From: Niklas Haas <g...@haasn.dev>
This bug flew under the radar because, in practice, these values are
0-initialized for the first invocation. But for subsequent invocations
(with different h/v values), reading from the uninitialized parts of
`out` is undefined behavior.
Avoid this by simply adjusting the iteration range of the next loop. Has
the added benefit of being a minor speedup.
---
libavcodec/h274.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/libavcodec/h274.c b/libavcodec/h274.c
index 5e2cf150ea..a59d09b66e 100644
--- a/libavcodec/h274.c
+++ b/libavcodec/h274.c
@@ -74,12 +74,14 @@ static void init_slice_c(int8_t out[64][64], uint8_t h,
uint8_t v,
// 64x64 inverse integer transform
for (int y = 0; y < 64; y++) {
- for (int x = 0; x < 64; x++) {
+ for (int x = 0; x <= freq_h; x++) {
int32_t sum = 0;
- for (int p = 0; p < 64; p++)
+ for (int p = 0; p <= freq_v; p++)
sum += R64T[y][p] * out[x][p];
tmp[y][x] = (sum + 128) >> 8;
}
+ for (int x = freq_h+1; x < 64; x++)
+ tmp[y][x] = 0;
}
for (int y = 0; y < 64; y++) {
--
2.33.0
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