vp9: Allow usage of lookahead for real-time, 1 pass vbr.

Allow usage of lookahead for VBR in real-time mode, for 1 pass vbr.

Current usage is for fast checking of future scene cuts/changes,
and adjusting rate control (gf interval and active_worst/target size).

Added unittests (datarate) for 1 pass vbr mode, with non-zero lag.

Added an experimental option to limit QP based on lookahead.

Overall positive gain in metrics on ytlive set:
avgPNSR/SSIM up on average ~1-3%; several clips up by 5, 7%.

Change-Id: I960d57dfc89de121c4824b9a9bf88d2814e74b56

1 files changed, 29 insertions, 3 deletions

diff --git a/test/datarate_test.cc b/test/datarate_test.cc
index 220cbf3a3..0b188b5d7 100644
--- a/test/datarate_test.cc
+++ b/test/datarate_test.cc
@@ -450,8 +450,8 @@ class DatarateTestVP9Large : public ::libvpx_test::EncoderTest,
   int denoiser_offon_period_;
 };
 
-// Check basic rate targeting for VBR mode.
-TEST_P(DatarateTestVP9Large, BasicRateTargetingVBR) {
+// Check basic rate targeting for VBR mode with 0 lag.
+TEST_P(DatarateTestVP9Large, BasicRateTargetingVBRLagZero) {
   cfg_.rc_min_quantizer = 0;
   cfg_.rc_max_quantizer = 63;
   cfg_.g_error_resilient = 0;
@@ -471,7 +471,33 @@ TEST_P(DatarateTestVP9Large, BasicRateTargetingVBR) {
   }
 }
 
-// Check basic rate targeting for CBR,
+// Check basic rate targeting for VBR mode with non-zero lag.
+TEST_P(DatarateTestVP9Large, BasicRateTargetingVBRLagNonZero) {
+  cfg_.rc_min_quantizer = 0;
+  cfg_.rc_max_quantizer = 63;
+  cfg_.g_error_resilient = 0;
+  cfg_.rc_end_usage = VPX_VBR;
+  // For non-zero lag, rate control will work (be within bounds) for
+  // real-time mode.
+  if (deadline_ == VPX_DL_REALTIME)
+    cfg_.g_lag_in_frames = 15;
+  else
+    cfg_.g_lag_in_frames = 0;
+
+  ::libvpx_test::I420VideoSource video("hantro_collage_w352h288.yuv", 352, 288,
+                                       30, 1, 0, 300);
+  for (int i = 400; i <= 800; i += 400) {
+    cfg_.rc_target_bitrate = i;
+    ResetModel();
+    ASSERT_NO_FATAL_FAILURE(RunLoop(&video));
+    ASSERT_GE(effective_datarate_[0], cfg_.rc_target_bitrate * 0.75)
+        << " The datarate for the file is lower than target by too much!";
+    ASSERT_LE(effective_datarate_[0], cfg_.rc_target_bitrate * 1.25)
+        << " The datarate for the file is greater than target by too much!";
+  }
+}
+
+// Check basic rate targeting for CBR mode.
 TEST_P(DatarateTestVP9Large, BasicRateTargeting) {
   cfg_.rc_buf_initial_sz = 500;
   cfg_.rc_buf_optimal_sz = 500;