Optimize the repeated calls to AudioEffect.queryEffects() on Android

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java

Index: webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java
diff --git a/webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java b/webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java
index e5408fd81b5bc36459f3f9a24eb1365b16970819..255e92d9ec98389a6bef34ee677d818f3020b5d9 100644
--- a/webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java
+++ b/webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java
@@ -42,6 +42,11 @@ class WebRtcAudioEffects {
   private static final UUID AOSP_NOISE_SUPPRESSOR =
       UUID.fromString("c06c8400-8e06-11e0-9cb6-0002a5d5c51b");
 
+  // Contains the available effect descriptors returned from the
+  // AudioEffect.getEffects() call. This result is cached to avoid doing the
+  // slow OS call multiple times.
+  private static Descriptor[] cachedEffects = null;
+
   // Contains the audio effect objects. Created in enable() and destroyed
   // in release().
   private AcousticEchoCanceler aec = null;
@@ -60,22 +65,31 @@ class WebRtcAudioEffects {
   // Checks if the device implements Acoustic Echo Cancellation (AEC).
   // Returns true if the device implements AEC, false otherwise.
   public static boolean isAcousticEchoCancelerSupported() {
+    // Note: we're using isAcousticEchoCancelerEffectAvailable() instead of
+    // AcousticEchoCanceler.isAvailable() to avoid the expensive getEffects()
+    // OS API call.
     return WebRtcAudioUtils.runningOnJellyBeanOrHigher()
-        && AcousticEchoCanceler.isAvailable();
+        && isAcousticEchoCancelerEffectAvailable();
   }
 
   // Checks if the device implements Automatic Gain Control (AGC).
   // Returns true if the device implements AGC, false otherwise.
   public static boolean isAutomaticGainControlSupported() {
+    // Note: we're using isAutomaticGainControlEffectAvailable() instead of
+    // AutomaticGainControl.isAvailable() to avoid the expensive getEffects()
+    // OS API call.
     return WebRtcAudioUtils.runningOnJellyBeanOrHigher()
-        && AutomaticGainControl.isAvailable();
+        && isAutomaticGainControlEffectAvailable();
   }
 
   // Checks if the device implements Noise Suppression (NS).
   // Returns true if the device implements NS, false otherwise.
   public static boolean isNoiseSuppressorSupported() {
+    // Note: we're using isNoiseSuppressorEffectAvailable() instead of
+    // NoiseSuppressor.isAvailable() to avoid the expensive getEffects()
+    // OS API call.
     return WebRtcAudioUtils.runningOnJellyBeanOrHigher()
-        && NoiseSuppressor.isAvailable();
+        && isNoiseSuppressorEffectAvailable();
   }
 
   // Returns true if the device is blacklisted for HW AEC usage.
@@ -115,7 +129,7 @@ class WebRtcAudioEffects {
   // AudioEffect.queryEffects() can throw IllegalStateException.
   @TargetApi(18)
   private static boolean isAcousticEchoCancelerExcludedByUUID() {
-    for (Descriptor d : AudioEffect.queryEffects()) {
+    for (Descriptor d : getAvailableEffects()) {
       if (d.type.equals(AudioEffect.EFFECT_TYPE_AEC) &&
           d.uuid.equals(AOSP_ACOUSTIC_ECHO_CANCELER)) {
         return true;
@@ -128,7 +142,7 @@ class WebRtcAudioEffects {
   // AudioEffect.queryEffects() can throw IllegalStateException.
   @TargetApi(18)
   private static boolean isAutomaticGainControlExcludedByUUID() {
-    for (Descriptor d : AudioEffect.queryEffects()) {
+    for (Descriptor d : getAvailableEffects()) {
       if (d.type.equals(AudioEffect.EFFECT_TYPE_AGC) &&
           d.uuid.equals(AOSP_AUTOMATIC_GAIN_CONTROL)) {
         return true;
@@ -141,7 +155,7 @@ class WebRtcAudioEffects {
   // AudioEffect.queryEffects() can throw IllegalStateException.
   @TargetApi(18)
   private static boolean isNoiseSuppressorExcludedByUUID() {
-    for (Descriptor d : AudioEffect.queryEffects()) {
+    for (Descriptor d : getAvailableEffects()) {
       if (d.type.equals(AudioEffect.EFFECT_TYPE_NS) &&
           d.uuid.equals(AOSP_NOISE_SUPPRESSOR)) {
         return true;
@@ -150,6 +164,24 @@ class WebRtcAudioEffects {
     return false;
   }
 
+  // Returns true if the device supports Acoustic Echo Cancellation (AEC).
+  @TargetApi(18)
+  private static boolean isAcousticEchoCancelerEffectAvailable() {
+    return isEffectTypeAvailable(AudioEffect.EFFECT_TYPE_AEC);
+  }
+
+  // Returns true if the device supports Automatic Gain Control (AGC).
+  @TargetApi(18)
+  private static boolean isAutomaticGainControlEffectAvailable() {
+    return isEffectTypeAvailable(AudioEffect.EFFECT_TYPE_AGC);
+  }
+
+  // Returns true if the device supports Noise Suppression (NS).
+  @TargetApi(18)
+  private static boolean isNoiseSuppressorEffectAvailable() {
+    return isEffectTypeAvailable(AudioEffect.EFFECT_TYPE_NS);
+  }
+
   // Returns true if all conditions for supporting the HW AEC are fulfilled.
   // It will not be possible to enable the HW AEC if this method returns false.
   public static boolean canUseAcousticEchoCanceler() {
@@ -378,4 +410,34 @@ class WebRtcAudioEffects {
       throw new AssertionError("Expected condition to be true");
     }
   }
+
+  // Returns the cached copy of the audio effects array, if available, or
+  // queries the operating system for the list of effects.
+  private static Descriptor[] getAvailableEffects() {
+    if (cachedEffects != null) {
+      return cachedEffects;
+    }
+    // The caching is best effort only - if this method is called from several
+    // threads in parallel, they may end up doing the underlying OS call
+    // multiple times. It's normally only called on one thread so there's no
+    // real need to optimize for the multiple threads case.
+    cachedEffects = AudioEffect.queryEffects();
+    return cachedEffects;
+  }
+
+  // Returns true if an effect of the specified type is available. Functionally
+  // equivalent to (NoiseSuppressor|AutomaticGainControl|...).isAvailable(), but
+  // faster as it avoids the expensive OS call to enumerate effects.
+  private static boolean isEffectTypeAvailable(UUID effectType) {
+    Descriptor[] effects = getAvailableEffects();
+    if (effects == null) {
+      return false;
+    }
+    for (Descriptor d : effects) {
+      if (d.type.equals(effectType)) {
+        return true;
+      }
+    }
+    return false;
+  }
 }