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Improved quality of small frame sizes at low bitrate.

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Adding a temporal energy floor to prevent extremely small values when there's
only one bin in the band.
This commit is contained in:
Jean-Marc Valin 2010-06-23 15:22:54 -04:00
parent 281c8b7e99
commit a01106587c
3 changed files with 16 additions and 3 deletions
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9
libcelt/celt.c
View file

@ -717,6 +717,7 @@ int celt_encode_with_ec_float(CELTEncoder * restrict st, const celt_sig * pcm, c
int LM, M; int LM, M;
int tf_select; int tf_select;
celt_int32 vbr_rate=0; celt_int32 vbr_rate=0;
celt_word16 max_decay;
int nbFilledBytes, nbAvailableBytes; int nbFilledBytes, nbAvailableBytes;
SAVE_STACK; SAVE_STACK;
@ -952,7 +953,13 @@ int celt_encode_with_ec_float(CELTEncoder * restrict st, const celt_sig * pcm, c
/* Bit allocation */ /* Bit allocation */
ALLOC(error, C*st->mode->nbEBands, celt_word16); ALLOC(error, C*st->mode->nbEBands, celt_word16);
coarse_needed = quant_coarse_energy(st->mode, st->start, bandLogE, st->oldBandE, nbAvailableBytes*4-8, intra_ener, st->mode->prob, error, enc, C);
#ifdef FIXED_POINT
max_decay = MIN32(QCONST16(16,DB_SHIFT), SHL32(EXTEND32(nbAvailableBytes),DB_SHIFT-3));
#else
max_decay = .125*nbAvailableBytes;
#endif
coarse_needed = quant_coarse_energy(st->mode, st->start, bandLogE, st->oldBandE, nbAvailableBytes*4-8, intra_ener, st->mode->prob, error, enc, C, max_decay);
coarse_needed = ((coarse_needed*3-1)>>3)+1; coarse_needed = ((coarse_needed*3-1)>>3)+1;
if (coarse_needed > nbAvailableBytes) if (coarse_needed > nbAvailableBytes)
coarse_needed = nbAvailableBytes; coarse_needed = nbAvailableBytes;

8
libcelt/quant_bands.c
View file

@ -84,7 +84,7 @@ void quant_prob_free(int *freq)
celt_free(freq); celt_free(freq);
} }
unsigned quant_coarse_energy(const CELTMode *m, int start, celt_word16 *eBands, celt_word16 *oldEBands, int budget, int intra, int *prob, celt_word16 *error, ec_enc *enc, int _C) unsigned quant_coarse_energy(const CELTMode *m, int start, const celt_word16 *eBands, celt_word16 *oldEBands, int budget, int intra, int *prob, celt_word16 *error, ec_enc *enc, int _C, celt_word16 max_decay)
{ {
int i, c; int i, c;
unsigned bits_used = 0; unsigned bits_used = 0;
@ -121,6 +121,12 @@ unsigned quant_coarse_energy(const CELTMode *m, int start, celt_word16 *eBands,
/* Rounding to nearest integer here is really important! */ /* Rounding to nearest integer here is really important! */
qi = (int)floor(.5f+f); qi = (int)floor(.5f+f);
#endif #endif
if (qi < 0 && x < oldEBands[i+c*m->nbEBands]-max_decay)
{
qi += SHR16(oldEBands[i+c*m->nbEBands]-max_decay-x, DB_SHIFT);
if (qi > 0)
qi = 0;
}
/* If we don't have enough bits to encode all the energy, just assume something safe. /* If we don't have enough bits to encode all the energy, just assume something safe.
We allow slightly busting the budget here */ We allow slightly busting the budget here */
bits_used=ec_enc_tell(enc, 0); bits_used=ec_enc_tell(enc, 0);

2
libcelt/quant_bands.h
View file

@ -56,7 +56,7 @@ void compute_fine_allocation(const CELTMode *m, int *bits, int budget);
int intra_decision(celt_word16 *eBands, celt_word16 *oldEBands, int len); int intra_decision(celt_word16 *eBands, celt_word16 *oldEBands, int len);
unsigned quant_coarse_energy(const CELTMode *m, int start, celt_word16 *eBands, celt_word16 *oldEBands, int budget, int intra, int *prob, celt_word16 *error, ec_enc *enc, int _C); unsigned quant_coarse_energy(const CELTMode *m, int start, const celt_word16 *eBands, celt_word16 *oldEBands, int budget, int intra, int *prob, celt_word16 *error, ec_enc *enc, int _C, celt_word16 max_decay);
void quant_fine_energy(const CELTMode *m, int start, celt_ener *eBands, celt_word16 *oldEBands, celt_word16 *error, int *fine_quant, ec_enc *enc, int _C); void quant_fine_energy(const CELTMode *m, int start, celt_ener *eBands, celt_word16 *oldEBands, celt_word16 *error, int *fine_quant, ec_enc *enc, int _C);