ref: 87efe1df00c6f952e4121c103af787f755723b59
parent: 2ce5c63d224de2d5f7cf08363c5dbde8392a4d6d
author: Jean-Marc Valin <[email protected]>
date: Tue Jan 18 09:44:04 EST 2011
Adds an anti-collapse mechanism for transients This looks for bands in each short block that have no energy. For each of these "collapsed" bands, noise is injected to have an energy equal to the minimum of the two previous frames for that band. The mechanism can be used whenever there are 4 or more MDCTs (otherwise no complete collapse is possible) and is signalled with one bit just before the final fine energy bits.
--- a/libcelt/bands.c
+++ b/libcelt/bands.c
@@ -45,6 +45,11 @@
#include "mathops.h"
#include "rate.h"
+static celt_uint32 lcg_rand(celt_uint32 seed)
+{+ return 1664525 * seed + 1013904223;
+}
+
/* This is a cos() approximation designed to be bit-exact on any platform. Bit exactness
with this approximation is important because it has an impact on the bit allocation */
static celt_int16 bitexact_cos(celt_int16 x)
@@ -206,6 +211,74 @@
} while (++c<C);
}
+/* This prevents energy collapse for transients with multiple short MDCTs */
+void anti_collapse(const CELTMode *m, celt_norm *_X, int LM, int C, int size,
+ int start, int end, celt_word16 *logE, celt_word16 *prev1logE,
+ celt_word16 *prev2logE, int *pulses, celt_uint32 seed)
+{+ int c, i, j, k;
+ c=0; do
+ {+ for (i=start;i<end;i++)
+ {+ celt_norm *X;
+ int N0;
+ celt_word16 Ediff;
+ celt_word16 r;
+ celt_word16 thresh;
+ int depth;
+
+ N0 = m->eBands[i+1]-m->eBands[i];
+ Ediff = logE[c*m->nbEBands+i]-MIN16(prev1logE[c*m->nbEBands+i],prev2logE[c*m->nbEBands+i]);
+ Ediff = MAX16(0, Ediff);
+ depth = (1+(pulses[i]>>BITRES))/(m->eBands[i+1]-m->eBands[i]<<LM);
+
+#ifdef FIXED_POINT
+ thresh = MULT16_32_Q15(QCONST16(0.3f, 15), MIN32(32767,SHR32(celt_exp2(-SHL16(depth, 11)),1) ));
+ if (Ediff < 16384)
+ r = 2*MIN16(16383,SHR32(celt_exp2(-SHL16(Ediff, 11-DB_SHIFT)),1));
+ else
+ r = 0;
+ r = SHR16(MIN16(thresh, r),1);
+ {+ int shift;
+ celt_word32 t;
+ t = N0<<LM;
+ shift = celt_ilog2(t)>>1;
+ t = SHL32(t, (7-shift)<<1);
+ r = SHR32(MULT16_16_Q15(celt_rsqrt_norm(t), r),shift);
+ }
+#else
+ thresh = .3f*celt_exp2(-depth);
+ r = 2.f*celt_exp2(-Ediff);
+ r = MIN16(thresh, r);
+ r = r*celt_rsqrt(N0<<LM);
+#endif
+ X = _X+c*size+(m->eBands[i]<<LM);
+ for (k=0;k<1<<LM;k++)
+ {+ celt_word32 sum=0;
+ /* Detect collapse */
+ for (j=0;j<N0;j++)
+ sum += ABS16(X[(j<<LM)+k]);
+ if (sum<QCONST16(1e-4, 14))
+ {+ /* Fill with noise */
+ for (j=0;j<N0;j++)
+ {+ seed = lcg_rand(seed);
+ X[(j<<LM)+k] = (seed&0x8000 ? r : -r);
+ }
+ }
+ }
+ /* We just added some energy, so we need to renormalise */
+ renormalise_vector(X, N0<<LM, Q15ONE);
+ }
+ } while (++c<C);
+
+}
+
+
static void intensity_stereo(const CELTMode *m, celt_norm *X, celt_norm *Y, const celt_ener *bank, int bandID, int N)
{int i = bandID;
@@ -528,11 +601,6 @@
return qn;
}
-static celt_uint32 lcg_rand(celt_uint32 seed)
-{- return 1664525 * seed + 1013904223;
-}
-
/* This function is responsible for encoding and decoding a band for both
the mono and stereo case. Even in the mono case, it can split the band
in two and transmit the energy difference with the two half-bands. It
@@ -1054,7 +1122,7 @@
/* Compute how many bits we want to allocate to this band */
if (i != start)
balance -= tell;
- remaining_bits = ((celt_int32)total_bits<<BITRES)-tell-1;
+ remaining_bits = ((celt_int32)total_bits<<BITRES)-tell-1- (shortBlocks&&LM>=2 ? (1<<BITRES) : 0);
if (i <= codedBands-1)
{curr_balance = balance / IMIN(3, codedBands-i);
--- a/libcelt/bands.h
+++ b/libcelt/bands.h
@@ -93,4 +93,8 @@
void stereo_decision(const CELTMode *m, celt_norm * restrict X, int *stereo_mode, int len, int M);
+void anti_collapse(const CELTMode *m, celt_norm *_X, int LM, int C, int size,
+ int start, int end, celt_word16 *logE, celt_word16 *prev1logE,
+ celt_word16 *prev2logE, int *pulses, celt_uint32 seed);
+
#endif /* BANDS_H */
--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -96,6 +96,7 @@
celt_word16 prefilter_gain_old;
int prefilter_tapset_old;
#endif
+ int consec_transient;
/* VBR-related parameters */
celt_int32 vbr_reservoir;
@@ -113,7 +114,7 @@
celt_sig in_mem[1]; /* Size = channels*mode->overlap */
/* celt_sig prefilter_mem[], Size = channels*COMBFILTER_PERIOD */
/* celt_sig overlap_mem[], Size = channels*mode->overlap */
- /* celt_word16 oldEBands[], Size = channels*mode->nbEBands */
+ /* celt_word16 oldEBands[], Size = 2*channels*mode->nbEBands */
};
int celt_encoder_get_size(const CELTMode *mode, int channels)
@@ -121,7 +122,7 @@
int size = sizeof(struct CELTEncoder)
+ (2*channels*mode->overlap-1)*sizeof(celt_sig)
+ channels*COMBFILTER_MAXPERIOD*sizeof(celt_sig)
- + channels*mode->nbEBands*sizeof(celt_word16);
+ + 2*channels*mode->nbEBands*sizeof(celt_word16);
return size;
}
@@ -784,6 +785,7 @@
VARDECL(celt_norm, X);
VARDECL(celt_ener, bandE);
VARDECL(celt_word16, bandLogE);
+ VARDECL(celt_word16, oldLogE);
VARDECL(int, fine_quant);
VARDECL(celt_word16, error);
VARDECL(int, pulses);
@@ -792,7 +794,7 @@
VARDECL(int, tf_res);
celt_sig *_overlap_mem;
celt_sig *prefilter_mem;
- celt_word16 *oldBandE;
+ celt_word16 *oldBandE, *oldLogE2;
int shortBlocks=0;
int isTransient=0;
int resynth;
@@ -817,6 +819,7 @@
celt_int32 tell;
int prefilter_tapset=0;
int pf_on;
+ int anti_collapse_on=0;
SAVE_STACK;
if (nbCompressedBytes<0 || pcm==NULL)
@@ -833,6 +836,7 @@
_overlap_mem = prefilter_mem+C*COMBFILTER_MAXPERIOD;
/*_overlap_mem = st->in_mem+C*(st->overlap);*/
oldBandE = (celt_word16*)(st->in_mem+C*(2*st->overlap+COMBFILTER_MAXPERIOD));
+ oldLogE2 = oldBandE + C*st->mode->nbEBands;
if (enc==NULL)
{@@ -1059,6 +1063,9 @@
for (i=effEnd;i<st->end;i++)
tf_res[i] = tf_res[effEnd-1];
+ ALLOC(oldLogE, C*st->mode->nbEBands, celt_word16);
+ for (i=0;i<C*st->mode->nbEBands;i++)
+ oldLogE[i] = oldBandE[i];
ALLOC(error, C*st->mode->nbEBands, celt_word16);
quant_coarse_energy(st->mode, st->start, st->end, effEnd, bandLogE,
oldBandE, total_bits, error, enc,
@@ -1258,8 +1265,8 @@
ALLOC(pulses, st->mode->nbEBands, int);
ALLOC(fine_priority, st->mode->nbEBands, int);
- /* bits = packet size - where we are - safety */
- bits = (nbCompressedBytes*8<<BITRES) - ec_enc_tell(enc, BITRES) - 1;
+ /* bits = packet size - where we are - safety - anti-collapse*/
+ bits = (nbCompressedBytes*8<<BITRES) - ec_enc_tell(enc, BITRES) - 1 - (isTransient&&LM>=2 ? (1<<BITRES) : 0);
codedBands = compute_allocation(st->mode, st->start, st->end, offsets,
alloc_trim, &intensity, &dual_stereo, bits, pulses, fine_quant,
fine_priority, C, LM, enc, 1, st->lastCodedBands);
@@ -1283,6 +1290,11 @@
bandE, pulses, shortBlocks, st->spread_decision, dual_stereo, intensity, tf_res, resynth,
nbCompressedBytes*8, enc, LM, codedBands);
+ if (isTransient && LM>=2)
+ {+ anti_collapse_on = st->consec_transient<2;
+ ec_enc_bits(enc, anti_collapse_on, 1);
+ }
quant_energy_finalise(st->mode, st->start, st->end, bandE, oldBandE, error, fine_quant, fine_priority, nbCompressedBytes*8-ec_enc_tell(enc, 0), enc, C);
#ifdef RESYNTH
@@ -1297,6 +1309,11 @@
#ifdef MEASURE_NORM_MSE
measure_norm_mse(st->mode, X, X0, bandE, bandE0, M, N, C);
#endif
+ if (anti_collapse_on)
+ {+ anti_collapse(st->mode, X, LM, C, N,
+ st->start, st->end, oldBandE, oldLogE, oldLogE2, pulses, enc->rng);
+ }
/* Synthesis */
denormalise_bands(st->mode, X, freq, bandE, effEnd, C, M);
@@ -1360,6 +1377,12 @@
oldBandE[i]=0;
for (i=st->end;i<st->mode->nbEBands;i++)
oldBandE[i]=0;
+ for (i=0;i<C*st->mode->nbEBands;i++)
+ oldLogE2[i] = oldLogE[i];
+ if (isTransient)
+ st->consec_transient++;
+ else
+ st->consec_transient=0;
/* If there's any room left (can only happen for very high rates),
fill it with zeros */
@@ -1585,7 +1608,7 @@
celt_sig _decode_mem[1]; /* Size = channels*(DECODE_BUFFER_SIZE+mode->overlap) */
/* celt_word16 lpc[], Size = channels*LPC_ORDER */
- /* celt_word16 oldEBands[], Size = channels*mode->nbEBands */
+ /* celt_word16 oldEBands[], Size = 2*channels*mode->nbEBands */
};
int celt_decoder_get_size(const CELTMode *mode, int channels)
@@ -1593,7 +1616,7 @@
int size = sizeof(struct CELTDecoder)
+ (channels*(DECODE_BUFFER_SIZE+mode->overlap)-1)*sizeof(celt_sig)
+ channels*LPC_ORDER*sizeof(celt_word16)
- + channels*mode->nbEBands*sizeof(celt_word16);
+ + 2*channels*mode->nbEBands*sizeof(celt_word16);
return size;
}
@@ -1853,6 +1876,7 @@
VARDECL(celt_sig, freq);
VARDECL(celt_norm, X);
VARDECL(celt_ener, bandE);
+ VARDECL(celt_word16, oldLogE);
VARDECL(int, fine_quant);
VARDECL(int, pulses);
VARDECL(int, offsets);
@@ -1863,7 +1887,7 @@
celt_sig *overlap_mem[2];
celt_sig *out_syn[2];
celt_word16 *lpc;
- celt_word16 *oldBandE;
+ celt_word16 *oldBandE, *oldLogE2;
int shortBlocks;
int isTransient;
@@ -1881,6 +1905,7 @@
celt_int32 tell;
int dynalloc_logp;
int postfilter_tapset;
+ int anti_collapse_on=0;
SAVE_STACK;
if (pcm==NULL)
@@ -1900,6 +1925,7 @@
} while (++c<C);
lpc = (celt_word16*)(st->_decode_mem+(DECODE_BUFFER_SIZE+st->overlap)*C);
oldBandE = lpc+C*LPC_ORDER;
+ oldLogE2 = oldBandE + C*st->mode->nbEBands;
N = M*st->mode->shortMdctSize;
@@ -1976,6 +2002,10 @@
else
shortBlocks = 0;
+ ALLOC(oldLogE, C*st->mode->nbEBands, celt_word16);
+ for (i=0;i<C*st->mode->nbEBands;i++)
+ oldLogE[i] = oldBandE[i];
+
/* Decode the global flags (first symbols in the stream) */
intra_ener = tell+3<=total_bits ? ec_dec_bit_logp(dec, 3) : 0;
/* Get band energies */
@@ -2030,7 +2060,7 @@
alloc_trim = tell+(6<<BITRES) <= total_bits ?
ec_dec_icdf(dec, trim_icdf, 7) : 5;
- bits = (len*8<<BITRES) - ec_dec_tell(dec, BITRES) - 1;
+ bits = (len*8<<BITRES) - ec_dec_tell(dec, BITRES) - 1 - (isTransient&&LM>=2 ? (1<<BITRES) : 0);
codedBands = compute_allocation(st->mode, st->start, st->end, offsets,
alloc_trim, &intensity, &dual_stereo, bits, pulses, fine_quant,
fine_priority, C, LM, dec, 0, 0);
@@ -2042,9 +2072,18 @@
NULL, pulses, shortBlocks, spread_decision, dual_stereo, intensity, tf_res, 1,
len*8, dec, LM, codedBands);
+ if (isTransient && LM>=2)
+ {+ anti_collapse_on = ec_dec_bits(dec, 1);
+ }
+
unquant_energy_finalise(st->mode, st->start, st->end, bandE, oldBandE,
fine_quant, fine_priority, len*8-ec_dec_tell(dec, 0), dec, C);
+ if (anti_collapse_on)
+ anti_collapse(st->mode, X, LM, C, N,
+ st->start, st->end, oldBandE, oldLogE, oldLogE2, pulses, dec->rng);
+
log2Amp(st->mode, st->start, st->end, bandE, oldBandE, C);
/* Synthesis */
@@ -2101,6 +2140,8 @@
oldBandE[i]=0;
for (i=st->end;i<st->mode->nbEBands;i++)
oldBandE[i]=0;
+ for (i=0;i<C*st->mode->nbEBands;i++)
+ oldLogE2[i] = oldLogE[i];
deemphasis(out_syn, pcm, N, C, st->mode->preemph, st->preemph_memD);
st->loss_count = 0;