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In VBR the MDCT modes rate control could dramatically over/undershoot after a frame size change

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because the adaptive rate control offset was not being scaled.
This commit is contained in:
Gregory Maxwell 2011-08-23 02:00:55 -04:00 • committed by Jean-Marc Valin
parent 9f555bc4e7
commit de0b977547
1 changed files with 3 additions and 2 deletions
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5
libcelt/celt.c
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@ -1382,8 +1382,9 @@ int celt_encode_with_ec(CELTEncoder * restrict st, const opus_val16 * pcm, int f
/* The target rate in 8th bits per frame */
opus_int32 target;
opus_int32 min_allowed;
int lm_diff = st->mode->maxLM - LM;
target = vbr_rate + st->vbr_offset - ((40*C+20)<<BITRES);
target = vbr_rate + (st->vbr_offset>>lm_diff) - ((40*C+20)<<BITRES);
/* Shortblocks get a large boost in bitrate, but since they
are uncommon long blocks are not greatly affected */
@ -1437,7 +1438,7 @@ int celt_encode_with_ec(CELTEncoder * restrict st, const opus_val16 * pcm, int f
/*printf ("%d\n", st->vbr_reservoir);*/
/* Compute the offset we need to apply in order to reach the target */
st->vbr_drift += (opus_int32)MULT16_32_Q15(alpha,delta-st->vbr_offset-st->vbr_drift);
st->vbr_drift += (opus_int32)MULT16_32_Q15(alpha,(delta<<lm_diff)-st->vbr_offset-st->vbr_drift);
st->vbr_offset = -st->vbr_drift;
/*printf ("%d\n", st->vbr_drift);*/