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Code Issues Releases Activity

avcodec/sanm: codec47: read the small codebook

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codec47 carries a 4-byte small codebook in its header. Read those
4 bytes into context member instead of awkwardly redirecting the
bytestream pointer every time it needs to be accessed.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
This commit is contained in:
Manuel Lauss
2025-08-26 22:11:44 +02:00
parent 72e6206c88
commit f98cd66b4b
1 changed files with 10 additions and 14 deletions
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24
libavcodec/sanm.c
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@@ -296,6 +296,7 @@ typedef struct SANMVideoContext {
uint8_t c23lut[256];
uint8_t c4tbl[2][256][16];
uint16_t c4param;
uint8_t c47cb[4];
} SANMVideoContext;
typedef struct SANMFrameHeader {
@@ -1230,7 +1231,7 @@ static int old_codec37(SANMVideoContext *ctx, int width, int height)
}
static int process_block(SANMVideoContext *ctx, uint8_t *dst, uint8_t *prev1,
uint8_t *prev2, int stride, int tbl, int size)
uint8_t *prev2, int stride, int size)
{
int code, k, t;
uint8_t colors[2];
@@ -1252,18 +1253,18 @@ static int process_block(SANMVideoContext *ctx, uint8_t *dst, uint8_t *prev1,
dst[1 + stride] = bytestream2_get_byteu(&ctx->gb);
} else {
size >>= 1;
if (process_block(ctx, dst, prev1, prev2, stride, tbl, size))
if (process_block(ctx, dst, prev1, prev2, stride, size))
return AVERROR_INVALIDDATA;
if (process_block(ctx, dst + size, prev1 + size, prev2 + size,
stride, tbl, size))
stride, size))
return AVERROR_INVALIDDATA;
dst += size * stride;
prev1 += size * stride;
prev2 += size * stride;
if (process_block(ctx, dst, prev1, prev2, stride, tbl, size))
if (process_block(ctx, dst, prev1, prev2, stride, size))
return AVERROR_INVALIDDATA;
if (process_block(ctx, dst + size, prev1 + size, prev2 + size,
stride, tbl, size))
stride, size))
return AVERROR_INVALIDDATA;
}
break;
@@ -1292,12 +1293,8 @@ static int process_block(SANMVideoContext *ctx, uint8_t *dst, uint8_t *prev1,
memcpy(dst + k * stride, prev1 + k * stride, size);
break;
default:
k = bytestream2_tell(&ctx->gb);
bytestream2_seek(&ctx->gb, tbl + (code & 7), SEEK_SET);
t = bytestream2_get_byte(&ctx->gb);
bytestream2_seek(&ctx->gb, k, SEEK_SET);
for (k = 0; k < size; k++)
memset(dst + k * stride, t, size);
memset(dst + k * stride, ctx->c47cb[code & 3], size);
}
} else {
int mx = motion_vectors[code][0];
@@ -1377,13 +1374,13 @@ static int old_codec47(SANMVideoContext *ctx, int width, int height)
uint8_t *prev1 = (uint8_t *)ctx->frm1;
uint8_t *prev2 = (uint8_t *)ctx->frm2;
uint8_t auxcol[2];
int tbl_pos = bytestream2_tell(&ctx->gb);
int seq = bytestream2_get_le16(&ctx->gb);
int compr = bytestream2_get_byte(&ctx->gb);
int new_rot = bytestream2_get_byte(&ctx->gb);
int skip = bytestream2_get_byte(&ctx->gb);
bytestream2_skip(&ctx->gb, 7);
bytestream2_skip(&ctx->gb, 3);
bytestream2_get_bufferu(&ctx->gb, ctx->c47cb, 4);
auxcol[0] = bytestream2_get_byteu(&ctx->gb);
auxcol[1] = bytestream2_get_byteu(&ctx->gb);
decoded_size = bytestream2_get_le32(&ctx->gb);
@@ -1423,8 +1420,7 @@ static int old_codec47(SANMVideoContext *ctx, int width, int height)
if (seq == ctx->prev_seq + 1) {
for (j = 0; j < height; j += 8) {
for (i = 0; i < width; i += 8)
if (process_block(ctx, dst + i, prev1 + i, prev2 + i, stride,
tbl_pos + 8, 8))
if (process_block(ctx, dst + i, prev1 + i, prev2 + i, stride, 8))
return AVERROR_INVALIDDATA;
dst += stride * 8;
prev1 += stride * 8;