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avcodec/sanm: codec23 decoder

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This codec alternatingly skips and changes existing pixels.
A second 16bit parameter in the FOBJ header indicates how to do
the pixel changes: either by specifying a LUT in the codec datastream
or by adding a constant value to the pixel.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
This commit is contained in:
Manuel Lauss
2025-03-11 13:35:33 +01:00
parent 968ffbe64a
commit 77b5a0c134
1 changed files with 64 additions and 2 deletions
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66
libavcodec/sanm.c
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@ -292,6 +292,7 @@ typedef struct SANMVideoContext {
int8_t p4x4glyphs[NGLYPHS][16];
int8_t p8x8glyphs[NGLYPHS][64];
uint8_t c47itbl[0x10000];
uint8_t c23lut[256];
} SANMVideoContext;
typedef struct SANMFrameHeader {
@ -557,6 +558,62 @@ static int rle_decode(SANMVideoContext *ctx, uint8_t *dst, const int out_size)
return 0;
}
static int old_codec23(SANMVideoContext *ctx, int top, int left, int width,
int height, uint8_t param, uint16_t param2)
{
const uint32_t maxpxo = ctx->height * ctx->pitch;
uint8_t *dst, lut[256], c;
int i, j, k, pc, sk;
int32_t pxoff;
if (ctx->subversion < 2) {
/* Rebel Assault 1: constant offset + 0xd0 */
for (i = 0; i < 256; i++)
lut[i] = (i + param + 0xd0) & 0xff;
} else if (param2 == 256) {
if (bytestream2_get_bytes_left(&ctx->gb) < 256)
return AVERROR_INVALIDDATA;
bytestream2_get_bufferu(&ctx->gb, ctx->c23lut, 256);
} else if (param2 < 256) {
for (i = 0; i < 256; i++)
lut[i] = (i + param2) & 0xff;
} else {
memcpy(lut, ctx->c23lut, 256);
}
if (bytestream2_get_bytes_left(&ctx->gb) < 1)
return 0; /* some c23 frames just set up the LUT */
dst = (uint8_t *)ctx->frm0;
for (i = 0; i < height; i++) {
if (bytestream2_get_bytes_left(&ctx->gb) < 2)
return 0;
pxoff = left + ((top + i) * ctx->pitch);
k = bytestream2_get_le16u(&ctx->gb);
sk = 1;
pc = 0;
while (k > 0 && pc <= width) {
if (bytestream2_get_bytes_left(&ctx->gb) < 1)
return AVERROR_INVALIDDATA;
j = bytestream2_get_byteu(&ctx->gb);
if (sk) {
pxoff += j;
pc += j;
} else {
while (j--) {
if (pxoff >=0 && pxoff < maxpxo) {
c = *(dst + pxoff);
*(dst + pxoff) = lut[c];
}
pxoff++;
pc++;
}
}
sk ^= 1;
}
}
return 0;
}
static int old_codec1(SANMVideoContext *ctx, int top,
int left, int width, int height, int opaque)
{
@ -1258,11 +1315,15 @@ static int old_codec48(SANMVideoContext *ctx, int width, int height)
static int process_frame_obj(SANMVideoContext *ctx)
{
uint16_t codec = bytestream2_get_le16u(&ctx->gb);
uint16_t parm2;
uint8_t codec = bytestream2_get_byteu(&ctx->gb);
uint8_t param = bytestream2_get_byteu(&ctx->gb);
int16_t left = bytestream2_get_le16u(&ctx->gb);
int16_t top = bytestream2_get_le16u(&ctx->gb);
uint16_t w = bytestream2_get_le16u(&ctx->gb);
uint16_t h = bytestream2_get_le16u(&ctx->gb);
bytestream2_skip(&ctx->gb, 2);
parm2 = bytestream2_get_le16u(&ctx->gb);
if (w < 1 || h < 1 || w > 800 || h > 600 || left > 800 || top > 600) {
av_log(ctx->avctx, AV_LOG_WARNING,
@ -1316,7 +1377,6 @@ static int process_frame_obj(SANMVideoContext *ctx)
h = ctx->height;
}
}
bytestream2_skip(&ctx->gb, 4);
/* on first FOBJ, when the codec is not one of the
* full-buffer codecs (37/47/48), frm0 needs to be cleared.
@ -1333,6 +1393,8 @@ static int process_frame_obj(SANMVideoContext *ctx)
return old_codec1(ctx, top, left, w, h, codec == 3);
case 2:
return old_codec2(ctx, top, left, w, h);
case 23:
return old_codec23(ctx, top, left, w, h, param, parm2);
case 37:
return old_codec37(ctx, w, h);
case 47: