From 70ce68d0212f7c1fd9b453fa203371dba05fb3af Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Fri, 13 Jun 2025 03:04:45 +0200 Subject: [PATCH] avcodec/mpegvideo: Don't reset AC values of upper-left luma block Said block will only be referenced by blocks from the same macroblock, which will read the new AC values instead of the reset values from this function. Signed-off-by: Andreas Rheinhardt --- libavcodec/mpegvideo.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c index a27efa8b89..b481d1eef4 100644 --- a/libavcodec/mpegvideo.c +++ b/libavcodec/mpegvideo.c @@ -506,7 +506,9 @@ void ff_clean_intra_table_entries(MpegEncContext *s) /* ac pred */ int16_t (*ac_val)[16] = s->ac_val[0]; av_assume(!((uintptr_t)ac_val & 0xF)); - memset(ac_val[xy ], 0, 2 * sizeof(*ac_val)); + // Don't reset the upper-left luma block, as it will only ever be + // referenced by blocks from the same macroblock. + memset(ac_val[xy + 1], 0, sizeof(*ac_val)); memset(ac_val[xy + wrap], 0, 2 * sizeof(*ac_val)); /* ac pred */ memset(ac_val[uxy], 0, sizeof(*ac_val));