shithub: opus

Info  •  Files  •  Log  •  Branches

In VBR the MDCT modes rate control could dramatically over/undershoot after a frame size change
because the adaptive rate control offset was not being scaled.

--- a/libcelt/celt.c

+++ b/libcelt/celt.c

@@ -1382,8 +1382,9 @@

      /* 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 @@

      /*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);*/