From d2c484b5e76f0d02b804b81e30672efa771081da Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Mon, 6 May 2013 16:02:31 -0400
Subject: [PATCH] Adds spreading to the surround masking computation
This avoids a single low-energy band from changing the masking results.
---
celt/celt_encoder.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/celt/celt_encoder.c b/celt/celt_encoder.c
index 2030ad08e..66de1ba24 100644
--- a/celt/celt_encoder.c
+++ b/celt/celt_encoder.c
@@ -1411,13 +1411,23 @@ int celt_encode_with_ec(CELTEncoder * OPUS_RESTRICT st, const opus_val16 * pcm,
st->energy_save[i]=bandLogE[i]-offset;
st->energy_save=NULL;
}
+ /* This computes how much masking takes place between surround channels */
if (st->energy_mask&&!st->lfe)
{
opus_val32 mask_avg=0;
opus_val16 offset = shortBlocks?HALF16(SHL16(LM, DB_SHIFT)):0;
for (c=0;c<C;c++)
+ {
+ opus_val16 followE, followMask;
+ followE = followMask = -QCONST16(14.f, DB_SHIFT);
for(i=0;i<st->end;i++)
- mask_avg += bandLogE[nbEBands*c+i]-offset-st->energy_mask[nbEBands*c+i];
+ {
+ /* We use a simple follower to approximate the masking spreading function. */
+ followE = MAX16(followE-QCONST16(1.f, DB_SHIFT), bandLogE[nbEBands*c+i]-offset);
+ followMask = MAX16(followMask-QCONST16(1.f, DB_SHIFT), st->energy_mask[nbEBands*c+i]);
+ mask_avg += followE-followMask;
+ }
+ }
surround_masking = DIV32_16(mask_avg,C*st->end) + QCONST16(.0f, DB_SHIFT);
surround_masking = MIN16(MAX16(surround_masking,-QCONST16(1.5f, DB_SHIFT)), 0);
}
--
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