xref: /third_party/ffmpeg/libavcodec/bmvvideo.c (revision cabdff1a) 
1/*
2 * Discworld II BMV video decoder
3 * Copyright (c) 2011 Konstantin Shishkov
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21
22#include "libavutil/avassert.h"
23#include "libavutil/common.h"
24
25#include "avcodec.h"
26#include "bytestream.h"
27#include "codec_internal.h"
28#include "internal.h"
29
30enum BMVFlags{
31    BMV_NOP = 0,
32    BMV_END,
33    BMV_DELTA,
34    BMV_INTRA,
35
36    BMV_SCROLL  = 0x04,
37    BMV_PALETTE = 0x08,
38    BMV_COMMAND = 0x10,
39    BMV_AUDIO   = 0x20,
40    BMV_EXT     = 0x40,
41    BMV_PRINT   = 0x80
42};
43
44#define SCREEN_WIDE 640
45#define SCREEN_HIGH 429
46
47typedef struct BMVDecContext {
48    AVCodecContext *avctx;
49
50    uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)];
51    uint32_t pal[256];
52    const uint8_t *stream;
53} BMVDecContext;
54
55#define NEXT_BYTE(v) (v) = forward ? (v) + 1 : (v) - 1;
56
57static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
58{
59    unsigned val, saved_val = 0;
60    int tmplen = src_len;
61    const uint8_t *src, *source_end = source + src_len;
62    uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
63    uint8_t *dst, *dst_end;
64    int len, mask;
65    int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
66    int read_two_nibbles, flag;
67    int advance_mode;
68    int mode = 0;
69    int i;
70
71    if (src_len <= 0)
72        return AVERROR_INVALIDDATA;
73
74    if (forward) {
75        src = source;
76        dst = frame;
77        dst_end = frame_end;
78    } else {
79        src = source + src_len - 1;
80        dst = frame_end - 1;
81        dst_end = frame - 1;
82    }
83    for (;;) {
84        int shift = 0;
85        flag = 0;
86
87        /* The mode/len decoding is a bit strange:
88         * values are coded as variable-length codes with nibble units,
89         * code end is signalled by two top bits in the nibble being nonzero.
90         * And since data is bytepacked and we read two nibbles at a time,
91         * we may get a nibble belonging to the next code.
92         * Hence this convoluted loop.
93         */
94        if (!mode || (tmplen == 4)) {
95            if (src < source || src >= source_end)
96                return AVERROR_INVALIDDATA;
97            val = *src;
98            read_two_nibbles = 1;
99        } else {
100            val = saved_val;
101            read_two_nibbles = 0;
102        }
103        if (!(val & 0xC)) {
104            for (;;) {
105                if(shift>22)
106                    return -1;
107                if (!read_two_nibbles) {
108                    if (src < source || src >= source_end)
109                        return AVERROR_INVALIDDATA;
110                    shift += 2;
111                    val |= (unsigned)*src << shift;
112                    if (*src & 0xC)
113                        break;
114                }
115                // two upper bits of the nibble is zero,
116                // so shift top nibble value down into their place
117                read_two_nibbles = 0;
118                shift += 2;
119                mask = (1 << shift) - 1;
120                val = ((val >> 2) & ~mask) | (val & mask);
121                NEXT_BYTE(src);
122                if ((val & (0xC << shift))) {
123                    flag = 1;
124                    break;
125                }
126            }
127        } else if (mode) {
128            flag = tmplen != 4;
129        }
130        if (flag) {
131            tmplen = 4;
132        } else {
133            saved_val = val >> (4 + shift);
134            tmplen = 0;
135            val &= (1 << (shift + 4)) - 1;
136            NEXT_BYTE(src);
137        }
138        advance_mode = val & 1;
139        len = (val >> 1) - 1;
140        av_assert0(len>0);
141        mode += 1 + advance_mode;
142        if (mode >= 4)
143            mode -= 3;
144        if (len <= 0 || FFABS(dst_end - dst) < len)
145            return AVERROR_INVALIDDATA;
146        switch (mode) {
147        case 1:
148            if (forward) {
149                if (dst - frame + SCREEN_WIDE < frame_off ||
150                        dst - frame + SCREEN_WIDE + frame_off < 0 ||
151                        frame_end - dst < frame_off + len ||
152                        frame_end - dst < len)
153                    return AVERROR_INVALIDDATA;
154                for (i = 0; i < len; i++)
155                    dst[i] = dst[frame_off + i];
156                dst += len;
157            } else {
158                dst -= len;
159                if (dst - frame + SCREEN_WIDE < frame_off ||
160                        dst - frame + SCREEN_WIDE + frame_off < 0 ||
161                        frame_end - dst < frame_off + len ||
162                        frame_end - dst < len)
163                    return AVERROR_INVALIDDATA;
164                for (i = len - 1; i >= 0; i--)
165                    dst[i] = dst[frame_off + i];
166            }
167            break;
168        case 2:
169            if (forward) {
170                if (source + src_len - src < len)
171                    return AVERROR_INVALIDDATA;
172                memcpy(dst, src, len);
173                dst += len;
174                src += len;
175            } else {
176                if (src - source < len)
177                    return AVERROR_INVALIDDATA;
178                dst -= len;
179                src -= len;
180                memcpy(dst, src, len);
181            }
182            break;
183        case 3:
184            val = forward ? dst[-1] : dst[1];
185            if (forward) {
186                memset(dst, val, len);
187                dst += len;
188            } else {
189                dst -= len;
190                memset(dst, val, len);
191            }
192            break;
193        }
194        if (dst == dst_end)
195            return 0;
196    }
197}
198
199static int decode_frame(AVCodecContext *avctx, AVFrame *frame,
200                        int *got_frame, AVPacket *pkt)
201{
202    BMVDecContext * const c = avctx->priv_data;
203    int type, scr_off;
204    int i, ret;
205    uint8_t *srcptr, *outptr;
206
207    c->stream = pkt->data;
208    type = bytestream_get_byte(&c->stream);
209    if (type & BMV_AUDIO) {
210        int blobs = bytestream_get_byte(&c->stream);
211        if (pkt->size < blobs * 65 + 2) {
212            av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
213            return AVERROR_INVALIDDATA;
214        }
215        c->stream += blobs * 65;
216    }
217    if (type & BMV_COMMAND) {
218        int command_size = (type & BMV_PRINT) ? 8 : 10;
219        if (c->stream - pkt->data + command_size > pkt->size) {
220            av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
221            return AVERROR_INVALIDDATA;
222        }
223        c->stream += command_size;
224    }
225    if (type & BMV_PALETTE) {
226        if (c->stream - pkt->data > pkt->size - 768) {
227            av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
228            return AVERROR_INVALIDDATA;
229        }
230        for (i = 0; i < 256; i++)
231            c->pal[i] = 0xFFU << 24 | bytestream_get_be24(&c->stream);
232    }
233    if (type & BMV_SCROLL) {
234        if (c->stream - pkt->data > pkt->size - 2) {
235            av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
236            return AVERROR_INVALIDDATA;
237        }
238        scr_off = (int16_t)bytestream_get_le16(&c->stream);
239    } else if ((type & BMV_INTRA) == BMV_INTRA) {
240        scr_off = -640;
241    } else {
242        scr_off = 0;
243    }
244
245    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
246        return ret;
247
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;
251    }
252
253    memcpy(frame->data[1], c->pal, AVPALETTE_SIZE);
254    frame->palette_has_changed = type & BMV_PALETTE;
255
256    outptr = frame->data[0];
257    srcptr = c->frame;
258
259    for (i = 0; i < avctx->height; i++) {
260        memcpy(outptr, srcptr, avctx->width);
261        srcptr += avctx->width;
262        outptr += frame->linesize[0];
263    }
264
265    *got_frame = 1;
266
267    /* always report that the buffer was completely consumed */
268    return pkt->size;
269}
270
271static av_cold int decode_init(AVCodecContext *avctx)
272{
273    BMVDecContext * const c = avctx->priv_data;
274
275    c->avctx = avctx;
276    avctx->pix_fmt = AV_PIX_FMT_PAL8;
277
278    if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) {
279        av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height);
280        return AVERROR_INVALIDDATA;
281    }
282
283    c->frame = c->frame_base + 640;
284
285    return 0;
286}
287
288const FFCodec ff_bmv_video_decoder = {
289    .p.name         = "bmv_video",
290    .p.long_name    = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
291    .p.type         = AVMEDIA_TYPE_VIDEO,
292    .p.id           = AV_CODEC_ID_BMV_VIDEO,
293    .priv_data_size = sizeof(BMVDecContext),
294    .init           = decode_init,
295    FF_CODEC_DECODE_CB(decode_frame),
296    .p.capabilities = AV_CODEC_CAP_DR1,
297    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
298};
299