Fix position jank after pausing and seeking

Issue: #6901
PiperOrigin-RevId: 314418536

RELEASENOTES.md

@@ -186,6 +186,9 @@
 
 ### 2.11.5 (2020-06-03) ###
 
+*   Improve the smoothness of video playback immediately after starting, seeking
+    or resuming a playback
+    ([#6901](https://github.com/google/ExoPlayer/issues/6901)).
 *   Add `SilenceMediaSource.Factory` to support tags.
 *   Enable the configuration of `SilenceSkippingAudioProcessor`
     ([#6705](https://github.com/google/ExoPlayer/issues/6705)).

library/core/src/main/java/com/google/android/exoplayer2/audio/AudioTimestampPoller.java

@@ -38,7 +38,7 @@
  *
  * <p>If {@link #hasTimestamp()} returns {@code true}, call {@link #getTimestampSystemTimeUs()} to
  * get the system time at which the latest timestamp was sampled and {@link
- * #getTimestampPositionFrames()} to get its position in frames. If {@link #isTimestampAdvancing()}
+ * #getTimestampPositionFrames()} to get its position in frames. If {@link #hasAdvancingTimestamp()}
  * returns {@code true}, the caller should assume that the timestamp has been increasing in real
  * time since it was sampled. Otherwise, it may be stationary.
  *
@@ -69,7 +69,7 @@
   private static final int STATE_ERROR = 4;
 
   /** The polling interval for {@link #STATE_INITIALIZING} and {@link #STATE_TIMESTAMP}. */
-  private static final int FAST_POLL_INTERVAL_US = 5_000;
+  private static final int FAST_POLL_INTERVAL_US = 10_000;
   /**
    * The polling interval for {@link #STATE_TIMESTAMP_ADVANCING} and {@link #STATE_NO_TIMESTAMP}.
    */
@@ -111,7 +111,7 @@ public AudioTimestampPoller(AudioTrack audioTrack) {
    * timestamp is available via {@link #getTimestampSystemTimeUs()} and {@link
    * #getTimestampPositionFrames()}, and the caller should call {@link #acceptTimestamp()} if the
    * timestamp was valid, or {@link #rejectTimestamp()} otherwise. The values returned by {@link
-   * #hasTimestamp()} and {@link #isTimestampAdvancing()} may be updated.
+   * #hasTimestamp()} and {@link #hasAdvancingTimestamp()} may be updated.
    *
    * @param systemTimeUs The current system time, in microseconds.
    * @return Whether the timestamp was updated.
@@ -202,12 +202,12 @@ public boolean hasTimestamp() {
   }
 
   /**
-   * Returns whether the timestamp appears to be advancing. If {@code true}, call {@link
+   * Returns whether this instance has an advancing timestamp. If {@code true}, call {@link
    * #getTimestampSystemTimeUs()} and {@link #getTimestampSystemTimeUs()} to access the timestamp. A
    * current position for the track can be extrapolated based on elapsed real time since the system
    * time at which the timestamp was sampled.
    */
-  public boolean isTimestampAdvancing() {
+  public boolean hasAdvancingTimestamp() {
     return state == STATE_TIMESTAMP_ADVANCING;
   }
 

library/core/src/main/java/com/google/android/exoplayer2/audio/AudioTrackPositionTracker.java

@@ -123,6 +123,8 @@ void onSystemTimeUsMismatch(
    * <p>This is a fail safe that should not be required on correctly functioning devices.
    */
   private static final long MAX_LATENCY_US = 5 * C.MICROS_PER_SECOND;
+  /** The duration of time used to smooth over an adjustment between position sampling modes. */
+  private static final long MODE_SWITCH_SMOOTHING_DURATION_US = C.MICROS_PER_SECOND;
 
   private static final long FORCE_RESET_WORKAROUND_TIMEOUT_MS = 200;
 
@@ -160,6 +162,15 @@ void onSystemTimeUsMismatch(
   private long stopPlaybackHeadPosition;
   private long endPlaybackHeadPosition;
 
+  // Results from the previous call to getCurrentPositionUs.
+  private long lastPositionUs;
+  private long lastSystemTimeUs;
+  private boolean lastSampleUsedGetTimestampMode;
+
+  // Results from the last call to getCurrentPositionUs that used a different sample mode.
+  private long previousModePositionUs;
+  private long previousModeSystemTimeUs;
+
   /**
    * Creates a new audio track position tracker.
    *
@@ -218,18 +229,16 @@ public long getCurrentPositionUs(boolean sourceEnded) {
     // If the device supports it, use the playback timestamp from AudioTrack.getTimestamp.
     // Otherwise, derive a smoothed position by sampling the track's frame position.
     long systemTimeUs = System.nanoTime() / 1000;
+    long positionUs;
     AudioTimestampPoller audioTimestampPoller = Assertions.checkNotNull(this.audioTimestampPoller);
-    if (audioTimestampPoller.hasTimestamp()) {
+    boolean useGetTimestampMode = audioTimestampPoller.hasAdvancingTimestamp();
+    if (useGetTimestampMode) {
       // Calculate the speed-adjusted position using the timestamp (which may be in the future).
       long timestampPositionFrames = audioTimestampPoller.getTimestampPositionFrames();
       long timestampPositionUs = framesToDurationUs(timestampPositionFrames);
-      if (!audioTimestampPoller.isTimestampAdvancing()) {
-        return timestampPositionUs;
-      }
       long elapsedSinceTimestampUs = systemTimeUs - audioTimestampPoller.getTimestampSystemTimeUs();
-      return timestampPositionUs + elapsedSinceTimestampUs;
+      positionUs = timestampPositionUs + elapsedSinceTimestampUs;
     } else {
-      long positionUs;
       if (playheadOffsetCount == 0) {
         // The AudioTrack has started, but we don't have any samples to compute a smoothed position.
         positionUs = getPlaybackHeadPositionUs();
@@ -242,8 +251,29 @@ public long getCurrentPositionUs(boolean sourceEnded) {
       if (!sourceEnded) {
         positionUs = Math.max(0, positionUs - latencyUs);
       }
-      return positionUs;
     }
+
+    if (lastSampleUsedGetTimestampMode != useGetTimestampMode) {
+      // We've switched sampling mode.
+      previousModeSystemTimeUs = lastSystemTimeUs;
+      previousModePositionUs = lastPositionUs;
+    }
+    long elapsedSincePreviousModeUs = systemTimeUs - previousModeSystemTimeUs;
+    if (elapsedSincePreviousModeUs < MODE_SWITCH_SMOOTHING_DURATION_US) {
+      // Use a ramp to smooth between the old mode and the new one to avoid introducing a sudden
+      // jump if the two modes disagree.
+      long previousModeProjectedPositionUs = previousModePositionUs + elapsedSincePreviousModeUs;
+      // A ramp consisting of 1000 points distributed over MODE_SWITCH_SMOOTHING_DURATION_US.
+      long rampPoint = (elapsedSincePreviousModeUs * 1000) / MODE_SWITCH_SMOOTHING_DURATION_US;
+      positionUs *= rampPoint;
+      positionUs += (1000 - rampPoint) * previousModeProjectedPositionUs;
+      positionUs /= 1000;
+    }
+
+    lastSystemTimeUs = systemTimeUs;
+    lastPositionUs = positionUs;
+    lastSampleUsedGetTimestampMode = useGetTimestampMode;
+    return positionUs;
   }
 
   /** Starts position tracking. Must be called immediately before {@link AudioTrack#play()}. */
@@ -458,6 +488,8 @@ private void resetSyncParams() {
     playheadOffsetCount = 0;
     nextPlayheadOffsetIndex = 0;
     lastPlayheadSampleTimeUs = 0;
+    lastSystemTimeUs = 0;
+    previousModeSystemTimeUs = 0;
   }
 
   /**