From 05c6eca4db7f2abec32c9ce0fc325d9a0b933fb7 Mon Sep 17 00:00:00 2001
From: "Timothy B. Terriberry" <tterribe@xiph.org>
Date: Thu, 10 Jun 2010 18:42:24 -0400
Subject: [PATCH] Fix new MV clamping scheme for chroma MVs.
The new scheme introduced in I68d35a2f did not clamp chroma MVs in the SPLITMV
case, and clamped them incorrectly (to the luma plane bounds) in every other
case.
Because chroma MVs are computed from the luma MVs before clamping occurs, they
could still point outside of the frame buffer and cause crashes.
This clamping happens outside of the MV prediction loop, and so should not
affect bitstream decoding.
---
vp8/decoder/decodframe.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/vp8/decoder/decodframe.c b/vp8/decoder/decodframe.c
index de4a645883..04fb03fa4d 100644
--- a/vp8/decoder/decodframe.c
+++ b/vp8/decoder/decodframe.c
@@ -149,6 +149,19 @@ static void clamp_mv_to_umv_border(MV *mv, const MACROBLOCKD *xd)
mv->row = xd->mb_to_bottom_edge + (16 << 3);
}
+/* A version of the above function for chroma block MVs.*/
+static void clamp_uvmv_to_umv_border(MV *mv, const MACROBLOCKD *xd)
+{
+ if (2*mv->col < (xd->mb_to_left_edge - (19 << 3)))
+ mv->col = (xd->mb_to_left_edge - (16 << 3)) >> 1;
+ else if (2*mv->col > xd->mb_to_right_edge + (18 << 3))
+ mv->col = (xd->mb_to_right_edge + (16 << 3)) >> 1;
+
+ if (2*mv->row < (xd->mb_to_top_edge - (19 << 3)))
+ mv->row = (xd->mb_to_top_edge - (16 << 3)) >> 1;
+ else if (2*mv->row > xd->mb_to_bottom_edge + (18 << 3))
+ mv->row = (xd->mb_to_bottom_edge + (16 << 3)) >> 1;
+}
static void clamp_mvs(MACROBLOCKD *xd)
{
@@ -158,11 +171,13 @@ static void clamp_mvs(MACROBLOCKD *xd)
for (i=0; i<16; i++)
clamp_mv_to_umv_border(&xd->block[i].bmi.mv.as_mv, xd);
+ for (i=16; i<24; i++)
+ clamp_uvmv_to_umv_border(&xd->block[i].bmi.mv.as_mv, xd);
}
else
{
clamp_mv_to_umv_border(&xd->mbmi.mv.as_mv, xd);
- clamp_mv_to_umv_border(&xd->block[16].bmi.mv.as_mv, xd);
+ clamp_uvmv_to_umv_border(&xd->block[16].bmi.mv.as_mv, xd);
}
}
--
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