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Fix crashes with VBR for short duration frames and very low bitrates. This may, however, cause the encoder to violate the rate target at insanely low rates.

Browse source 
This also generally improves VBR behavior by more carefully accounting
for rounding.
This commit is contained in:
Gregory Maxwell 2010-10-28 15:00:37 -04:00 • committed by Jean-Marc Valin
parent a9411472cd
commit fac6c98ce1
1 changed files with 17 additions and 21 deletions
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38
libcelt/celt.c
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@ -132,7 +132,7 @@ CELTEncoder *celt_encoder_init(CELTEncoder *st, const CELTMode *mode, int channe
st->end = st->mode->effEBands;
st->vbr_rate_norm = 0;
st->vbr_offset = -140<<BITRES;
st->vbr_offset = -(64<<BITRES);
st->force_intra = 0;
st->delayedIntra = 1;
st->tonal_average = 256;
@ -800,18 +800,9 @@ int celt_encode_with_ec_float(CELTEncoder * restrict st, const celt_sig * pcm, c
celt_int32 target;
celt_int32 vbr_bound, max_allowed;
vbr_rate = M*st->vbr_rate_norm;
target = vbr_rate = M*st->vbr_rate_norm;
/* Computes the max bit-rate allowed in VBR more to avoid busting the budget */
vbr_bound = vbr_rate;
max_allowed = (vbr_rate + vbr_bound - st->vbr_reservoir)>>(BITRES+3);
if (max_allowed < 4)
max_allowed = 4;
if (max_allowed < nbAvailableBytes)
nbAvailableBytes = max_allowed;
target=vbr_rate;
/* Shortblocks get a large boost in bitrate, but since they
/* Shortblocks get a large boost in bitrate, but since they
are uncommon long blocks are not greatly affected */
if (shortBlocks || tf_sum < -2*(st->end-st->start))
target*=2;
@ -824,15 +815,21 @@ int celt_encode_with_ec_float(CELTEncoder * restrict st, const celt_sig * pcm, c
so far is added*/
target=target+st->vbr_offset+ec_enc_tell(enc, BITRES);
/* In VBR mode the frame size must not be reduced so much that it would result in the coarse energy busting its budget */
target=IMIN(nbAvailableBytes<<(BITRES+3),target);
/* Computes the max bit-rate allowed in VBR more to avoid violating the target rate and buffering */
vbr_bound = vbr_rate;
max_allowed = IMIN(vbr_rate+vbr_bound-st->vbr_reservoir>>(BITRES+3),nbAvailableBytes);
/* In VBR mode the frame size must not be reduced so much that it would result in the encoder running out of bits */
nbAvailableBytes = target+(1<<(BITRES+2))>>(BITRES+3);
nbAvailableBytes=IMAX(16,IMIN(max_allowed,nbAvailableBytes));
target=nbAvailableBytes<<(BITRES+3);
if (st->vbr_count < 970)
{
st->vbr_count++;
alpha = celt_rcp(SHL32(EXTEND32(st->vbr_count+20),16));
} else
alpha = QCONST16(.001f,15);
/* By how much did we "miss" the target on that frame */
delta = (celt_int32)target - vbr_rate;
/* How many bits have we used in excess of what we're allowed */
@ -848,14 +845,12 @@ int celt_encode_with_ec_float(CELTEncoder * restrict st, const celt_sig * pcm, c
if (st->vbr_reservoir < 0)
{
/* We're under the min value -- increase rate */
int adjust = 1-(st->vbr_reservoir-1)/(8<<BITRES);
st->vbr_reservoir += adjust*(8<<BITRES);
target += adjust;
int adjust = (-st->vbr_reservoir)/(8<<BITRES);
nbAvailableBytes += adjust;
st->vbr_reservoir = 0;
/*printf ("+%d\n", adjust);*/
}
if (nbAvailableBytes > target>>(BITRES+3))
nbAvailableBytes = target>>(BITRES+3);
nbCompressedBytes = nbAvailableBytes + nbFilledBytes;
nbCompressedBytes = IMIN(nbCompressedBytes,nbAvailableBytes+nbFilledBytes);
/* This moves the raw bits to take into account the new compressed size */
ec_byte_shrink(&buf, nbCompressedBytes);
@ -1110,6 +1105,7 @@ int celt_encoder_ctl(CELTEncoder * restrict st, int request, ...)
CELT_MEMSET((char*)&st->ENCODER_RESET_START, 0,
celt_encoder_get_size(st->mode, st->channels)-
((char*)&st->ENCODER_RESET_START - (char*)st));
st->vbr_offset = -(64<<BITRES);
st->delayedIntra = 1;
st->fold_decision = 1;
st->tonal_average = QCONST16(1.f,8);