Index: encoder/ratecontrol.c
===================================================================
--- encoder/ratecontrol.c	(revision 736)
+++ encoder/ratecontrol.c	(working copy)
@@ -762,6 +899,15 @@
     return bits;
 }
 
+double row_bits_so_far( x264_t *h, int y )
+{
+    int i;
+    double bits = 0;
+    for( i = 0; i <= y; i++ )
+        bits += h->fdec->i_row_bits[i];
+    return bits;
+}
+
 void x264_ratecontrol_mb( x264_t *h, int bits )
 {
     x264_ratecontrol_t *rc = h->rc;
@@ -783,10 +929,10 @@
         /* B-frames shouldn't use lower QP than their reference frames */
         if( y < h->sps->i_mb_height-1 )
         {
-            rc->qpm = X264_MAX( rc->qp,
-                      X264_MIN( h->fref0[0]->i_row_qp[y+1],
-                                h->fref1[0]->i_row_qp[y+1] ));
+            int avg_qp = (h->fref0[0]->i_row_qp[y+1]+h->fref1[0]->i_row_qp[y+1])*0.5+rc->pb_offset * ((h->fenc->i_type == X264_TYPE_BREF) ? 0.5 : 1);
+            rc->qpm = X264_MAX( rc->qp, avg_qp);
         }
+        //printf("Frame: %d QP: %d PrevQP: %d NextQP: %d NewQP: %d\n",h->i_frame,rc->qp,h->fref0[0]->i_row_qp[y+1],h->fref1[0]->i_row_qp[y+1],rc->qpm);
     }
     else
     {
@@ -800,13 +946,47 @@
             int b1 = b0;
             int i_qp_max = X264_MIN( prev_row_qp + h->param.rc.i_qp_step, h->param.rc.i_qp_max );
             int i_qp_min = X264_MAX( prev_row_qp - h->param.rc.i_qp_step, h->param.rc.i_qp_min );
-            float buffer_left_planned = rc->buffer_fill - rc->frame_size_planned;
+            float actual_size_planned = rc->frame_size_planned;
+           /* Don't modify the row QPs until a suffient amount of the bits of the frame have been processed, in case a flat */
+           /* area at the top of the frame was measured inaccurately. */
+            if(row_bits_so_far(h,y) < 0.15 * actual_size_planned)
+            {
+                return;
+            }
+            /* If this frame is a P-frame, make sure it isn't too large. */
+            if(h->sh.i_type != SLICE_TYPE_I)
+            {
+                /*if(actual_size_planned > 2 * rc->buffer_rate)
+                {
+                    float min_size = 2 * rc->buffer_rate;
+                    actual_size_planned *= powf(min_size/actual_size_planned,0.8);
+                }*/
+            }
+            /* If this frame is an I-frame and isn't too large, don't run the rest of row MBRC */
+            else if(b1 < rc->buffer_fill * 0.6)
+            {
+                /* If the current row is higher QP than the frame QP, try lowering the QP */
+                if(h->fdec->i_row_qp[0] < rc->qpm)
+                {
+                    while(b1 < rc->buffer_fill * 0.6 && rc->qpm > h->fdec->i_row_qp[0])
+                    {
+                        rc->qpm--;
+                        b1 = predict_row_size_sum( h, y, rc->qpm );
+                    }
+                    return;
+                }
+                else
+                    return;
+            }
+            /* Don't let I-frames take up more than 60% of the remaining buffer. */
+            else actual_size_planned = rc->buffer_fill * 0.6;
+            float buffer_left_planned = rc->buffer_fill - actual_size_planned;
 
             if( !rc->b_vbv_min_rate )
                 i_qp_min = X264_MAX( i_qp_min, h->sh.i_qp );
 
             while( rc->qpm < i_qp_max
-                   && (b1 > rc->frame_size_planned * 1.15
+                   && (b1 > actual_size_planned * 1.15
                     || (rc->buffer_fill - b1 < buffer_left_planned * 0.5)))
             {
                 rc->qpm ++;
@@ -814,8 +994,8 @@
             }
 
             while( rc->qpm > i_qp_min
-                   && buffer_left_planned > rc->buffer_size * 0.4
-                   && ((b1 < rc->frame_size_planned * 0.8 && rc->qpm <= prev_row_qp)
+                   && ((buffer_left_planned > rc->buffer_size * 0.4) || rc->qpm > h->fdec->i_row_qp[0])
+                   && ((b1 < actual_size_planned * 0.8 && rc->qpm <= prev_row_qp)
                      || b1 < (rc->buffer_fill - rc->buffer_size + rc->buffer_rate) * 1.1) )
             {
                 rc->qpm --;
@@ -1191,8 +1373,8 @@
         ( pict_type == SLICE_TYPE_P ||
           ( pict_type == SLICE_TYPE_I && rcc->last_non_b_pict_type == SLICE_TYPE_I ) ) )
     {
-        if( rcc->buffer_fill/rcc->buffer_size < 0.5 )
-            q /= x264_clip3f( 2.0*rcc->buffer_fill/rcc->buffer_size, 0.5, 1.0 );
+        float filled = 1.0 - rcc->buffer_fill/rcc->buffer_size;
+        q *= (1/0.544331054) / pow(2 - filled,1.5);
     }
 
     if( rcc->b_vbv && rcc->last_satd > 0 )