Add method to obtain media duration from playout duration

This is the inverse operation of the already existing method.

PiperOrigin-RevId: 633207017

libraries/common/src/main/java/androidx/media3/common/audio/SpeedChangingAudioProcessor.java

@@ -226,6 +226,41 @@ public final class SpeedChangingAudioProcessor extends BaseAudioProcessor {
     }
   }
 
+  /**
+   * Returns the input media duration for the given playout duration.
+   *
+   * <p>Both durations are counted from the last {@link #reset()} or {@link #flush()} of the audio
+   * processor.
+   *
+   * <p>The {@code playoutDurationUs} must be less than last processed buffer output time.
+   *
+   * @param playoutDurationUs The playout duration in microseconds.
+   * @return The corresponding input duration in microseconds.
+   */
+  public long getMediaDurationUs(long playoutDurationUs) {
+    int floorIndex = outputSegmentStartTimesUs.size() - 1;
+    while (floorIndex > 0 && outputSegmentStartTimesUs.get(floorIndex) > playoutDurationUs) {
+      floorIndex--;
+    }
+    long lastSegmentOutputDurationUs =
+        playoutDurationUs - outputSegmentStartTimesUs.get(floorIndex);
+    long lastSegmentInputDurationUs;
+    if (floorIndex == outputSegmentStartTimesUs.size() - 1) {
+      lastSegmentInputDurationUs = getMediaDurationUsAtCurrentSpeed(lastSegmentOutputDurationUs);
+
+    } else {
+      lastSegmentInputDurationUs =
+          round(
+              lastSegmentOutputDurationUs
+                  * divide(
+                      inputSegmentStartTimesUs.get(floorIndex + 1)
+                          - inputSegmentStartTimesUs.get(floorIndex),
+                      outputSegmentStartTimesUs.get(floorIndex + 1)
+                          - outputSegmentStartTimesUs.get(floorIndex)));
+    }
+    return inputSegmentStartTimesUs.get(floorIndex) + lastSegmentInputDurationUs;
+  }
+
   /**
    * Assuming enough audio has been processed, calculates the time at which the {@code inputTimeUs}
    * is outputted at after the speed changes has been applied.
@@ -293,6 +328,12 @@ public final class SpeedChangingAudioProcessor extends BaseAudioProcessor {
         : mediaDurationUs;
   }
 
+  private long getMediaDurationUsAtCurrentSpeed(long playoutDurationUs) {
+    return isUsingSonic()
+        ? sonicAudioProcessor.getMediaDuration(playoutDurationUs)
+        : playoutDurationUs;
+  }
+
   private long updateLastProcessedInputTime() {
     if (isUsingSonic()) {
       // TODO - b/320242819: Investigate whether bytesRead can be used here rather than

libraries/common/src/test/java/androidx/media3/common/audio/SpeedChangingAudioProcessorTest.java

@@ -493,6 +493,44 @@ public class SpeedChangingAudioProcessorTest {
     assertThat(outputTimesUs).containsExactly(243L);
   }
 
+  @Test
+  public void getMediaDurationUs_returnsCorrectValues() throws Exception {
+    // The speed changes happen every 10ms (441 samples @ 441.KHz)
+    SpeedProvider speedProvider =
+        TestSpeedProvider.createWithFrameCounts(
+            AUDIO_FORMAT,
+            /* frameCounts= */ new int[] {441, 441, 441, 441},
+            /* speeds= */ new float[] {2, 1, 5, 2});
+    SpeedChangingAudioProcessor speedChangingAudioProcessor =
+        getConfiguredSpeedChangingAudioProcessor(speedProvider);
+    ByteBuffer inputBuffer = getInputBuffer(/* frameCount= */ 441 * 4);
+    while (inputBuffer.position() < inputBuffer.limit()) {
+      speedChangingAudioProcessor.queueInput(inputBuffer);
+    }
+    getAudioProcessorOutput(speedChangingAudioProcessor);
+
+    // input (in ms) (0, 10, 20, 30, 40) ->
+    // output (in ms) (0, 10/2, 10/2 + 10, 10/2 + 10 + 10/5, 10/2 + 10 + 10/5 + 10/2)
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 0))
+        .isEqualTo(0);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 3_000))
+        .isEqualTo(6_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 5_000))
+        .isEqualTo(10_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 10_000))
+        .isEqualTo(15_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 15_000))
+        .isEqualTo(20_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 16_000))
+        .isEqualTo(25_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 17_000))
+        .isEqualTo(30_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 18_000))
+        .isEqualTo(32_000);
+    assertThat(speedChangingAudioProcessor.getMediaDurationUs(/* playoutDurationUs= */ 22_000))
+        .isEqualTo(40_000);
+  }
+
   private static SpeedChangingAudioProcessor getConfiguredSpeedChangingAudioProcessor(
       SpeedProvider speedProvider) throws AudioProcessor.UnhandledAudioFormatException {
     SpeedChangingAudioProcessor speedChangingAudioProcessor =