From a975c75748367ff70493c701faad7a756468d836 Mon Sep 17 00:00:00 2001
From: tofunmi <tofunmi@google.com>
Date: Fri, 8 Mar 2024 09:58:47 -0800
Subject: [PATCH] SpeedChangingAudioProcessor: fix outputTime calculation

minor fix for arithmetic error in calculated added in https://github.com/androidx/media/commit/f4c60c52b9a97ad007a2387e4d91be0142a9b75b (speed is outputTime (change in y) divided by inputTime (change in x), this calculation is inverted in code).

Changed test to cover the case.

PiperOrigin-RevId: 613966027
---
 .../audio/SpeedChangingAudioProcessor.java    | 26 +++++++++++++------
 .../SpeedChangingAudioProcessorTest.java      |  5 ++--
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/libraries/common/src/main/java/androidx/media3/common/audio/SpeedChangingAudioProcessor.java b/libraries/common/src/main/java/androidx/media3/common/audio/SpeedChangingAudioProcessor.java
index 26852f38b2..5e62497dee 100644
--- a/libraries/common/src/main/java/androidx/media3/common/audio/SpeedChangingAudioProcessor.java
+++ b/libraries/common/src/main/java/androidx/media3/common/audio/SpeedChangingAudioProcessor.java
@@ -17,6 +17,7 @@
 package androidx.media3.common.audio;
 
 import static java.lang.Math.min;
+import static java.lang.Math.round;
 
 import androidx.media3.common.C;
 import androidx.media3.common.util.LongArray;
@@ -210,17 +211,26 @@ public final class SpeedChangingAudioProcessor extends BaseAudioProcessor {
       floorIndex--;
     }
     long lastSegmentInputDuration = inputTimeUs - inputSegmentStartTimesUs.get(floorIndex);
-    long lastSegmentOutputDuration =
-        floorIndex == inputSegmentStartTimesUs.size() - 1
-            ? getPlayoutDurationAtCurrentSpeed(lastSegmentInputDuration)
-            : lastSegmentInputDuration
-                * (inputSegmentStartTimesUs.get(floorIndex + 1)
-                    - inputSegmentStartTimesUs.get(floorIndex))
-                / (outputSegmentStartTimesUs.get(floorIndex + 1)
-                    - outputSegmentStartTimesUs.get(floorIndex));
+    long lastSegmentOutputDuration;
+    if (floorIndex == inputSegmentStartTimesUs.size() - 1) {
+      lastSegmentOutputDuration = getPlayoutDurationAtCurrentSpeed(lastSegmentInputDuration);
+    } else {
+      lastSegmentOutputDuration =
+          round(
+              lastSegmentInputDuration
+                  * divide(
+                      outputSegmentStartTimesUs.get(floorIndex + 1)
+                          - outputSegmentStartTimesUs.get(floorIndex),
+                      inputSegmentStartTimesUs.get(floorIndex + 1)
+                          - inputSegmentStartTimesUs.get(floorIndex)));
+    }
     return outputSegmentStartTimesUs.get(floorIndex) + lastSegmentOutputDuration;
   }
 
+  private static double divide(long dividend, long divisor) {
+    return ((double) dividend) / divisor;
+  }
+
   private void processPendingCallbacks() {
     synchronized (pendingCallbacksLock) {
       while (!pendingCallbacks.isEmpty()
diff --git a/libraries/common/src/test/java/androidx/media3/common/audio/SpeedChangingAudioProcessorTest.java b/libraries/common/src/test/java/androidx/media3/common/audio/SpeedChangingAudioProcessorTest.java
index 74caffbe42..84ee57bae4 100644
--- a/libraries/common/src/test/java/androidx/media3/common/audio/SpeedChangingAudioProcessorTest.java
+++ b/libraries/common/src/test/java/androidx/media3/common/audio/SpeedChangingAudioProcessorTest.java
@@ -357,7 +357,7 @@ public class SpeedChangingAudioProcessorTest {
     // The speed change is at 113Us (5*MICROS_PER_SECOND/sampleRate).
     SpeedProvider speedProvider =
         TestSpeedProvider.createWithFrameCounts(
-            AUDIO_FORMAT, /* frameCounts= */ new int[] {5, 5}, /* speeds= */ new float[] {1, 2});
+            AUDIO_FORMAT, /* frameCounts= */ new int[] {5, 5}, /* speeds= */ new float[] {2, 1});
     SpeedChangingAudioProcessor speedChangingAudioProcessor =
         getConfiguredSpeedChangingAudioProcessor(speedProvider);
     ByteBuffer inputBuffer = getInputBuffer(/* frameCount= */ 5);
@@ -374,7 +374,8 @@ public class SpeedChangingAudioProcessorTest {
     speedChangingAudioProcessor.getSpeedAdjustedTimeAsync(
         /* inputTimeUs= */ 150L, outputTimesUs::add);
 
-    assertThat(outputTimesUs).containsExactly(50L, 100L, 131L);
+    // 150 is after the speed change so floor(113 / 2 + (150 - 113)*1) -> 93
+    assertThat(outputTimesUs).containsExactly(25L, 50L, 93L);
   }
 
   private static SpeedChangingAudioProcessor getConfiguredSpeedChangingAudioProcessor(