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Adds "temporal VBR", which should be mostly useful at low bitrate.

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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.
This commit is contained in:
Jean-Marc Valin 2013-06-25 14:10:27 -04:00
parent b9176a4c3e
commit 3c0aa8fc25
1 changed files with 32 additions and 2 deletions
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34
celt/celt_encoder.c
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@ -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*/