From 78ecbc98e4df70e94e8f2029c8d2d65f643e6f74 Mon Sep 17 00:00:00 2001
From: Deb Mukherjee <debargha@google.com>
Date: Wed, 28 Mar 2012 15:19:45 -0700
Subject: [PATCH] Bug fix in probability update savings computation
Found this bug while tracking down some anomalies in my experiments.
Since vp8_cost_one and vp8_cost_zero return unsigned int, the
bit shift by 8 will be incorrect if the value is negative.
I am cautiously optimistic that this fix will make the prob
updates more correct and somewhat improve results across the board.
But the update probabilities will need to be retuned I think.
Patch 2: Adding more of the same fixes using a macro.
Change-Id: I1a168f040e74e8c67e7225103b1c2af9a611da49
---
vp8/encoder/bitstream.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/vp8/encoder/bitstream.c b/vp8/encoder/bitstream.c
index b698618a6f..7288ead680 100644
--- a/vp8/encoder/bitstream.c
+++ b/vp8/encoder/bitstream.c
@@ -44,6 +44,8 @@ extern unsigned int active_section;
int count_mb_seg[4] = { 0, 0, 0, 0 };
#endif
+#define vp8_cost_upd ((int)(vp8_cost_one(upd) - vp8_cost_zero(upd)) >> 8)
+
static void update_mode(
vp8_writer *const w,
int n,
@@ -157,8 +159,7 @@ static int prob_update_savings(const unsigned int *ct,
{
const int old_b = vp8_cost_branch(ct, oldp);
const int new_b = vp8_cost_branch(ct, newp);
- const int update_b = 8 +
- ((vp8_cost_one(upd) - vp8_cost_zero(upd)) >> 8);
+ const int update_b = 8 + vp8_cost_upd;
return old_b - new_b - update_b;
}
@@ -1330,8 +1331,7 @@ int vp8_estimate_entropy_savings(VP8_COMP *cpi)
const int old_b = vp8_cost_branch(ct, old);
const int new_b = vp8_cost_branch(ct, newp);
- const int update_b = 8 +
- ((vp8_cost_one(upd) - vp8_cost_zero(upd)) >> 8);
+ const int update_b = 8 + vp8_cost_upd;
const int s = old_b - new_b - update_b;
@@ -1519,8 +1519,7 @@ static void update_coef_probs(VP8_COMP *cpi)
const vp8_prob upd = vp8_coef_update_probs_8x8 [i][j][k][t];
const int old_b = vp8_cost_branch(ct, old);
const int new_b = vp8_cost_branch(ct, newp);
- const int update_b = 8 +
- ((vp8_cost_one(upd) - vp8_cost_zero(upd)) >> 8);
+ const int update_b = 8 + vp8_cost_upd;
const int s = old_b - new_b - update_b;
const int u = s > 0 ? 1 : 0;
@@ -1586,8 +1585,7 @@ static void update_coef_probs(VP8_COMP *cpi)
const vp8_prob upd = vp8_coef_update_probs_8x8 [i][j][k][t];
const int old_b = vp8_cost_branch(ct, old);
const int new_b = vp8_cost_branch(ct, newp);
- const int update_b = 8 +
- ((vp8_cost_one(upd) - vp8_cost_zero(upd)) >> 8);
+ const int update_b = 8 + vp8_cost_upd;
const int s = old_b - new_b - update_b;
const int u = s > 0 ? 1 : 0;
vp8_write(w, u, upd);
--
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