Spatializer: Tuning for least squares prediction

Made the prediction verifier more extensible for testing.

Allow audio.spatializer.prediction_duration_ms == 0
for testing.

Test: adb shell dumpsys media.audio_policy
Bug: 274847421
Change-Id: I1ffd9510a29bcca6c043c7e282f7d1fa1e3ed4ce
diff --git a/media/libheadtracking/PosePredictor.cpp b/media/libheadtracking/PosePredictor.cpp
index f67a966..5209d54 100644
--- a/media/libheadtracking/PosePredictor.cpp
+++ b/media/libheadtracking/PosePredictor.cpp
@@ -91,20 +91,23 @@
 
 // Formatting
 static inline std::vector<size_t> createDelimiterIdx(size_t predictors, size_t lookaheads) {
-    if (predictors == 0) return {};
-    --predictors;
-    std::vector<size_t> delimiterIdx(predictors);
-    for (size_t i = 0; i < predictors; ++i) {
-        delimiterIdx[i] = (i + 1) * lookaheads;
+    if (lookaheads == 0) return {};
+    --lookaheads;
+    std::vector<size_t> delimiterIdx(lookaheads);
+    for (size_t i = 0; i < lookaheads; ++i) {
+        delimiterIdx[i] = (i + 1) * predictors;
     }
     return delimiterIdx;
 }
 
 PosePredictor::PosePredictor()
-    : mPredictors{  // must match switch in getCurrentPredictor()
+    : mPredictors{
+            // First predictors must match switch in getCurrentPredictor()
             std::make_shared<LastPredictor>(),
             std::make_shared<TwistPredictor>(),
             std::make_shared<LeastSquaresPredictor>(),
+            // After this, can place additional predictors here for comparison such as
+            // std::make_shared<LeastSquaresPredictor>(0.25),
         }
     , mLookaheadMs(kLookAheadMs.begin(), kLookAheadMs.end())
     , mVerifiers(std::size(mLookaheadMs) * std::size(mPredictors))
@@ -195,7 +198,12 @@
     if constexpr (kEnableVerification) {
         // dump verification
         ss.append(prefixSpace)
-            .append(" Prediction abs error (L1) degrees [ type (last twist least-squares) x ( ");
+            .append(" Prediction abs error (L1) degrees [ type (");
+        for (size_t i = 0; i < mPredictors.size(); ++i) {
+            if (i > 0) ss.append(" , ");
+            ss.append(mPredictors[i]->name());
+        }
+        ss.append(" ) x ( ");
         for (size_t i = 0; i < mLookaheadMs.size(); ++i) {
             if (i > 0) ss.append(" : ");
             ss.append(std::to_string(mLookaheadMs[i]));
diff --git a/media/libheadtracking/PosePredictor.h b/media/libheadtracking/PosePredictor.h
index 06983cc..53211e3 100644
--- a/media/libheadtracking/PosePredictor.h
+++ b/media/libheadtracking/PosePredictor.h
@@ -32,6 +32,7 @@
     virtual void add(int64_t atNs, const Pose3f& pose, const Twist3f& twist) = 0;
     virtual Pose3f predict(int64_t atNs) const = 0;
     virtual void reset() = 0;
+    virtual std::string name() const = 0;
     virtual std::string toString(size_t index) const = 0;
 };
 
@@ -57,6 +58,10 @@
         mLastPose = {};
     }
 
+    std::string name() const override {
+        return "LAST";
+    }
+
     std::string toString(size_t index) const override {
         std::string s(index, ' ');
         s.append("LastPredictor using last pose: ")
@@ -92,6 +97,10 @@
         mLastTwist = {};
     }
 
+    std::string name() const override {
+        return "TWIST";
+    }
+
     std::string toString(size_t index) const override {
         std::string s(index, ' ');
         s.append("TwistPredictor using last pose: ")
@@ -130,13 +139,16 @@
     void add(int64_t atNs, const Pose3f& pose, const Twist3f& twist) override;
     Pose3f predict(int64_t atNs) const override;
     void reset() override;
+    std::string name() const override {
+        return "LEAST_SQUARES(" + std::to_string(mAlpha) + ")";
+    }
     std::string toString(size_t index) const override;
 
 private:
     const double mAlpha;
     int64_t mLastAtNs{};
     Pose3f mLastPose;
-    static constexpr double kDefaultAlphaEstimator = 0.5;
+    static constexpr double kDefaultAlphaEstimator = 0.2;
     static constexpr size_t kMinimumSamplesForPrediction = 4;
     audio_utils::LinearLeastSquaresFit<double> mRw;
     audio_utils::LinearLeastSquaresFit<double> mRx;
diff --git a/services/audiopolicy/service/SpatializerPoseController.cpp b/services/audiopolicy/service/SpatializerPoseController.cpp
index d325509..874bde4 100644
--- a/services/audiopolicy/service/SpatializerPoseController.cpp
+++ b/services/audiopolicy/service/SpatializerPoseController.cpp
@@ -108,8 +108,8 @@
               .freshnessTimeout = Ticks(kFreshnessTimeout).count(),
               .predictionDuration = []() -> float {
                   const int duration_ms =
-                          property_get_int32("audio.spatializer.prediction_duration_ms", 0);
-                  if (duration_ms > 0) {
+                          property_get_int32("audio.spatializer.prediction_duration_ms", -1);
+                  if (duration_ms >= 0) {
                       return duration_ms * 1'000'000LL;
                   } else {
                       return Ticks(kPredictionDuration).count();