpkt->data[11];
323 
324  if (s->nb_pal > 4)
325  return AVERROR_INVALIDDATA;
326 
327  if ((ret = ff_set_dimensions(avctx,
328  s->tiles_w * 8,
329  s->tiles_h * 8)) < 0)
330  return ret;
331 
332  av_fast_padded_malloc(&s->tileindex_data, &s->tileindex_size,
333  avctx->width * avctx->height);
334  if (!s->tileindex_data)
335  return AVERROR(ENOMEM);
336 
337  av_fast_padded_malloc(&s->palmapindex_data, &s->palmapindex_size,
338  s->tiles_w * s->tiles_h);
339  if (!s->palmapindex_data)
340  return AVERROR(ENOMEM);
341 
342  if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
343  return ret;
344 
345  bytestream2_init(gb, avpkt->data, avpkt->size);
346 
347  type = bytestream2_get_byte(gb);
348  s->metadata_size = 12 + ((!!(s->flags & HAVE_TILEMAP)) * 2);
349  s->nb_tiles = s->flags & HAVE_TILEMAP ? AV_RB16(avpkt->data + 12) : s->tiles_w * s->tiles_h;
350  if (s->nb_tiles > s->tiles_w * s->tiles_h)
351  return AVERROR_INVALIDDATA;
352 
353  av_log(avctx, AV_LOG_DEBUG, "type: %X flags: %X nb_tiles: %d\n", type, s->flags, s->nb_tiles);
354 
355  switch (type) {
356  case 0xE7:
357  case 0xCB:
358  case 0xCD:
359  s->swap = 1;
360  s->shift = 12;
361  s->plus = 1;
362  break;
363  case 0xC9:
364  s->swap = 1;
365  s->shift = 13;
366  s->plus = 1;
367  break;
368  case 0xC8:
369  s->swap = 1;
370  s->shift = 13;
371  s->plus = 0;
372  break;
373  case 0xC7:
374  s->swap = 0;
375  s->shift = 13;
376  s->plus = 1;
377  break;
378  case 0xC6:
379  s->swap = 0;
380  s->shift = 13;
381  s->plus = 0;
382  break;
383  }
384 
385  if (type == 0xE7) {
386  int offset = s->metadata_size, left;
387  int sizes[3];
388 
389  bytestream2_seek(gb, s->metadata_size, SEEK_SET);
390 
391  for (int i = 0; i < 3; i++)
392  sizes[i] = bytestream2_get_be16(gb);
393 
394  for (int i = 0; i < 3; i++) {
395  int size = sizes[i];
396  int raw = size >> 15;
397 
398  size &= (1 << 15) - 1;
399 
400  if (raw) {
402  return AVERROR_INVALIDDATA;
403 
404  if (sizeof(s->uncompressed) - offset < size)
405  return AVERROR_INVALIDDATA;
406 
407  memcpy(s->uncompressed + offset, gb->buffer, size);
408  bytestream2_skip(gb, size);
409  } else {
410  GetByteContext gb2;
411 
413  return AVERROR_INVALIDDATA;
414 
415  bytestream2_init(&gb2, gb->buffer, size);
416  ret = lzss_decompress(avctx, &gb2, s->uncompressed + offset,
417  sizeof(s->uncompressed) - offset, s->shift, s->plus);
418  if (ret < 0)
419  return ret;
420  bytestream2_skip(gb, size);
421  size = ret;
422  }
423 
424  offset += size;
425  }
426 
428  if (sizeof(s->uncompressed) - offset < left)
429  return AVERROR_INVALIDDATA;
430 
431  bytestream2_get_buffer(gb, s->uncompressed + offset, left);
432 
433  offset += left;
434  bytestream2_init(gb, s->uncompressed, offset);
435  }
436 
437  switch (type) {
438  case 0xCD:
439  case 0xCB:
440  case 0xC9:
441  case 0xC8:
442  case 0xC7:
443  case 0xC6:
444  bytestream2_seek(gb, s->metadata_size, SEEK_SET);
445  ret = lzss_decompress(avctx, gb, s->uncompressed + s->metadata_size,
446  sizeof(s->uncompressed) - s->metadata_size, s->shift, s->plus);
447  if (ret < 0)
448  return ret;
449  bytestream2_init(gb, s->uncompressed, ret + s->metadata_size);
450  case 0xE7:
451  case 0xC1:
452  s->tiledata_size = s->nb_tiles * 32;
453  s->paldata_size = s->nb_pal * 18;
454  s->tiledata_offset = s->flags & PALDATA_FOLLOWS_TILEDATA ? s->metadata_size : s->metadata_size + s->paldata_size;
455  s->paldata_offset = s->flags & PALDATA_FOLLOWS_TILEDATA ? s->metadata_size + s->tiledata_size : s->metadata_size;
456  s->palmapdata_offset = (s->flags & HAVE_TILEMAP) ? -1 : s->paldata_offset + s->paldata_size;
457  s->palmapdata_size = (s->flags & HAVE_TILEMAP) || s->nb_pal < 2 ? 0 : (s->tiles_w * s->tiles_h * ((s->nb_pal + 1) / 2) + 7) / 8;
458  s->tilemapdata_size = (s->flags & HAVE_TILEMAP) ? s->tiles_w * s->tiles_h * 2 : 0;
459  s->tilemapdata_offset = (s->flags & HAVE_TILEMAP) ? s->paldata_offset + s->paldata_size: -1;
460 
461  bytestream2_seek(gb, s->paldata_offset, SEEK_SET);
462  for (int n = 0; n < s->nb_pal; n++) {
463  ret = decode_palette(gb, s->pal + 16 * n);
464  if (ret < 0)
465  return ret;
466  }
467 
468  if (s->tiledata_size > 0) {
469  ret = decode_tiledata(avctx);
470  if (ret < 0)
471  return ret;
472  }
473 
474  if (s->palmapdata_size > 0) {
475  ret = decode_palmapdata(avctx);
476  if (ret < 0)
477  return ret;
478  }
479 
480  if (s->palmapdata_size > 0 && s->tiledata_size > 0) {
482  if (ret < 0)
483  return ret;
484  } else if (s->tilemapdata_size > 0 && s->tiledata_size > 0) {
486  if (ret < 0)
487  return ret;
488  } else if (s->tiledata_size > 0) {
489  ret = decode_index(s, frame);
490  if (ret < 0)
491  return ret;
492  }
493  break;
494  default:
495  av_log(avctx, AV_LOG_ERROR, "Unknown type: %X\n", type);
496  return AVERROR_INVALIDDATA;
497  }
498 
499  memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);
500  frame->palette_has_changed = 1;
501  frame->pict_type = AV_PICTURE_TYPE_I;
502  frame->key_frame = 1;
503 
504  *got_frame = 1;
505 
506  return avpkt->size;
507 }
508 
510 {
511  SGAVideoContext *s = avctx->priv_data;
512 
513  av_freep(&s->tileindex_data);
514  s->tileindex_size = 0;
515 
516  av_freep(&s->palmapindex_data);
517  s->palmapindex_size = 0;
518 
519  return 0;
520 }
521 
523  .name = "sga",
524  .long_name = NULL_IF_CONFIG_SMALL("Digital Pictures SGA Video"),
525  .type = AVMEDIA_TYPE_VIDEO,
526  .id = AV_CODEC_ID_SGA_VIDEO,
527  .priv_data_size = sizeof(SGAVideoContext),
530  .close = sga_decode_end,
531  .capabilities = AV_CODEC_CAP_DR1,
532  .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
533 };
AVCodec
AVCodec.
Definition: codec.h:202
SGAVideoContext::tileindex_data
uint8_t * tileindex_data
Definition: sga.c:53
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: internal.h:42
av_clip
#define av_clip
Definition: common.h:96
init
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:31
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
SGAVideoContext::palmapindex_size
unsigned palmapindex_size
Definition: sga.c:56
color
Definition: vf_paletteuse.c:587
GetByteContext
Definition: bytestream.h:33
SGAVideoContext::pal
uint32_t pal[256]
Definition: sga.c:52
SGAVideoContext::nb_tiles
int nb_tiles
Definition: sga.c:46
bytestream2_seek
static av_always_inline int bytestream2_seek(GetByteContext *g, int offset, int whence)
Definition: bytestream.h:212
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:303
index
fg index
Definition: ffmpeg_filter.c:168
internal.h
AVPacket::data
uint8_t * data
Definition: packet.h:373
data
const char data[16]
Definition: mxf.c:143
SGAVideoContext::tiles_w
int tiles_w
Definition: sga.c:47
SGAVideoContext::plus
int plus
Definition: sga.c:49
SGAVideoContext::tiledata_offset
int tiledata_offset
Definition: sga.c:36
lzss_decompress
static int lzss_decompress(AVCodecContext *avctx, GetByteContext *gb, uint8_t *dst, int dst_size, int shift, int plus)
Definition: sga.c:200
SGAVideoContext::tileindex_size
unsigned tileindex_size
Definition: sga.c:54
bytestream2_skip
static av_always_inline void bytestream2_skip(GetByteContext *g, unsigned int size)
Definition: bytestream.h:168
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:380
SGAVideoContext::metadata_size
int metadata_size
Definition: sga.c:34
GetBitContext
Definition: get_bits.h:62
sga_decode_frame
static int sga_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
Definition: sga.c:308
type
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf type
Definition: writing_filters.txt:86
SGAVideoContext::tiledata_size
int tiledata_size
Definition: sga.c:35
sga_decode_end
static av_cold int sga_decode_end(AVCodecContext *avctx)
Definition: sga.c:509
HAVE_TILEMAP
#define HAVE_TILEMAP
Definition: sga.c:29
decode_palmapdata
static int decode_palmapdata(AVCodecContext *avctx)
Definition: sga.c:250
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
decode_tiledata
static int decode_tiledata(AVCodecContext *avctx)
Definition: sga.c:274
av_cold
#define av_cold
Definition: attributes.h:90
init_get_bits8
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:678
SGAVideoContext::gb
GetByteContext gb
Definition: sga.c:32
decode
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, FILE *outfile)
Definition: decode_audio.c:71
s
#define s(width, name)
Definition: cbs_vp9.c:257
AV_CODEC_ID_SGA_VIDEO
@ AV_CODEC_ID_SGA_VIDEO
Definition: codec_id.h:309
GetByteContext::buffer
const uint8_t * buffer
Definition: bytestream.h:34
bits
uint8_t bits
Definition: vp3data.h:141
decode_index
static int decode_index(SGAVideoContext *s, AVFrame *frame)
Definition: sga.c:180
AV_LOG_DEBUG
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:201
get_bits.h
sizes
static const int sizes[][2]
Definition: img2dec.c:53
AVPALETTE_SIZE
#define AVPALETTE_SIZE
Definition: pixfmt.h:32
AV_PICTURE_TYPE_I
@ AV_PICTURE_TYPE_I
Intra.
Definition: avutil.h:274
get_bits1
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:499
src
#define src
Definition: vp8dsp.c:255
bytestream2_get_buffer
static av_always_inline unsigned int bytestream2_get_buffer(GetByteContext *g, uint8_t *dst, unsigned int size)
Definition: bytestream.h:267
SGAVideoContext::nb_pal
int nb_pal
Definition: sga.c:45
SGAVideoContext::palmapindex_data
uint8_t * palmapindex_data
Definition: sga.c:55
decode_palette
static int decode_palette(GetByteContext *gb, uint32_t *pal)
Definition: sga.c:66
bytestream2_get_bytes_left
static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:158
ff_get_buffer
int ff_get_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
Get a buffer for a frame.
Definition: decode.c:1652
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:374
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
size
int size
Definition: twinvq_data.h:10344
header
static const uint8_t header[24]
Definition: sdr2.c:67
SGAVideoContext::flags
int flags
Definition: sga.c:44
offset
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset
Definition: writing_filters.txt:86
PALDATA_FOLLOWS_TILEDATA
#define PALDATA_FOLLOWS_TILEDATA
Definition: sga.c:27
SGAVideoContext
Definition: sga.c:31
decode_index_palmap
static int decode_index_palmap(SGAVideoContext *s, AVFrame *frame)
Definition: sga.c:105
SGAVideoContext::tilemapdata_offset
int tilemapdata_offset
Definition: sga.c:38
SGAVideoContext::tilemapdata_size
int tilemapdata_size
Definition: sga.c:37
i
int i
Definition: input.c:406
SGAVideoContext::palmapdata_size
int palmapdata_size
Definition: sga.c:42
SGAVideoContext::swap
int swap
Definition: sga.c:50
common.h
decode_index_tilemap
static int decode_index_tilemap(SGAVideoContext *s, AVFrame *frame)
Definition: sga.c:127
av_fast_padded_malloc
void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size)
Same behaviour av_fast_malloc but the buffer has additional AV_INPUT_BUFFER_PADDING_SIZE at the end w...
Definition: utils.c:50
AVCodec::name
const char * name
Name of the codec implementation.
Definition: codec.h:209
AVCodecContext::height
int height
Definition: avcodec.h:556
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:593
avcodec.h
SGAVideoContext::shift
int shift
Definition: sga.c:48
AV_PIX_FMT_PAL8
@ AV_PIX_FMT_PAL8
8 bits with AV_PIX_FMT_RGB32 palette
Definition: pixfmt.h:77
ret
ret
Definition: filter_design.txt:187
FFSWAP
#define FFSWAP(type, a, b)
Definition: macros.h:52
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
SGAVideoContext::palmapdata_offset
int palmapdata_offset
Definition: sga.c:41
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
AVCodecContext
main external API structure.
Definition: avcodec.h:383
SGAVideoContext::paldata_size
int paldata_size
Definition: sga.c:39
shift
static int shift(int a, int b)
Definition: sonic.c:83
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:86
ff_sga_decoder
const AVCodec ff_sga_decoder
Definition: sga.c:522
AVPacket
This structure stores compressed data.
Definition: packet.h:350
AVCodecContext::priv_data
void * priv_data
Definition: avcodec.h:410
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:35
AVCodecContext::width
int width
picture width / height.
Definition: avcodec.h:556
bytestream.h
bytestream2_init
static av_always_inline void bytestream2_init(GetByteContext *g, const uint8_t *buf, int buf_size)
Definition: bytestream.h:137
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
SGAVideoContext::tiles_h
int tiles_h
Definition: sga.c:47
sga_decode_init
static av_cold int sga_decode_init(AVCodecContext *avctx)
Definition: sga.c:60
SGAVideoContext::uncompressed
uint8_t uncompressed[65536]
Definition: sga.c:57
AV_RB16
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:98
SGAVideoContext::paldata_offset
int paldata_offset
Definition: sga.c:40