NetEq background noise generation off by default

This CL turns the background noise generation in NetEq off by default. The noise generation used to kick in during long-duration packet losses, when there was no point in extrapolating the latest audio any longer. However, this sometimes produces annoying noise in situations where silence would have been preferable.

With this change, a long packet-loss concealment will be faded out to zeros instead of a low noise.

Reference files are updated where needed.

BUG=3519
R=tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/20109004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6882 4adac7df-926f-26a2-2b94-8c16560cd09d

resources/audio_coding/neteq4_network_stats.dat.sha1

@@ -1 +1 @@
-391952a2268cb04b636a6b41868774619a8ae34f
+e5e2d0ff26d16339cf0f37a3512bfa2d390a9a9a

resources/audio_coding/neteq4_universal_ref.pcm.sha1

@@ -1 +1 @@
-49d12cf21b37f2da3f52cf2ab76ecb08adbb2a69
+f587883b7c371ee8d87dbf1b0f07525af7d959b8

resources/audio_coding/neteq4_universal_ref_win_32.pcm.sha1

@@ -1 +1 @@
-49d12cf21b37f2da3f52cf2ab76ecb08adbb2a69
+f587883b7c371ee8d87dbf1b0f07525af7d959b8

resources/audio_coding/neteq4_universal_ref_win_64.pcm.sha1

@@ -1 +1 @@
-84972ecea6a0bf85b873f109c88697eab44cedd3
+08266b198e7686b3cd9330813e0d2cd72fc8fdc2

webrtc/modules/audio_coding/main/acm2/audio_coding_module_unittest.cc

@@ -561,30 +561,38 @@ class AcmReceiverBitExactness : public ::testing::Test {
 };
 
 TEST_F(AcmReceiverBitExactness, 8kHzOutput) {
+  // TODO(henrik.lundin) Update the android checksum once the android bots are
+  // running this test again.
   Run(8000,
-      PlatformChecksum("a53573d9a44a53ea852056e9550fbd53",
+      PlatformChecksum("bd6f8d9602cd82444ea2539e674df747",
                        "7924385273062b9f07aa3d4dff30d601",
-                       "c54fd4a532cdb400bca2758d3a941eee"));
+                       "8a8440f5511eb729221b9aac25cda3a0"));
 }
 
 TEST_F(AcmReceiverBitExactness, 16kHzOutput) {
+  // TODO(henrik.lundin) Update the android checksum once the android bots are
+  // running this test again.
   Run(16000,
-      PlatformChecksum("16ed8ee37bad45de2e1ad2b34c7c3910",
+      PlatformChecksum("a39bc6ee0c4eb15f3ad2f43cebcc571d",
                        "d1d3dde41da936f80fa63d718fbc0fc0",
-                       "68a8b57a0672356f846b3cea51e49903"));
+                       "7be583092c5adbcb0f6cd66eca20ea63"));
 }
 
 TEST_F(AcmReceiverBitExactness, 32kHzOutput) {
+  // TODO(henrik.lundin) Update the android checksum once the android bots are
+  // running this test again.
   Run(32000,
-      PlatformChecksum("f0f41f494d5d811f5a1cfce8fd89d9db",
+      PlatformChecksum("80964572aaa2dc92f9e34896dd3802b3",
                        "23b82b2605e3aab3d4d9e67dba341355",
-                       "f2a69bcdedca515e548cd2c5af75d046"));
+                       "3a84188abe9fca25fedd6034760f3e22"));
 }
 
 TEST_F(AcmReceiverBitExactness, 48kHzOutput) {
+  // TODO(henrik.lundin) Update the android checksum once the android bots are
+  // running this test again.
   Run(48000,
-      PlatformChecksum("77730099d995180ab6cb60379d4a9715",
+      PlatformChecksum("8aacde91f390e0d5a9c2ed571a25fd37",
                        "580c2d0b273ffa8fa0796d784908cbdb",
-                       "5c1bdee51750e13fbb9413bc9280c0dd"));
+                       "89b4b19bdb4de40f1d88302ef8cb9f9b"));
 }
 }  // namespace webrtc

webrtc/modules/audio_coding/neteq/expand.cc

@@ -861,8 +861,8 @@ void Expand::GenerateBackgroundNoise(int16_t* random_vector,
                               mute_slope,
                               noise_samples);
     } else if (bgn_mute_factor < 16384) {
-      // If mode is kBgnOff, or if kBgnFade has started fading,
-      // Use regular |mute_slope|.
+      // If mode is kBgnOn, or if kBgnFade has started fading,
+      // use regular |mute_slope|.
       if (!stop_muting_ && bgn_mode != NetEq::kBgnOff &&
           !(bgn_mode == NetEq::kBgnFade && too_many_expands)) {
         DspHelper::UnmuteSignal(noise_samples,

webrtc/modules/audio_coding/neteq/interface/neteq.h

@@ -74,7 +74,7 @@ class NetEq {
           max_packets_in_buffer(50),
           // |max_delay_ms| has the same effect as calling SetMaximumDelay().
           max_delay_ms(2000),
-          background_noise_mode(kBgnOn) {}
+          background_noise_mode(kBgnOff) {}
 
     int sample_rate_hz;  // Initial vale. Will change with input data.
     bool enable_audio_classifier;