From de0b97754756df349a8dc066816f3075f1afcc0f Mon Sep 17 00:00:00 2001
From: Gregory Maxwell <greg@xiph.org>
Date: Tue, 23 Aug 2011 02:00:55 -0400
Subject: [PATCH] In VBR the MDCT modes rate control could dramatically
over/undershoot after a frame size change because the adaptive rate control
offset was not being scaled.
---
libcelt/celt.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/libcelt/celt.c b/libcelt/celt.c
index 5131d3d3e..92f896a27 100644
--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -1382,8 +1382,9 @@ int celt_encode_with_ec(CELTEncoder * restrict st, const opus_val16 * pcm, int f
/* The target rate in 8th bits per frame */
opus_int32 target;
opus_int32 min_allowed;
+ int lm_diff = st->mode->maxLM - LM;
- target = vbr_rate + st->vbr_offset - ((40*C+20)<<BITRES);
+ target = vbr_rate + (st->vbr_offset>>lm_diff) - ((40*C+20)<<BITRES);
/* Shortblocks get a large boost in bitrate, but since they
are uncommon long blocks are not greatly affected */
@@ -1437,7 +1438,7 @@ int celt_encode_with_ec(CELTEncoder * restrict st, const opus_val16 * pcm, int f
/*printf ("%d\n", st->vbr_reservoir);*/
/* Compute the offset we need to apply in order to reach the target */
- st->vbr_drift += (opus_int32)MULT16_32_Q15(alpha,delta-st->vbr_offset-st->vbr_drift);
+ st->vbr_drift += (opus_int32)MULT16_32_Q15(alpha,(delta<<lm_diff)-st->vbr_offset-st->vbr_drift);
st->vbr_offset = -st->vbr_drift;
/*printf ("%d\n", st->vbr_drift);*/
--
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