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Don't destroy stereo history when switching to mono.

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The first version of the mono decoder with stereo output collapsed
 the historic energy values stored for anti-collapse down to one
 channel (by taking the max).
This means that a subsequent switch back would continue on using
 the the maximum of the two values instead of the original history,
 which would make anti-collapse produce louder noise (and
 potentially more pre-echo than otherwise).

This patch moves the max into the anti_collapse function itself,
 and does not store the values back into the source array, so the
 full stereo history is maintained if subsequent frames switch
 back.
It also fixes an encoder mismatch, which never took the max
 (assuming, apparently, that the output channel count would never
 change).
This commit is contained in:
Timothy B. Terriberry 2011-01-31 13:34:54 -08:00 • committed by Jean-Marc Valin
parent 948d27c9bc
commit 682b6cf1ad
3 changed files with 14 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

6
libcelt/celt.c
View file

@ -1454,7 +1454,7 @@ int celt_encode_with_ec_float(CELTEncoder * restrict st, const celt_sig * pcm, i
#endif
if (anti_collapse_on)
{
anti_collapse(st->mode, X, collapse_masks, LM, C, N,
anti_collapse(st->mode, X, collapse_masks, LM, C, CC, N,
st->start, st->end, oldBandE, oldLogE, oldLogE2, pulses, st->rng);
}
@ -2204,8 +2204,6 @@ int celt_decode_with_ec_float(CELTDecoder * restrict st, const unsigned char *da
for (i=0;i<st->mode->nbEBands;i++)
{
oldBandE[i]=MAX16(oldBandE[i],oldBandE[st->mode->nbEBands+i]);
oldLogE[i]=MAX16(oldLogE[i],oldLogE[st->mode->nbEBands+i]);
oldLogE2[i]=MAX16(oldLogE2[i],oldLogE2[st->mode->nbEBands+i]);
backgroundLogE[i]=MAX16(backgroundLogE[i],backgroundLogE[st->mode->nbEBands+i]);
}
}
@ -2341,7 +2339,7 @@ int celt_decode_with_ec_float(CELTDecoder * restrict st, const unsigned char *da
fine_quant, fine_priority, len*8-ec_dec_tell(dec, 0), dec, C);
if (anti_collapse_on)
anti_collapse(st->mode, X, collapse_masks, LM, C, N,
anti_collapse(st->mode, X, collapse_masks, LM, C, CC, N,
st->start, st->end, oldBandE, oldLogE, oldLogE2, pulses, st->rng);
log2Amp(st->mode, st->start, st->end, bandE, oldBandE, C);