summaryrefslogtreecommitdiff
path: root/libavcodec/xan.c
blob: 662386af9a53fb2d394650cbf5445a6fc3710ef3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
/*
 * Wing Commander/Xan Video Decoder
 * Copyright (c) 2003 The FFmpeg Project
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * Xan video decoder for Wing Commander III computer game
 * by Mario Brito (mbrito@student.dei.uc.pt)
 * and Mike Melanson (melanson@pcisys.net)
 *
 * The xan_wc3 decoder outputs PAL8 data.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "avcodec.h"
#include "bytestream.h"
#define BITSTREAM_READER_LE
#include "get_bits.h"
#include "internal.h"

#define RUNTIME_GAMMA 0

#define VGA__TAG MKTAG('V', 'G', 'A', ' ')
#define PALT_TAG MKTAG('P', 'A', 'L', 'T')
#define SHOT_TAG MKTAG('S', 'H', 'O', 'T')
#define PALETTE_COUNT 256
#define PALETTE_SIZE (PALETTE_COUNT * 3)
#define PALETTES_MAX 256

typedef struct XanContext {

    AVCodecContext *avctx;
    AVFrame *last_frame;

    const uint8_t *buf;
    int size;

    /* scratch space */
    uint8_t *buffer1;
    int buffer1_size;
    uint8_t *buffer2;
    int buffer2_size;

    unsigned *palettes;
    int palettes_count;
    int cur_palette;

    int frame_size;

} XanContext;

static av_cold int xan_decode_end(AVCodecContext *avctx)
{
    XanContext *s = avctx->priv_data;

    av_frame_free(&s->last_frame);

    av_freep(&s->buffer1);
    av_freep(&s->buffer2);
    av_freep(&s->palettes);

    return 0;
}

static av_cold int xan_decode_init(AVCodecContext *avctx)
{
    XanContext *s = avctx->priv_data;

    s->avctx = avctx;
    s->frame_size = 0;

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    s->buffer1_size = avctx->width * avctx->height;
    s->buffer1 = av_malloc(s->buffer1_size);
    if (!s->buffer1)
        return AVERROR(ENOMEM);
    s->buffer2_size = avctx->width * avctx->height;
    s->buffer2 = av_malloc(s->buffer2_size + 130);
    if (!s->buffer2) {
        av_freep(&s->buffer1);
        return AVERROR(ENOMEM);
    }

    s->last_frame = av_frame_alloc();
    if (!s->last_frame) {
        xan_decode_end(avctx);
        return AVERROR(ENOMEM);
    }

    return 0;
}

static int xan_huffman_decode(uint8_t *dest, int dest_len,
                              const uint8_t *src, int src_len)
{
    uint8_t byte = *src++;
    uint8_t ival = byte + 0x16;
    const uint8_t * ptr = src + byte*2;
    int ptr_len = src_len - 1 - byte*2;
    uint8_t val = ival;
    uint8_t *dest_end = dest + dest_len;
    uint8_t *dest_start = dest;
    int ret;
    GetBitContext gb;

    if ((ret = init_get_bits8(&gb, ptr, ptr_len)) < 0)
        return ret;

    while (val != 0x16) {
        unsigned idx = val - 0x17 + get_bits1(&gb) * byte;
        if (idx >= 2 * byte)
            return AVERROR_INVALIDDATA;
        val = src[idx];

        if (val < 0x16) {
            if (dest >= dest_end)
                return dest_len;
            *dest++ = val;
            val = ival;
        }
    }

    return dest - dest_start;
}

/**
 * unpack simple compression
 *
 * @param dest destination buffer of dest_len, must be padded with at least 130 bytes
 */
static void xan_unpack(uint8_t *dest, int dest_len,
                       const uint8_t *src, int src_len)
{
    uint8_t opcode;
    int size;
    uint8_t *dest_org = dest;
    uint8_t *dest_end = dest + dest_len;
    GetByteContext ctx;

    bytestream2_init(&ctx, src, src_len);
    while (dest < dest_end && bytestream2_get_bytes_left(&ctx)) {
        opcode = bytestream2_get_byte(&ctx);

        if (opcode < 0xe0) {
            int size2, back;
            if ((opcode & 0x80) == 0) {
                size = opcode & 3;

                back  = ((opcode & 0x60) << 3) + bytestream2_get_byte(&ctx) + 1;
                size2 = ((opcode & 0x1c) >> 2) + 3;
            } else if ((opcode & 0x40) == 0) {
                size = bytestream2_peek_byte(&ctx) >> 6;

                back  = (bytestream2_get_be16(&ctx) & 0x3fff) + 1;
                size2 = (opcode & 0x3f) + 4;
            } else {
                size = opcode & 3;

                back  = ((opcode & 0x10) << 12) + bytestream2_get_be16(&ctx) + 1;
                size2 = ((opcode & 0x0c) <<  6) + bytestream2_get_byte(&ctx) + 5;
            }

            if (dest_end - dest < size + size2 ||
                dest + size - dest_org < back ||
                bytestream2_get_bytes_left(&ctx) < size)
                return;
            bytestream2_get_buffer(&ctx, dest, size);
            dest += size;
            av_memcpy_backptr(dest, back, size2);
            dest += size2;
        } else {
            int finish = opcode >= 0xfc;
            size = finish ? opcode & 3 : ((opcode & 0x1f) << 2) + 4;

            if (dest_end - dest < size || bytestream2_get_bytes_left(&ctx) < size)
                return;
            bytestream2_get_buffer(&ctx, dest, size);
            dest += size;
            if (finish)
                return;
        }
    }
}

static inline void xan_wc3_output_pixel_run(XanContext *s, AVFrame *frame,
    const uint8_t *pixel_buffer, int x, int y, int pixel_count)
{
    int stride;
    int line_inc;
    int index;
    int current_x;
    int width = s->avctx->width;
    uint8_t *palette_plane;

    palette_plane = frame->data[0];
    stride = frame->linesize[0];
    line_inc = stride - width;
    index = y * stride + x;
    current_x = x;
    while (pixel_count && index < s->frame_size) {
        int count = FFMIN(pixel_count, width - current_x);
        memcpy(palette_plane + index, pixel_buffer, count);
        pixel_count  -= count;
        index        += count;
        pixel_buffer += count;
        current_x    += count;

        if (current_x >= width) {
            index += line_inc;
            current_x = 0;
        }
    }
}

static inline void xan_wc3_copy_pixel_run(XanContext *s, AVFrame *frame,
                                          int x, int y,
                                          int pixel_count, int motion_x,
                                          int motion_y)
{
    int stride;
    int line_inc;
    int curframe_index, prevframe_index;
    int curframe_x, prevframe_x;
    int width = s->avctx->width;
    uint8_t *palette_plane, *prev_palette_plane;

    if (y + motion_y < 0 || y + motion_y >= s->avctx->height ||
        x + motion_x < 0 || x + motion_x >= s->avctx->width)
        return;

    palette_plane = frame->data[0];
    prev_palette_plane = s->last_frame->data[0];
    if (!prev_palette_plane)
        prev_palette_plane = palette_plane;
    stride = frame->linesize[0];
    line_inc = stride - width;
    curframe_index = y * stride + x;
    curframe_x = x;
    prevframe_index = (y + motion_y) * stride + x + motion_x;
    prevframe_x = x + motion_x;

    if (prev_palette_plane == palette_plane && FFABS(curframe_index - prevframe_index) < pixel_count) {
         avpriv_request_sample(s->avctx, "Overlapping copy");
         return ;
    }

    while (pixel_count &&
           curframe_index  < s->frame_size &&
           prevframe_index < s->frame_size) {
        int count = FFMIN3(pixel_count, width - curframe_x,
                           width - prevframe_x);

        memcpy(palette_plane + curframe_index,
               prev_palette_plane + prevframe_index, count);
        pixel_count     -= count;
        curframe_index  += count;
        prevframe_index += count;
        curframe_x      += count;
        prevframe_x     += count;

        if (curframe_x >= width) {
            curframe_index += line_inc;
            curframe_x = 0;
        }

        if (prevframe_x >= width) {
            prevframe_index += line_inc;
            prevframe_x = 0;
        }
    }
}

static int xan_wc3_decode_frame(XanContext *s, AVFrame *frame)
{

    int width  = s->avctx->width;
    int height = s->avctx->height;
    int total_pixels = width * height;
    uint8_t opcode;
    uint8_t flag = 0;
    int size = 0;
    int motion_x, motion_y;
    int x, y, ret;

    uint8_t *opcode_buffer = s->buffer1;
    uint8_t *opcode_buffer_end = s->buffer1 + s->buffer1_size;
    int opcode_buffer_size = s->buffer1_size;
    const uint8_t *imagedata_buffer = s->buffer2;

    /* pointers to segments inside the compressed chunk */
    const uint8_t *huffman_segment;
    GetByteContext       size_segment;
    GetByteContext       vector_segment;
    const uint8_t *imagedata_segment;
    int huffman_offset, size_offset, vector_offset, imagedata_offset,
        imagedata_size;

    if (s->size < 8)
        return AVERROR_INVALIDDATA;

    huffman_offset    = AV_RL16(&s->buf[0]);
    size_offset       = AV_RL16(&s->buf[2]);
    vector_offset     = AV_RL16(&s->buf[4]);
    imagedata_offset  = AV_RL16(&s->buf[6]);

    if (huffman_offset   >= s->size ||
        size_offset      >= s->size ||
        vector_offset    >= s->size ||
        imagedata_offset >= s->size)
        return AVERROR_INVALIDDATA;

    huffman_segment   = s->buf + huffman_offset;
    bytestream2_init(&size_segment,   s->buf + size_offset,   s->size - size_offset);
    bytestream2_init(&vector_segment, s->buf + vector_offset, s->size - vector_offset);
    imagedata_segment = s->buf + imagedata_offset;

    if ((ret = xan_huffman_decode(opcode_buffer, opcode_buffer_size,
                                  huffman_segment, s->size - huffman_offset)) < 0)
        return AVERROR_INVALIDDATA;
    opcode_buffer_end = opcode_buffer + ret;

    if (imagedata_segment[0] == 2) {
        xan_unpack(s->buffer2, s->buffer2_size,
                   &imagedata_segment[1], s->size - imagedata_offset - 1);
        imagedata_size = s->buffer2_size;
    } else {
        imagedata_size = s->size - imagedata_offset - 1;
        imagedata_buffer = &imagedata_segment[1];
    }

    /* use the decoded data segments to build the frame */
    x = y = 0;
    while (total_pixels && opcode_buffer < opcode_buffer_end) {

        opcode = *opcode_buffer++;
        size = 0;

        switch (opcode) {

        case 0:
            flag ^= 1;
            continue;

        case 1:
        case 2:
        case 3:
        case 4:
        case 5:
        case 6:
        case 7:
        case 8:
            size = opcode;
            break;

        case 12:
        case 13:
        case 14:
        case 15:
        case 16:
        case 17:
        case 18:
            size += (opcode - 10);
            break;

        case 9:
        case 19:
            if (bytestream2_get_bytes_left(&size_segment) < 1) {
                av_log(s->avctx, AV_LOG_ERROR, "size_segment overread\n");
                return AVERROR_INVALIDDATA;
            }
            size = bytestream2_get_byte(&size_segment);
            break;

        case 10:
        case 20:
            if (bytestream2_get_bytes_left(&size_segment) < 2) {
                av_log(s->avctx, AV_LOG_ERROR, "size_segment overread\n");
                return AVERROR_INVALIDDATA;
            }
            size = bytestream2_get_be16(&size_segment);
            break;

        case 11:
        case 21:
            if (bytestream2_get_bytes_left(&size_segment) < 3) {
                av_log(s->avctx, AV_LOG_ERROR, "size_segment overread\n");
                return AVERROR_INVALIDDATA;
            }
            size = bytestream2_get_be24(&size_segment);
            break;
        }

        if (size > total_pixels)
            break;

        if (opcode < 12) {
            flag ^= 1;
            if (flag) {
                /* run of (size) pixels is unchanged from last frame */
                xan_wc3_copy_pixel_run(s, frame, x, y, size, 0, 0);
            } else {
                /* output a run of pixels from imagedata_buffer */
                if (imagedata_size < size)
                    break;
                xan_wc3_output_pixel_run(s, frame, imagedata_buffer, x, y, size);
                imagedata_buffer += size;
                imagedata_size -= size;
            }
        } else {
            uint8_t vector;
            if (bytestream2_get_bytes_left(&vector_segment) <= 0) {
                av_log(s->avctx, AV_LOG_ERROR, "vector_segment overread\n");
                return AVERROR_INVALIDDATA;
            }
            /* run-based motion compensation from last frame */
            vector = bytestream2_get_byte(&vector_segment);
            motion_x = sign_extend(vector >> 4,  4);
            motion_y = sign_extend(vector & 0xF, 4);

            /* copy a run of pixels from the previous frame */
            xan_wc3_copy_pixel_run(s, frame, x, y, size, motion_x, motion_y);

            flag = 0;
        }

        /* coordinate accounting */
        total_pixels -= size;
        y += (x + size) / width;
        x  = (x + size) % width;
    }
    return 0;
}

#if RUNTIME_GAMMA
static inline unsigned mul(unsigned a, unsigned b)
{
    return (a * b) >> 16;
}

static inline unsigned pow4(unsigned a)
{
    unsigned square = mul(a, a);
    return mul(square, square);
}

static inline unsigned pow5(unsigned a)
{
    return mul(pow4(a), a);
}

static uint8_t gamma_corr(uint8_t in) {
    unsigned lo, hi = 0xff40, target;
    int i = 15;
    in = (in << 2) | (in >> 6);
    /*  equivalent float code:
    if (in >= 252)
        return 253;
    return round(pow(in / 256.0, 0.8) * 256);
    */
    lo = target = in << 8;
    do {
        unsigned mid = (lo + hi) >> 1;
        unsigned pow = pow5(mid);
        if (pow > target) hi = mid;
        else lo = mid;
    } while (--i);
    return (pow4((lo + hi) >> 1) + 0x80) >> 8;
}
#else
/**
 * This is a gamma correction that xan3 applies to all palette entries.
 *
 * There is a peculiarity, namely that the values are clamped to 253 -
 * it seems likely that this table was calculated by a buggy fixed-point
 * implementation, the one above under RUNTIME_GAMMA behaves like this for
 * example.
 * The exponent value of 0.8 can be explained by this as well, since 0.8 = 4/5
 * and thus pow(x, 0.8) is still easy to calculate.
 * Also, the input values are first rotated to the left by 2.
 */
static const uint8_t gamma_lookup[256] = {
    0x00, 0x09, 0x10, 0x16, 0x1C, 0x21, 0x27, 0x2C,
    0x31, 0x35, 0x3A, 0x3F, 0x43, 0x48, 0x4C, 0x50,
    0x54, 0x59, 0x5D, 0x61, 0x65, 0x69, 0x6D, 0x71,
    0x75, 0x79, 0x7D, 0x80, 0x84, 0x88, 0x8C, 0x8F,
    0x93, 0x97, 0x9A, 0x9E, 0xA2, 0xA5, 0xA9, 0xAC,
    0xB0, 0xB3, 0xB7, 0xBA, 0xBE, 0xC1, 0xC5, 0xC8,
    0xCB, 0xCF, 0xD2, 0xD5, 0xD9, 0xDC, 0xDF, 0xE3,
    0xE6, 0xE9, 0xED, 0xF0, 0xF3, 0xF6, 0xFA, 0xFD,
    0x03, 0x0B, 0x12, 0x18, 0x1D, 0x23, 0x28, 0x2D,
    0x32, 0x36, 0x3B, 0x40, 0x44, 0x49, 0x4D, 0x51,
    0x56, 0x5A, 0x5E, 0x62, 0x66, 0x6A, 0x6E, 0x72,
    0x76, 0x7A, 0x7D, 0x81, 0x85, 0x89, 0x8D, 0x90,
    0x94, 0x98, 0x9B, 0x9F, 0xA2, 0xA6, 0xAA, 0xAD,
    0xB1, 0xB4, 0xB8, 0xBB, 0xBF, 0xC2, 0xC5, 0xC9,
    0xCC, 0xD0, 0xD3, 0xD6, 0xDA, 0xDD, 0xE0, 0xE4,
    0xE7, 0xEA, 0xED, 0xF1, 0xF4, 0xF7, 0xFA, 0xFD,
    0x05, 0x0D, 0x13, 0x19, 0x1F, 0x24, 0x29, 0x2E,
    0x33, 0x38, 0x3C, 0x41, 0x45, 0x4A, 0x4E, 0x52,
    0x57, 0x5B, 0x5F, 0x63, 0x67, 0x6B, 0x6F, 0x73,
    0x77, 0x7B, 0x7E, 0x82, 0x86, 0x8A, 0x8D, 0x91,
    0x95, 0x99, 0x9C, 0xA0, 0xA3, 0xA7, 0xAA, 0xAE,
    0xB2, 0xB5, 0xB9, 0xBC, 0xBF, 0xC3, 0xC6, 0xCA,
    0xCD, 0xD0, 0xD4, 0xD7, 0xDA, 0xDE, 0xE1, 0xE4,
    0xE8, 0xEB, 0xEE, 0xF1, 0xF5, 0xF8, 0xFB, 0xFD,
    0x07, 0x0E, 0x15, 0x1A, 0x20, 0x25, 0x2A, 0x2F,
    0x34, 0x39, 0x3D, 0x42, 0x46, 0x4B, 0x4F, 0x53,
    0x58, 0x5C, 0x60, 0x64, 0x68, 0x6C, 0x70, 0x74,
    0x78, 0x7C, 0x7F, 0x83, 0x87, 0x8B, 0x8E, 0x92,
    0x96, 0x99, 0x9D, 0xA1, 0xA4, 0xA8, 0xAB, 0xAF,
    0xB2, 0xB6, 0xB9, 0xBD, 0xC0, 0xC4, 0xC7, 0xCB,
    0xCE, 0xD1, 0xD5, 0xD8, 0xDB, 0xDF, 0xE2, 0xE5,
    0xE9, 0xEC, 0xEF, 0xF2, 0xF6, 0xF9, 0xFC, 0xFD
};
#endif

static int xan_decode_frame(AVCodecContext *avctx,
                            void *data, int *got_frame,
                            AVPacket *avpkt)
{
    AVFrame *frame = data;
    const uint8_t *buf = avpkt->data;
    int ret, buf_size = avpkt->size;
    XanContext *s = avctx->priv_data;
    GetByteContext ctx;
    int tag = 0;

    bytestream2_init(&ctx, buf, buf_size);
    while (bytestream2_get_bytes_left(&ctx) > 8 && tag != VGA__TAG) {
        unsigned *tmpptr;
        uint32_t new_pal;
        int size;
        int i;
        tag  = bytestream2_get_le32(&ctx);
        size = bytestream2_get_be32(&ctx);
        if (size < 0) {
            av_log(avctx, AV_LOG_ERROR, "Invalid tag size %d\n", size);
            return AVERROR_INVALIDDATA;
        }
        size = FFMIN(size, bytestream2_get_bytes_left(&ctx));
        switch (tag) {
        case PALT_TAG:
            if (size < PALETTE_SIZE)
                return AVERROR_INVALIDDATA;
            if (s->palettes_count >= PALETTES_MAX)
                return AVERROR_INVALIDDATA;
            tmpptr = av_realloc_array(s->palettes,
                                      s->palettes_count + 1, AVPALETTE_SIZE);
            if (!tmpptr)
                return AVERROR(ENOMEM);
            s->palettes = tmpptr;
            tmpptr += s->palettes_count * AVPALETTE_COUNT;
            for (i = 0; i < PALETTE_COUNT; i++) {
#if RUNTIME_GAMMA
                int r = gamma_corr(bytestream2_get_byteu(&ctx));
                int g = gamma_corr(bytestream2_get_byteu(&ctx));
                int b = gamma_corr(bytestream2_get_byteu(&ctx));
#else
                int r = gamma_lookup[bytestream2_get_byteu(&ctx)];
                int g = gamma_lookup[bytestream2_get_byteu(&ctx)];
                int b = gamma_lookup[bytestream2_get_byteu(&ctx)];
#endif
                *tmpptr++ = (0xFFU << 24) | (r << 16) | (g << 8) | b;
            }
            s->palettes_count++;
            break;
        case SHOT_TAG:
            if (size < 4)
                return AVERROR_INVALIDDATA;
            new_pal = bytestream2_get_le32(&ctx);
            if (new_pal < s->palettes_count) {
                s->cur_palette = new_pal;
            } else
                av_log(avctx, AV_LOG_ERROR, "Invalid palette selected\n");
            break;
        case VGA__TAG:
            break;
        default:
            bytestream2_skip(&ctx, size);
            break;
        }
    }
    buf_size = bytestream2_get_bytes_left(&ctx);

    if (s->palettes_count <= 0) {
        av_log(s->avctx, AV_LOG_ERROR, "No palette found\n");
        return AVERROR_INVALIDDATA;
    }

    if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
        return ret;

    if (!s->frame_size)
        s->frame_size = frame->linesize[0] * s->avctx->height;

    memcpy(frame->data[1],
           s->palettes + s->cur_palette * AVPALETTE_COUNT, AVPALETTE_SIZE);

    s->buf = ctx.buffer;
    s->size = buf_size;

    if (xan_wc3_decode_frame(s, frame) < 0)
        return AVERROR_INVALIDDATA;

    av_frame_unref(s->last_frame);
    if ((ret = av_frame_ref(s->last_frame, frame)) < 0)
        return ret;

    *got_frame = 1;

    /* always report that the buffer was completely consumed */
    return buf_size;
}

AVCodec ff_xan_wc3_decoder = {
    .name           = "xan_wc3",
    .long_name      = NULL_IF_CONFIG_SMALL("Wing Commander III / Xan"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_XAN_WC3,
    .priv_data_size = sizeof(XanContext),
    .init           = xan_decode_init,
    .close          = xan_decode_end,
    .decode         = xan_decode_frame,
    .capabilities   = AV_CODEC_CAP_DR1,
};