2 * Wing Commander/Xan Video Decoder
3 * Copyright (C) 2003 the ffmpeg project
5 * This file is part of FFmpeg.
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 * Xan video decoder for Wing Commander III computer game
26 * by Mario Brito (mbrito@student.dei.uc.pt)
27 * and Mike Melanson (melanson@pcisys.net)
29 * The xan_wc3 decoder outputs PAL8 data.
39 typedef struct XanContext {
41 AVCodecContext *avctx;
43 AVFrame current_frame;
49 unsigned char *buffer1;
51 unsigned char *buffer2;
58 static int xan_decode_init(AVCodecContext *avctx)
60 XanContext *s = avctx->priv_data;
65 if ((avctx->codec->id == CODEC_ID_XAN_WC3) &&
66 (s->avctx->palctrl == NULL)) {
67 av_log(avctx, AV_LOG_ERROR, " WC3 Xan video: palette expected.\n");
71 avctx->pix_fmt = PIX_FMT_PAL8;
73 if(avcodec_check_dimensions(avctx, avctx->width, avctx->height))
76 s->buffer1_size = avctx->width * avctx->height;
77 s->buffer1 = av_malloc(s->buffer1_size);
78 s->buffer2_size = avctx->width * avctx->height;
79 s->buffer2 = av_malloc(s->buffer2_size);
80 if (!s->buffer1 || !s->buffer2)
86 /* This function is used in lieu of memcpy(). This decoder cannot use
87 * memcpy because the memory locations often overlap and
88 * memcpy doesn't like that; it's not uncommon, for example, for
89 * dest = src+1, to turn byte A into pattern AAAAAAAA.
90 * This was originally repz movsb in Intel x86 ASM. */
91 static inline void bytecopy(unsigned char *dest, unsigned char *src, int count)
95 for (i = 0; i < count; i++)
99 static int xan_huffman_decode(unsigned char *dest, unsigned char *src,
102 unsigned char byte = *src++;
103 unsigned char ival = byte + 0x16;
104 unsigned char * ptr = src + byte*2;
105 unsigned char val = ival;
107 unsigned char *dest_end = dest + dest_len;
109 unsigned char bits = *ptr++;
111 while ( val != 0x16 ) {
112 if ( (1 << counter) & bits )
113 val = src[byte + val - 0x17];
115 val = src[val - 0x17];
118 if (dest + 1 > dest_end)
124 if (counter++ == 7) {
133 static void xan_unpack(unsigned char *dest, unsigned char *src, int dest_len)
135 unsigned char opcode;
138 int byte1, byte2, byte3;
139 unsigned char *dest_end = dest + dest_len;
144 if ( (opcode & 0x80) == 0 ) {
149 if (dest + size > dest_end)
151 bytecopy(dest, src, size); dest += size; src += size;
153 size = ((opcode & 0x1c) >> 2) + 3;
154 if (dest + size > dest_end)
156 bytecopy (dest, dest - (((opcode & 0x60) << 3) + offset + 1), size);
159 } else if ( (opcode & 0x40) == 0 ) {
165 if (dest + size > dest_end)
167 bytecopy (dest, src, size); dest += size; src += size;
169 size = (opcode & 0x3f) + 4;
170 if (dest + size > dest_end)
172 bytecopy (dest, dest - (((byte1 & 0x3f) << 8) + byte2 + 1), size);
175 } else if ( (opcode & 0x20) == 0 ) {
182 if (dest + size > dest_end)
184 bytecopy (dest, src, size); dest += size; src += size;
186 size = byte3 + 5 + ((opcode & 0xc) << 6);
187 if (dest + size > dest_end)
190 dest - ((((opcode & 0x10) >> 4) << 0x10) + 1 + (byte1 << 8) + byte2),
194 size = ((opcode & 0x1f) << 2) + 4;
199 if (dest + size > dest_end)
201 bytecopy (dest, src, size); dest += size; src += size;
206 bytecopy(dest, src, size); dest += size; src += size;
209 static inline void xan_wc3_output_pixel_run(XanContext *s,
210 unsigned char *pixel_buffer, int x, int y, int pixel_count)
216 int width = s->avctx->width;
217 unsigned char *palette_plane;
219 palette_plane = s->current_frame.data[0];
220 stride = s->current_frame.linesize[0];
221 line_inc = stride - width;
222 index = y * stride + x;
224 while((pixel_count--) && (index < s->frame_size)) {
226 /* don't do a memcpy() here; keyframes generally copy an entire
227 * frame of data and the stride needs to be accounted for */
228 palette_plane[index++] = *pixel_buffer++;
231 if (current_x >= width) {
238 static inline void xan_wc3_copy_pixel_run(XanContext *s,
239 int x, int y, int pixel_count, int motion_x, int motion_y)
243 int curframe_index, prevframe_index;
244 int curframe_x, prevframe_x;
245 int width = s->avctx->width;
246 unsigned char *palette_plane, *prev_palette_plane;
248 palette_plane = s->current_frame.data[0];
249 prev_palette_plane = s->last_frame.data[0];
250 stride = s->current_frame.linesize[0];
251 line_inc = stride - width;
252 curframe_index = y * stride + x;
254 prevframe_index = (y + motion_y) * stride + x + motion_x;
255 prevframe_x = x + motion_x;
256 while((pixel_count--) && (curframe_index < s->frame_size)) {
258 palette_plane[curframe_index++] =
259 prev_palette_plane[prevframe_index++];
262 if (curframe_x >= width) {
263 curframe_index += line_inc;
268 if (prevframe_x >= width) {
269 prevframe_index += line_inc;
275 static void xan_wc3_decode_frame(XanContext *s) {
277 int width = s->avctx->width;
278 int height = s->avctx->height;
279 int total_pixels = width * height;
280 unsigned char opcode;
281 unsigned char flag = 0;
283 int motion_x, motion_y;
286 unsigned char *opcode_buffer = s->buffer1;
287 int opcode_buffer_size = s->buffer1_size;
288 unsigned char *imagedata_buffer = s->buffer2;
289 int imagedata_buffer_size = s->buffer2_size;
291 /* pointers to segments inside the compressed chunk */
292 unsigned char *huffman_segment;
293 unsigned char *size_segment;
294 unsigned char *vector_segment;
295 unsigned char *imagedata_segment;
297 huffman_segment = s->buf + AV_RL16(&s->buf[0]);
298 size_segment = s->buf + AV_RL16(&s->buf[2]);
299 vector_segment = s->buf + AV_RL16(&s->buf[4]);
300 imagedata_segment = s->buf + AV_RL16(&s->buf[6]);
302 xan_huffman_decode(opcode_buffer, huffman_segment, opcode_buffer_size);
304 if (imagedata_segment[0] == 2)
305 xan_unpack(imagedata_buffer, &imagedata_segment[1],
306 imagedata_buffer_size);
308 imagedata_buffer = &imagedata_segment[1];
310 /* use the decoded data segments to build the frame */
312 while (total_pixels) {
314 opcode = *opcode_buffer++;
341 size += (opcode - 10);
346 size = *size_segment++;
351 size = AV_RB16(&size_segment[0]);
357 size = AV_RB24(size_segment);
365 /* run of (size) pixels is unchanged from last frame */
366 xan_wc3_copy_pixel_run(s, x, y, size, 0, 0);
368 /* output a run of pixels from imagedata_buffer */
369 xan_wc3_output_pixel_run(s, imagedata_buffer, x, y, size);
370 imagedata_buffer += size;
373 /* run-based motion compensation from last frame */
374 motion_x = (*vector_segment >> 4) & 0xF;
375 motion_y = *vector_segment & 0xF;
380 motion_x |= 0xFFFFFFF0;
382 motion_y |= 0xFFFFFFF0;
384 /* copy a run of pixels from the previous frame */
385 xan_wc3_copy_pixel_run(s, x, y, size, motion_x, motion_y);
390 /* coordinate accounting */
391 total_pixels -= size;
393 if (x + size >= width) {
405 static void xan_wc4_decode_frame(XanContext *s) {
408 static int xan_decode_frame(AVCodecContext *avctx,
409 void *data, int *data_size,
410 uint8_t *buf, int buf_size)
412 XanContext *s = avctx->priv_data;
413 AVPaletteControl *palette_control = avctx->palctrl;
415 if (avctx->get_buffer(avctx, &s->current_frame)) {
416 av_log(s->avctx, AV_LOG_ERROR, " Xan Video: get_buffer() failed\n");
419 s->current_frame.reference = 3;
422 s->frame_size = s->current_frame.linesize[0] * s->avctx->height;
424 palette_control->palette_changed = 0;
425 memcpy(s->current_frame.data[1], palette_control->palette,
427 s->current_frame.palette_has_changed = 1;
432 if (avctx->codec->id == CODEC_ID_XAN_WC3)
433 xan_wc3_decode_frame(s);
434 else if (avctx->codec->id == CODEC_ID_XAN_WC4)
435 xan_wc4_decode_frame(s);
437 /* release the last frame if it is allocated */
438 if (s->last_frame.data[0])
439 avctx->release_buffer(avctx, &s->last_frame);
442 s->last_frame = s->current_frame;
444 *data_size = sizeof(AVFrame);
445 *(AVFrame*)data = s->current_frame;
447 /* always report that the buffer was completely consumed */
451 static int xan_decode_end(AVCodecContext *avctx)
453 XanContext *s = avctx->priv_data;
455 /* release the last frame */
456 if (s->last_frame.data[0])
457 avctx->release_buffer(avctx, &s->last_frame);
465 AVCodec xan_wc3_decoder = {
478 AVCodec xan_wc4_decoder = {