2 * Discworld II BMV video decoder
3 * Copyright (c) 2011 Konstantin Shishkov
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
22 #include "libavutil/common.h"
25 #include "bytestream.h"
42 #define SCREEN_WIDE 640
43 #define SCREEN_HIGH 429
45 typedef struct BMVDecContext {
46 AVCodecContext *avctx;
48 uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)];
50 const uint8_t *stream;
53 #define NEXT_BYTE(v) v = forward ? v + 1 : v - 1;
55 static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
57 unsigned val, saved_val = 0;
59 const uint8_t *src, *source_end = source + src_len;
60 uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
61 uint8_t *dst, *dst_end;
63 int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
64 int read_two_nibbles, flag;
70 return AVERROR_INVALIDDATA;
77 src = source + src_len - 1;
85 /* The mode/len decoding is a bit strange:
86 * values are coded as variable-length codes with nibble units,
87 * code end is signalled by two top bits in the nibble being nonzero.
88 * And since data is bytepacked and we read two nibbles at a time,
89 * we may get a nibble belonging to the next code.
90 * Hence this convoluted loop.
92 if (!mode || (tmplen == 4)) {
93 if (src < source || src >= source_end)
94 return AVERROR_INVALIDDATA;
103 if (!read_two_nibbles) {
104 if (src < source || src >= source_end)
105 return AVERROR_INVALIDDATA;
107 val |= *src << shift;
111 // two upper bits of the nibble is zero,
112 // so shift top nibble value down into their place
113 read_two_nibbles = 0;
115 mask = (1 << shift) - 1;
116 val = ((val >> 2) & ~mask) | (val & mask);
118 if ((val & (0xC << shift))) {
129 saved_val = val >> (4 + shift);
131 val &= (1 << (shift + 4)) - 1;
134 advance_mode = val & 1;
135 len = (val >> 1) - 1;
136 mode += 1 + advance_mode;
139 if (len <= 0 || FFABS(dst_end - dst) < len)
140 return AVERROR_INVALIDDATA;
144 if (dst - frame + SCREEN_WIDE < frame_off ||
145 dst - frame + SCREEN_WIDE + frame_off < 0 ||
146 frame_end - dst < frame_off + len ||
147 frame_end - dst < len)
148 return AVERROR_INVALIDDATA;
149 for (i = 0; i < len; i++)
150 dst[i] = dst[frame_off + i];
154 if (dst - frame + SCREEN_WIDE < frame_off ||
155 dst - frame + SCREEN_WIDE + frame_off < 0 ||
156 frame_end - dst < frame_off + len ||
157 frame_end - dst < len)
158 return AVERROR_INVALIDDATA;
159 for (i = len - 1; i >= 0; i--)
160 dst[i] = dst[frame_off + i];
165 if (source + src_len - src < len)
166 return AVERROR_INVALIDDATA;
167 memcpy(dst, src, len);
171 if (src - source < len)
172 return AVERROR_INVALIDDATA;
175 memcpy(dst, src, len);
179 val = forward ? dst[-1] : dst[1];
181 memset(dst, val, len);
185 memset(dst, val, len);
196 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
199 BMVDecContext * const c = avctx->priv_data;
200 AVFrame *frame = data;
203 uint8_t *srcptr, *outptr;
205 c->stream = pkt->data;
206 type = bytestream_get_byte(&c->stream);
207 if (type & BMV_AUDIO) {
208 int blobs = bytestream_get_byte(&c->stream);
209 if (pkt->size < blobs * 65 + 2) {
210 av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
211 return AVERROR_INVALIDDATA;
213 c->stream += blobs * 65;
215 if (type & BMV_COMMAND) {
216 int command_size = (type & BMV_PRINT) ? 8 : 10;
217 if (c->stream - pkt->data + command_size > pkt->size) {
218 av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
219 return AVERROR_INVALIDDATA;
221 c->stream += command_size;
223 if (type & BMV_PALETTE) {
224 if (c->stream - pkt->data > pkt->size - 768) {
225 av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
226 return AVERROR_INVALIDDATA;
228 for (i = 0; i < 256; i++)
229 c->pal[i] = bytestream_get_be24(&c->stream);
231 if (type & BMV_SCROLL) {
232 if (c->stream - pkt->data > pkt->size - 2) {
233 av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
234 return AVERROR_INVALIDDATA;
236 scr_off = (int16_t)bytestream_get_le16(&c->stream);
237 } else if ((type & BMV_INTRA) == BMV_INTRA) {
243 if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) {
244 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
248 if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
249 av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
250 return AVERROR_INVALIDDATA;
253 memcpy(frame->data[1], c->pal, AVPALETTE_SIZE);
254 frame->palette_has_changed = type & BMV_PALETTE;
256 outptr = frame->data[0];
259 for (i = 0; i < avctx->height; i++) {
260 memcpy(outptr, srcptr, avctx->width);
261 srcptr += avctx->width;
262 outptr += frame->linesize[0];
267 /* always report that the buffer was completely consumed */
271 static av_cold int decode_init(AVCodecContext *avctx)
273 BMVDecContext * const c = avctx->priv_data;
276 avctx->pix_fmt = AV_PIX_FMT_PAL8;
278 c->frame = c->frame_base + 640;
283 AVCodec ff_bmv_video_decoder = {
285 .long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
286 .type = AVMEDIA_TYPE_VIDEO,
287 .id = AV_CODEC_ID_BMV_VIDEO,
288 .priv_data_size = sizeof(BMVDecContext),
290 .decode = decode_frame,
291 .capabilities = AV_CODEC_CAP_DR1,
292 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,