From: Fiona Glaser <fiona@x264.com>
Date: Wed, 28 Jan 2009 07:27:56 +0000 (-0800)
Subject: Hack around a potential failure point in VBV
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d4ca70f8398bdba2391fbcea4886ee0577494b08;p=libx264

Hack around a potential failure point in VBV
pred_b_from_p can become absurdly large in static scenes, leading to rare collapses of quality with VBV+B-frames+threads.
This isn't a final fix, but should resolve the problem in most cases in the meantime.
---

diff --git a/encoder/ratecontrol.c b/encoder/ratecontrol.c
index 96b67de6..c0a4bd76 100644
--- a/encoder/ratecontrol.c
+++ b/encoder/ratecontrol.c
@@ -1147,6 +1147,10 @@ void x264_ratecontrol_end( x264_t *h, int bits )
             {
                 update_predictor( rc->pred_b_from_p, qp2qscale(rc->qpa_rc),
                                   h->fref1[h->i_ref1-1]->i_satd, rc->bframe_bits / rc->bframes );
+                /* In some cases, such as completely blank scenes, pred_b_from_p can go nuts */
+                /* Hackily cap the predictor coeff in case this happens. */
+                /* FIXME FIXME FIXME */
+                rc->pred_b_from_p->coeff = X264_MIN( rc->pred_b_from_p->coeff, 10. );
                 rc->bframe_bits = 0;
             }
         }