shithub: libvpx

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vp9: Reset buffer level on large bitrate changes.

For a large change in the target avg_frame_bandwidth,
via the update in change_config()), reset the buffer_level
to optimal_level.

This fix prevents possible frame drops, where for example,
encoder suddenly goes from lower to higher bitrate.

Change-Id: I2f844c41d04c01240e85f574e59d2b9075c7eb6d

--- a/vp9/encoder/vp9_encoder.c

+++ b/vp9/encoder/vp9_encoder.c

@@ -1868,6 +1868,7 @@

   // Check for resetting the rc flags (rc_1_frame, rc_2_frame) if the

   // configuration change has a large change in avg_frame_bandwidth.

   // For SVC check for resetting based on spatial layer average bandwidth.

+  // Also reset buffer level to optimal level.

   if (cm->current_video_frame > 0) {

     if (cpi->use_svc) {

       vp9_svc_check_reset_layer_rc_flag(cpi);

@@ -1876,6 +1877,8 @@

           rc->avg_frame_bandwidth < (rc->last_avg_frame_bandwidth >> 1)) {

         rc->rc_1_frame = 0;

         rc->rc_2_frame = 0;

+        rc->bits_off_target = rc->optimal_buffer_level;

+        rc->buffer_level = rc->optimal_buffer_level;

       }

     }

   }

--- a/vp9/encoder/vp9_svc_layercontext.c

+++ b/vp9/encoder/vp9_svc_layercontext.c

@@ -881,6 +881,8 @@

         RATE_CONTROL *lrc = &lc->rc;

         lrc->rc_1_frame = 0;

         lrc->rc_2_frame = 0;

+        lrc->bits_off_target = lrc->optimal_buffer_level;

+        lrc->buffer_level = lrc->optimal_buffer_level;

       }

     }

   }