From 3c0aa8fc252c44b40a0e0247aa744b1302c9a2fb Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Tue, 25 Jun 2013 14:10:27 -0400
Subject: [PATCH] Adds "temporal VBR", which should be mostly useful at low
bitrate.
The idea is to allow more noise than the default in quiet segments.
Right now, this hurts for high bitrates , so it's gradually reduced
as the rate goes up, until it's completely disabled above 68 kb/s.
---
celt/celt_encoder.c | 34 ++++++++++++++++++++++++++++++++--
1 file changed, 32 insertions(+), 2 deletions(-)
diff --git a/celt/celt_encoder.c b/celt/celt_encoder.c
index fb3e3cef0..a3439a460 100644
--- a/celt/celt_encoder.c
+++ b/celt/celt_encoder.c
@@ -113,6 +113,7 @@ struct OpusCustomEncoder {
int intensity;
opus_val16 *energy_save;
opus_val16 *energy_mask;
+ opus_val16 spec_avg;
#ifdef RESYNTH
/* +MAX_PERIOD/2 to make space for overlap */
@@ -1115,7 +1116,8 @@ static int compute_vbr(const CELTMode *mode, AnalysisInfo *analysis, opus_int32
int LM, opus_int32 bitrate, int lastCodedBands, int C, int intensity,
int constrained_vbr, opus_val16 stereo_saving, int tot_boost,
opus_val16 tf_estimate, int pitch_change, opus_val16 maxDepth,
- int variable_duration, int lfe, int has_surround_mask, opus_val16 surround_masking)
+ int variable_duration, int lfe, int has_surround_mask, opus_val16 surround_masking,
+ opus_val16 temporal_vbr)
{
/* The target rate in 8th bits per frame */
opus_int32 target;
@@ -1208,6 +1210,16 @@ static int compute_vbr(const CELTMode *mode, AnalysisInfo *analysis, opus_int32
target = base_target + (opus_int32)MULT16_32_Q15(rate_factor, target-base_target);
}
+
+ if (tf_estimate < QCONST16(.2f, 14))
+ {
+ opus_val16 amount;
+ opus_val16 tvbr_factor;
+ amount = MULT16_16_Q15(QCONST16(.000006f, 30), IMAX(0, IMIN(42000, 68000-bitrate)));
+ tvbr_factor = SHR32(MULT16_16(temporal_vbr, amount), DB_SHIFT);
+ target += (opus_int32)MULT16_32_Q15(tvbr_factor, target);
+ }
+
/* Don't allow more than doubling the rate */
target = IMIN(2*base_target, target);
@@ -1275,6 +1287,7 @@ int celt_encode_with_ec(CELTEncoder * OPUS_RESTRICT st, const opus_val16 * pcm,
int signalBandwidth;
int transient_got_disabled=0;
opus_val16 surround_masking=0;
+ opus_val16 temporal_vbr=0;
ALLOC_STACK;
mode = st->mode;
@@ -1538,6 +1551,22 @@ int celt_encode_with_ec(CELTEncoder * OPUS_RESTRICT st, const opus_val16 * pcm,
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);
}
+ {
+ opus_val16 follow=-QCONST16(10.0f,DB_SHIFT);
+ float frame_avg=0;
+ opus_val16 offset = shortBlocks?HALF16(SHL16(LM, DB_SHIFT)):0;
+ for(i=st->start;i<st->end;i++)
+ {
+ follow = MAX16(follow-QCONST16(1.f, DB_SHIFT), bandLogE[i]-offset);
+ if (C==2)
+ follow = MAX16(follow, bandLogE[i+nbEBands]-offset);
+ frame_avg += follow;
+ }
+ frame_avg /= (st->end-st->start);
+ temporal_vbr = SUB16(frame_avg,st->spec_avg);
+ temporal_vbr = MIN16(QCONST16(3.f, DB_SHIFT), MAX16(-QCONST16(1.5f, DB_SHIFT), temporal_vbr));
+ st->spec_avg += MULT16_16_Q15(QCONST16(.02f, 15), temporal_vbr);
+ }
/*for (i=0;i<21;i++)
printf("%f ", bandLogE[i]);
printf("\n");*/
@@ -1744,7 +1773,8 @@ int celt_encode_with_ec(CELTEncoder * OPUS_RESTRICT st, const opus_val16 * pcm,
target = compute_vbr(mode, &st->analysis, base_target, LM, st->bitrate,
st->lastCodedBands, C, st->intensity, st->constrained_vbr,
st->stereo_saving, tot_boost, tf_estimate, pitch_change, maxDepth,
- st->variable_duration, st->lfe, st->energy_mask!=NULL, surround_masking);
+ st->variable_duration, st->lfe, st->energy_mask!=NULL, surround_masking,
+ temporal_vbr);
/* The current offset is removed from the target and the space used
so far is added*/
--
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