/*
* Discworld II BMV video decoder
* Copyright (c) 2011 Konstantin Shishkov
*
* 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
*/
#include "libavutil/avassert.h"
#include "libavutil/common.h"
#include "avcodec.h"
#include "bytestream.h"
#include "internal.h"
enum BMVFlags{
BMV_NOP = 0,
BMV_END,
BMV_DELTA,
BMV_INTRA,
BMV_SCROLL = 0x04,
BMV_PALETTE = 0x08,
BMV_COMMAND = 0x10,
BMV_AUDIO = 0x20,
BMV_EXT = 0x40,
BMV_PRINT = 0x80
};
#define SCREEN_WIDE 640
#define SCREEN_HIGH 429
typedef struct BMVDecContext {
AVCodecContext *avctx;
uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)];
uint32_t pal[256];
const uint8_t *stream;
} BMVDecContext;
#define NEXT_BYTE(v) (v) = forward ? (v) + 1 : (v) - 1;
static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
{
unsigned val, saved_val = 0;
int tmplen = src_len;
const uint8_t *src, *source_end = source + src_len;
uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
uint8_t *dst, *dst_end;
int len, mask;
int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
int read_two_nibbles, flag;
int advance_mode;
int mode = 0;
int i;
if (src_len <= 0)
return AVERROR_INVALIDDATA;
if (forward) {
src = source;
dst = frame;
dst_end = frame_end;
} else {
src = source + src_len - 1;
dst = frame_end - 1;
dst_end = frame - 1;
}
for (;;) {
int shift = 0;
flag = 0;
/* The mode/len decoding is a bit strange:
* values are coded as variable-length codes with nibble units,
* code end is signalled by two top bits in the nibble being nonzero.
* And since data is bytepacked and we read two nibbles at a time,
* we may get a nibble belonging to the next code.
* Hence this convoluted loop.
*/
if (!mode || (tmplen == 4)) {
if (src < source || src >= source_end)
return AVERROR_INVALIDDATA;
val = *src;
read_two_nibbles = 1;
} else {
val = saved_val;
read_two_nibbles = 0;
}
if (!(val & 0xC)) {
for (;;) {
if(shift>22)
return -1;
if (!read_two_nibbles) {
if (src < source || src >= source_end)
return AVERROR_INVALIDDATA;
shift += 2;
val |= (unsigned)*src << shift;
if (*src & 0xC)
break;
}
// two upper bits of the nibble is zero,
// so shift top nibble value down into their place
read_two_nibbles = 0;
shift += 2;
mask = (1 << shift) - 1;
val = ((val >> 2) & ~mask) | (val & mask);
NEXT_BYTE(src);
if ((val & (0xC << shift))) {
flag = 1;
break;
}
}
} else if (mode) {
flag = tmplen != 4;
}
if (flag) {
tmplen = 4;
} else {
saved_val = val >> (4 + shift);
tmplen = 0;
val &= (1 << (shift + 4)) - 1;
NEXT_BYTE(src);
}
advance_mode = val & 1;
len = (val >> 1) - 1;
av_assert0(len>0);
mode += 1 + advance_mode;
if (mode >= 4)
mode -= 3;
if (len <= 0 || FFABS(dst_end - dst) < len)
return AVERROR_INVALIDDATA;
switch (mode) {
case 1:
if (forward) {
if (dst - frame + SCREEN_WIDE < frame_off ||
dst - frame + SCREEN_WIDE + frame_off < 0 ||
frame_end - dst < frame_off + len ||
frame_end - dst < len)
return AVERROR_INVALIDDATA;
for (i = 0; i < len; i++)
dst[i] = dst[frame_off + i];
dst += len;
} else {
dst -= len;
if (dst - frame + SCREEN_WIDE < frame_off ||
dst - frame + SCREEN_WIDE + frame_off < 0 ||
frame_end - dst < frame_off + len ||
frame_end - dst < len)
return AVERROR_INVALIDDATA;
for (i = len - 1; i >= 0; i--)
dst[i] = dst[frame_off + i];
}
break;
case 2:
if (forward) {
if (source + src_len - src < len)
return AVERROR_INVALIDDATA;
memcpy(dst, src, len);
dst += len;
src += len;
} else {
if (src - source < len)
return AVERROR_INVALIDDATA;
dst -= len;
src -= len;
memcpy(dst, src, len);
}
break;
case 3:
val = forward ? dst[-1] : dst[1];
if (forward) {
memset(dst, val, len);
dst += len;
} else {
dst -= len;
memset(dst, val, len);
}
break;
}
if (dst == dst_end)
return 0;
}
}
static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
AVPacket *pkt)
{
BMVDecContext * const c = avctx->priv_data;
AVFrame *frame = data;
int type, scr_off;
int i, ret;
uint8_t *srcptr, *outptr;
c->stream = pkt->data;
type = bytestream_get_byte(&c->stream);
if (type & BMV_AUDIO) {
int blobs = bytestream_get_byte(&c->stream);
if (pkt->size < blobs * 65 + 2) {
av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
c->stream += blobs * 65;
}
if (type & BMV_COMMAND) {
int command_size = (type & BMV_PRINT) ? 8 : 10;
if (c->stream - pkt->data + command_size > pkt->size) {
av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
c->stream += command_size;
}
if (type & BMV_PALETTE) {
if (c->stream - pkt->data > pkt->size - 768) {
av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
for (i = 0; i < 256; i++)
c->pal[i] = 0xFFU << 24 | bytestream_get_be24(&c->stream);
}
if (type & BMV_SCROLL) {
if (c->stream - pkt->data > pkt->size - 2) {
av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
scr_off = (int16_t)bytestream_get_le16(&c->stream);
} else if ((type & BMV_INTRA) == BMV_INTRA) {
scr_off = -640;
} else {
scr_off = 0;
}
if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
return ret;
if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
return AVERROR_INVALIDDATA;
}
memcpy(frame->data[1], c->pal, AVPALETTE_SIZE);
frame->palette_has_changed = type & BMV_PALETTE;
outptr = frame->data[0];
srcptr = c->frame;
for (i = 0; i < avctx->height; i++) {
memcpy(outptr, srcptr, avctx->width);
srcptr += avctx->width;
outptr += frame->linesize[0];
}
*got_frame = 1;
/* always report that the buffer was completely consumed */
return pkt->size;
}
static av_cold int decode_init(AVCodecContext *avctx)
{
BMVDecContext * const c = avctx->priv_data;
c->avctx = avctx;
avctx->pix_fmt = AV_PIX_FMT_PAL8;
if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) {
av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height);
return AVERROR_INVALIDDATA;
}
c->frame = c->frame_base + 640;
return 0;
}
AVCodec ff_bmv_video_decoder = {
.name = "bmv_video",
.long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
.type = AVMEDIA_TYPE_VIDEO,
.id = AV_CODEC_ID_BMV_VIDEO,
.priv_data_size = sizeof(BMVDecContext),
.init = decode_init,
.decode = decode_frame,
.capabilities = AV_CODEC_CAP_DR1,
.caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
};