--- a/dom/media/encoder/VP8TrackEncoder.cpp
+++ b/dom/media/encoder/VP8TrackEncoder.cpp
@@ -124,17 +124,17 @@ VP8TrackEncoder::Init(int32_t aWidth, in
   } else if (mFrameWidth * mFrameHeight > 640 * 480 && number_of_cores >= 3) {
     config.g_threads = 2; // 2 threads for qHD/HD.
   } else {
     config.g_threads = 1; // 1 thread for VGA or less
   }
 
   // rate control settings
   config.rc_dropframe_thresh = 0;
-  config.rc_end_usage = VPX_CBR;
+  config.rc_end_usage = VPX_VBR;
   config.g_pass = VPX_RC_ONE_PASS;
   // ffmpeg doesn't currently support streams that use resize.
   // Therefore, for safety, we should turn it off until it does.
   config.rc_resize_allowed = 0;
   config.rc_undershoot_pct = 100;
   config.rc_overshoot_pct = 15;
   config.rc_buf_initial_sz = 500;
   config.rc_buf_optimal_sz = 600;