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avcodec/sanm: codec21 decoder

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similar to codec23, this one alternatingly skips and writes bytes.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
This commit is contained in:
Manuel Lauss
2025-03-11 13:55:51 +01:00
parent 77b5a0c134
commit e1fd6bc8b4
1 changed files with 45 additions and 0 deletions
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45
libavcodec/sanm.c
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@ -614,6 +614,49 @@ static int old_codec23(SANMVideoContext *ctx, int top, int left, int width,
return 0;
}
static int old_codec21(SANMVideoContext *ctx, int top, int left, int width,
int height)
{
const uint32_t maxpxo = ctx->height * ctx->pitch;
uint8_t *dst = (uint8_t *)ctx->frm0, c;
int i, j, k, pc, sk, pxoff;
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) < 2)
return AVERROR_INVALIDDATA;
j = bytestream2_get_le16u(&ctx->gb);
k -= 2;
if (sk) {
pxoff += j;
pc += j;
} else {
if (bytestream2_get_bytes_left(&ctx->gb) < (j + 1))
return AVERROR_INVALIDDATA;
do {
c = bytestream2_get_byteu(&ctx->gb);
if (pxoff >=0 && pxoff < maxpxo) {
*(dst + pxoff) = c;
}
pxoff++;
pc++;
j--;
k--;
} while (j > -1);
}
sk ^= 1;
}
}
return 0;
}
static int old_codec1(SANMVideoContext *ctx, int top,
int left, int width, int height, int opaque)
{
@ -1393,6 +1436,8 @@ 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 21:
return old_codec21(ctx, top, left, w, h);
case 23:
return old_codec23(ctx, top, left, w, h, param, parm2);
case 37: