2 * Wing Commander/Xan Video Decoder
3 * Copyright (C) 2003 the ffmpeg project
5 * This file is part of Libav.
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * Xan video decoder for Wing Commander III computer game
25 * by Mario Brito (mbrito@student.dei.uc.pt)
26 * and Mike Melanson (melanson@pcisys.net)
28 * The xan_wc3 decoder outputs PAL8 data.
35 #include "libavutil/intreadwrite.h"
36 #include "libavutil/mem.h"
38 #include "bytestream.h"
39 #define BITSTREAM_READER_LE
42 #define RUNTIME_GAMMA 0
44 #define VGA__TAG MKTAG('V', 'G', 'A', ' ')
45 #define PALT_TAG MKTAG('P', 'A', 'L', 'T')
46 #define SHOT_TAG MKTAG('S', 'H', 'O', 'T')
47 #define PALETTE_COUNT 256
48 #define PALETTE_SIZE (PALETTE_COUNT * 3)
49 #define PALETTES_MAX 256
51 typedef struct XanContext {
53 AVCodecContext *avctx;
55 AVFrame current_frame;
57 const unsigned char *buf;
61 unsigned char *buffer1;
63 unsigned char *buffer2;
74 static av_cold int xan_decode_init(AVCodecContext *avctx)
76 XanContext *s = avctx->priv_data;
81 avctx->pix_fmt = AV_PIX_FMT_PAL8;
83 s->buffer1_size = avctx->width * avctx->height;
84 s->buffer1 = av_malloc(s->buffer1_size);
86 return AVERROR(ENOMEM);
87 s->buffer2_size = avctx->width * avctx->height;
88 s->buffer2 = av_malloc(s->buffer2_size + 130);
90 av_freep(&s->buffer1);
91 return AVERROR(ENOMEM);
97 static int xan_huffman_decode(unsigned char *dest, int dest_len,
98 const unsigned char *src, int src_len)
100 unsigned char byte = *src++;
101 unsigned char ival = byte + 0x16;
102 const unsigned char * ptr = src + byte*2;
103 int ptr_len = src_len - 1 - byte*2;
104 unsigned char val = ival;
105 unsigned char *dest_end = dest + dest_len;
109 return AVERROR_INVALIDDATA;
111 init_get_bits(&gb, ptr, ptr_len * 8);
113 while (val != 0x16) {
114 unsigned idx = val - 0x17 + get_bits1(&gb) * byte;
120 if (dest >= dest_end)
131 * unpack simple compression
133 * @param dest destination buffer of dest_len, must be padded with at least 130 bytes
135 static void xan_unpack(unsigned char *dest, int dest_len,
136 const unsigned char *src, int src_len)
138 unsigned char opcode;
140 unsigned char *dest_org = dest;
141 unsigned char *dest_end = dest + dest_len;
142 const unsigned char *src_end = src + src_len;
144 while (dest < dest_end && src < src_end) {
149 if ((opcode & 0x80) == 0) {
152 back = ((opcode & 0x60) << 3) + *src++ + 1;
153 size2 = ((opcode & 0x1c) >> 2) + 3;
154 } else if ((opcode & 0x40) == 0) {
157 back = (bytestream_get_be16(&src) & 0x3fff) + 1;
158 size2 = (opcode & 0x3f) + 4;
162 back = ((opcode & 0x10) << 12) + bytestream_get_be16(&src) + 1;
163 size2 = ((opcode & 0x0c) << 6) + *src++ + 5;
166 if (dest_end - dest < size + size2 ||
167 dest + size - dest_org < back ||
168 src_end - src < size)
170 memcpy(dest, src, size); dest += size; src += size;
171 av_memcpy_backptr(dest, back, size2);
174 int finish = opcode >= 0xfc;
175 size = finish ? opcode & 3 : ((opcode & 0x1f) << 2) + 4;
177 if (dest_end - dest < size || src_end - src < size)
179 memcpy(dest, src, size); dest += size; src += size;
186 static inline void xan_wc3_output_pixel_run(XanContext *s,
187 const unsigned char *pixel_buffer, int x, int y, int pixel_count)
193 int width = s->avctx->width;
194 unsigned char *palette_plane;
196 palette_plane = s->current_frame.data[0];
197 stride = s->current_frame.linesize[0];
198 line_inc = stride - width;
199 index = y * stride + x;
201 while (pixel_count && index < s->frame_size) {
202 int count = FFMIN(pixel_count, width - current_x);
203 memcpy(palette_plane + index, pixel_buffer, count);
204 pixel_count -= count;
206 pixel_buffer += count;
209 if (current_x >= width) {
216 static inline void xan_wc3_copy_pixel_run(XanContext *s, int x, int y,
217 int pixel_count, int motion_x,
222 int curframe_index, prevframe_index;
223 int curframe_x, prevframe_x;
224 int width = s->avctx->width;
225 unsigned char *palette_plane, *prev_palette_plane;
227 if (y + motion_y < 0 || y + motion_y >= s->avctx->height ||
228 x + motion_x < 0 || x + motion_x >= s->avctx->width)
231 palette_plane = s->current_frame.data[0];
232 prev_palette_plane = s->last_frame.data[0];
233 if (!prev_palette_plane)
234 prev_palette_plane = palette_plane;
235 stride = s->current_frame.linesize[0];
236 line_inc = stride - width;
237 curframe_index = y * stride + x;
239 prevframe_index = (y + motion_y) * stride + x + motion_x;
240 prevframe_x = x + motion_x;
241 while (pixel_count &&
242 curframe_index < s->frame_size &&
243 prevframe_index < s->frame_size) {
244 int count = FFMIN3(pixel_count, width - curframe_x,
245 width - prevframe_x);
247 memcpy(palette_plane + curframe_index,
248 prev_palette_plane + prevframe_index, count);
249 pixel_count -= count;
250 curframe_index += count;
251 prevframe_index += count;
253 prevframe_x += count;
255 if (curframe_x >= width) {
256 curframe_index += line_inc;
260 if (prevframe_x >= width) {
261 prevframe_index += line_inc;
267 static int xan_wc3_decode_frame(XanContext *s) {
269 int width = s->avctx->width;
270 int height = s->avctx->height;
271 int total_pixels = width * height;
272 unsigned char opcode;
273 unsigned char flag = 0;
275 int motion_x, motion_y;
278 unsigned char *opcode_buffer = s->buffer1;
279 unsigned char *opcode_buffer_end = s->buffer1 + s->buffer1_size;
280 int opcode_buffer_size = s->buffer1_size;
281 const unsigned char *imagedata_buffer = s->buffer2;
283 /* pointers to segments inside the compressed chunk */
284 const unsigned char *huffman_segment;
285 const unsigned char *size_segment;
286 const unsigned char *vector_segment;
287 const unsigned char *imagedata_segment;
288 int huffman_offset, size_offset, vector_offset, imagedata_offset,
292 return AVERROR_INVALIDDATA;
294 huffman_offset = AV_RL16(&s->buf[0]);
295 size_offset = AV_RL16(&s->buf[2]);
296 vector_offset = AV_RL16(&s->buf[4]);
297 imagedata_offset = AV_RL16(&s->buf[6]);
299 if (huffman_offset >= s->size ||
300 size_offset >= s->size ||
301 vector_offset >= s->size ||
302 imagedata_offset >= s->size)
303 return AVERROR_INVALIDDATA;
305 huffman_segment = s->buf + huffman_offset;
306 size_segment = s->buf + size_offset;
307 vector_segment = s->buf + vector_offset;
308 imagedata_segment = s->buf + imagedata_offset;
310 if (xan_huffman_decode(opcode_buffer, opcode_buffer_size,
311 huffman_segment, s->size - huffman_offset) < 0)
312 return AVERROR_INVALIDDATA;
314 if (imagedata_segment[0] == 2) {
315 xan_unpack(s->buffer2, s->buffer2_size,
316 &imagedata_segment[1], s->size - imagedata_offset - 1);
317 imagedata_size = s->buffer2_size;
319 imagedata_size = s->size - imagedata_offset - 1;
320 imagedata_buffer = &imagedata_segment[1];
323 /* use the decoded data segments to build the frame */
325 while (total_pixels && opcode_buffer < opcode_buffer_end) {
327 opcode = *opcode_buffer++;
354 size += (opcode - 10);
359 size = *size_segment++;
364 size = AV_RB16(&size_segment[0]);
370 size = AV_RB24(size_segment);
375 if (size > total_pixels)
381 /* run of (size) pixels is unchanged from last frame */
382 xan_wc3_copy_pixel_run(s, x, y, size, 0, 0);
384 /* output a run of pixels from imagedata_buffer */
385 if (imagedata_size < size)
387 xan_wc3_output_pixel_run(s, imagedata_buffer, x, y, size);
388 imagedata_buffer += size;
389 imagedata_size -= size;
392 /* run-based motion compensation from last frame */
393 motion_x = sign_extend(*vector_segment >> 4, 4);
394 motion_y = sign_extend(*vector_segment & 0xF, 4);
397 /* copy a run of pixels from the previous frame */
398 xan_wc3_copy_pixel_run(s, x, y, size, motion_x, motion_y);
403 /* coordinate accounting */
404 total_pixels -= size;
405 y += (x + size) / width;
406 x = (x + size) % width;
412 static inline unsigned mul(unsigned a, unsigned b)
414 return (a * b) >> 16;
417 static inline unsigned pow4(unsigned a)
419 unsigned square = mul(a, a);
420 return mul(square, square);
423 static inline unsigned pow5(unsigned a)
425 return mul(pow4(a), a);
428 static uint8_t gamma_corr(uint8_t in) {
429 unsigned lo, hi = 0xff40, target;
431 in = (in << 2) | (in >> 6);
432 /* equivalent float code:
435 return round(pow(in / 256.0, 0.8) * 256);
437 lo = target = in << 8;
439 unsigned mid = (lo + hi) >> 1;
440 unsigned pow = pow5(mid);
441 if (pow > target) hi = mid;
444 return (pow4((lo + hi) >> 1) + 0x80) >> 8;
448 * This is a gamma correction that xan3 applies to all palette entries.
450 * There is a peculiarity, namely that the values are clamped to 253 -
451 * it seems likely that this table was calculated by a buggy fixed-point
452 * implementation, the one above under RUNTIME_GAMMA behaves like this for
454 * The exponent value of 0.8 can be explained by this as well, since 0.8 = 4/5
455 * and thus pow(x, 0.8) is still easy to calculate.
456 * Also, the input values are first rotated to the left by 2.
458 static const uint8_t gamma_lookup[256] = {
459 0x00, 0x09, 0x10, 0x16, 0x1C, 0x21, 0x27, 0x2C,
460 0x31, 0x35, 0x3A, 0x3F, 0x43, 0x48, 0x4C, 0x50,
461 0x54, 0x59, 0x5D, 0x61, 0x65, 0x69, 0x6D, 0x71,
462 0x75, 0x79, 0x7D, 0x80, 0x84, 0x88, 0x8C, 0x8F,
463 0x93, 0x97, 0x9A, 0x9E, 0xA2, 0xA5, 0xA9, 0xAC,
464 0xB0, 0xB3, 0xB7, 0xBA, 0xBE, 0xC1, 0xC5, 0xC8,
465 0xCB, 0xCF, 0xD2, 0xD5, 0xD9, 0xDC, 0xDF, 0xE3,
466 0xE6, 0xE9, 0xED, 0xF0, 0xF3, 0xF6, 0xFA, 0xFD,
467 0x03, 0x0B, 0x12, 0x18, 0x1D, 0x23, 0x28, 0x2D,
468 0x32, 0x36, 0x3B, 0x40, 0x44, 0x49, 0x4D, 0x51,
469 0x56, 0x5A, 0x5E, 0x62, 0x66, 0x6A, 0x6E, 0x72,
470 0x76, 0x7A, 0x7D, 0x81, 0x85, 0x89, 0x8D, 0x90,
471 0x94, 0x98, 0x9B, 0x9F, 0xA2, 0xA6, 0xAA, 0xAD,
472 0xB1, 0xB4, 0xB8, 0xBB, 0xBF, 0xC2, 0xC5, 0xC9,
473 0xCC, 0xD0, 0xD3, 0xD6, 0xDA, 0xDD, 0xE0, 0xE4,
474 0xE7, 0xEA, 0xED, 0xF1, 0xF4, 0xF7, 0xFA, 0xFD,
475 0x05, 0x0D, 0x13, 0x19, 0x1F, 0x24, 0x29, 0x2E,
476 0x33, 0x38, 0x3C, 0x41, 0x45, 0x4A, 0x4E, 0x52,
477 0x57, 0x5B, 0x5F, 0x63, 0x67, 0x6B, 0x6F, 0x73,
478 0x77, 0x7B, 0x7E, 0x82, 0x86, 0x8A, 0x8D, 0x91,
479 0x95, 0x99, 0x9C, 0xA0, 0xA3, 0xA7, 0xAA, 0xAE,
480 0xB2, 0xB5, 0xB9, 0xBC, 0xBF, 0xC3, 0xC6, 0xCA,
481 0xCD, 0xD0, 0xD4, 0xD7, 0xDA, 0xDE, 0xE1, 0xE4,
482 0xE8, 0xEB, 0xEE, 0xF1, 0xF5, 0xF8, 0xFB, 0xFD,
483 0x07, 0x0E, 0x15, 0x1A, 0x20, 0x25, 0x2A, 0x2F,
484 0x34, 0x39, 0x3D, 0x42, 0x46, 0x4B, 0x4F, 0x53,
485 0x58, 0x5C, 0x60, 0x64, 0x68, 0x6C, 0x70, 0x74,
486 0x78, 0x7C, 0x7F, 0x83, 0x87, 0x8B, 0x8E, 0x92,
487 0x96, 0x99, 0x9D, 0xA1, 0xA4, 0xA8, 0xAB, 0xAF,
488 0xB2, 0xB6, 0xB9, 0xBD, 0xC0, 0xC4, 0xC7, 0xCB,
489 0xCE, 0xD1, 0xD5, 0xD8, 0xDB, 0xDF, 0xE2, 0xE5,
490 0xE9, 0xEC, 0xEF, 0xF2, 0xF6, 0xF9, 0xFC, 0xFD
494 static int xan_decode_frame(AVCodecContext *avctx,
495 void *data, int *data_size,
498 const uint8_t *buf = avpkt->data;
499 int ret, buf_size = avpkt->size;
500 XanContext *s = avctx->priv_data;
502 if (avctx->codec->id == AV_CODEC_ID_XAN_WC3) {
503 const uint8_t *buf_end = buf + buf_size;
505 while (buf_end - buf > 8 && tag != VGA__TAG) {
510 tag = bytestream_get_le32(&buf);
511 size = bytestream_get_be32(&buf);
512 size = FFMIN(size, buf_end - buf);
515 if (size < PALETTE_SIZE)
516 return AVERROR_INVALIDDATA;
517 if (s->palettes_count >= PALETTES_MAX)
518 return AVERROR_INVALIDDATA;
519 tmpptr = av_realloc(s->palettes,
520 (s->palettes_count + 1) * AVPALETTE_SIZE);
522 return AVERROR(ENOMEM);
523 s->palettes = tmpptr;
524 tmpptr += s->palettes_count * AVPALETTE_COUNT;
525 for (i = 0; i < PALETTE_COUNT; i++) {
527 int r = gamma_corr(*buf++);
528 int g = gamma_corr(*buf++);
529 int b = gamma_corr(*buf++);
531 int r = gamma_lookup[*buf++];
532 int g = gamma_lookup[*buf++];
533 int b = gamma_lookup[*buf++];
535 *tmpptr++ = (r << 16) | (g << 8) | b;
541 return AVERROR_INVALIDDATA;
542 new_pal = bytestream_get_le32(&buf);
543 if (new_pal < s->palettes_count) {
544 s->cur_palette = new_pal;
546 av_log(avctx, AV_LOG_ERROR, "Invalid palette selected\n");
555 buf_size = buf_end - buf;
557 if (s->palettes_count <= 0) {
558 av_log(s->avctx, AV_LOG_ERROR, "No palette found\n");
559 return AVERROR_INVALIDDATA;
562 if ((ret = avctx->get_buffer(avctx, &s->current_frame))) {
563 av_log(s->avctx, AV_LOG_ERROR, "get_buffer() failed\n");
566 s->current_frame.reference = 3;
569 s->frame_size = s->current_frame.linesize[0] * s->avctx->height;
571 memcpy(s->current_frame.data[1],
572 s->palettes + s->cur_palette * AVPALETTE_COUNT, AVPALETTE_SIZE);
577 if (xan_wc3_decode_frame(s) < 0)
578 return AVERROR_INVALIDDATA;
580 /* release the last frame if it is allocated */
581 if (s->last_frame.data[0])
582 avctx->release_buffer(avctx, &s->last_frame);
584 *data_size = sizeof(AVFrame);
585 *(AVFrame*)data = s->current_frame;
588 FFSWAP(AVFrame, s->current_frame, s->last_frame);
590 /* always report that the buffer was completely consumed */
594 static av_cold int xan_decode_end(AVCodecContext *avctx)
596 XanContext *s = avctx->priv_data;
598 /* release the frames */
599 if (s->last_frame.data[0])
600 avctx->release_buffer(avctx, &s->last_frame);
601 if (s->current_frame.data[0])
602 avctx->release_buffer(avctx, &s->current_frame);
604 av_freep(&s->buffer1);
605 av_freep(&s->buffer2);
606 av_freep(&s->palettes);
611 AVCodec ff_xan_wc3_decoder = {
613 .type = AVMEDIA_TYPE_VIDEO,
614 .id = AV_CODEC_ID_XAN_WC3,
615 .priv_data_size = sizeof(XanContext),
616 .init = xan_decode_init,
617 .close = xan_decode_end,
618 .decode = xan_decode_frame,
619 .capabilities = CODEC_CAP_DR1,
620 .long_name = NULL_IF_CONFIG_SMALL("Wing Commander III / Xan"),