Use stable order for subtitle buffers with identical timestamps

Issue: #3782

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=185673731

RELEASENOTES.md

@@ -76,8 +76,12 @@
   * Support resampling 24-bit and 32-bit integer to 32-bit float for high
     resolution output in `DefaultAudioSink`
     ([#3635](https://github.com/google/ExoPlayer/pull/3635)).
-* Captions: Initial support for PGS subtitles
-  ([#3008](https://github.com/google/ExoPlayer/issues/3008)).
+* Captions:
+  * Initial support for PGS subtitles
+    ([#3008](https://github.com/google/ExoPlayer/issues/3008)).
+  * Fix issue handling CEA-608 captions where multiple buffers have the same
+    presentation timestamp
+    ([#3782](https://github.com/google/ExoPlayer/issues/3782)).
 * CacheDataSource: Check periodically if it's possible to read from/write to
   cache after deciding to bypass cache.
 * IMA extension:

library/core/src/main/java/com/google/android/exoplayer2/text/SubtitleInputBuffer.java

@@ -15,15 +15,11 @@
  */
 package com.google.android.exoplayer2.text;
 
-import android.support.annotation.NonNull;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
 
-/**
- * A {@link DecoderInputBuffer} for a {@link SubtitleDecoder}.
- */
-public final class SubtitleInputBuffer extends DecoderInputBuffer
-    implements Comparable<SubtitleInputBuffer> {
+/** A {@link DecoderInputBuffer} for a {@link SubtitleDecoder}. */
+public class SubtitleInputBuffer extends DecoderInputBuffer {
 
   /**
    * An offset that must be added to the subtitle's event times after it's been decoded, or
@@ -35,16 +31,4 @@ public SubtitleInputBuffer() {
     super(DecoderInputBuffer.BUFFER_REPLACEMENT_MODE_NORMAL);
   }
 
-  @Override
-  public int compareTo(@NonNull SubtitleInputBuffer other) {
-    if (isEndOfStream() != other.isEndOfStream()) {
-      return isEndOfStream() ? 1 : -1;
-    }
-    long delta = timeUs - other.timeUs;
-    if (delta == 0) {
-      return 0;
-    }
-    return delta > 0 ? 1 : -1;
-  }
-
 }

library/core/src/main/java/com/google/android/exoplayer2/text/cea/CeaDecoder.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.text.cea;
 
+import android.support.annotation.NonNull;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.text.Subtitle;
@@ -34,21 +35,22 @@
   private static final int NUM_INPUT_BUFFERS = 10;
   private static final int NUM_OUTPUT_BUFFERS = 2;
 
-  private final LinkedList<SubtitleInputBuffer> availableInputBuffers;
+  private final LinkedList<CeaInputBuffer> availableInputBuffers;
   private final LinkedList<SubtitleOutputBuffer> availableOutputBuffers;
-  private final PriorityQueue<SubtitleInputBuffer> queuedInputBuffers;
+  private final PriorityQueue<CeaInputBuffer> queuedInputBuffers;
 
-  private SubtitleInputBuffer dequeuedInputBuffer;
+  private CeaInputBuffer dequeuedInputBuffer;
   private long playbackPositionUs;
+  private long queuedInputBufferCount;
 
   public CeaDecoder() {
     availableInputBuffers = new LinkedList<>();
     for (int i = 0; i < NUM_INPUT_BUFFERS; i++) {
-      availableInputBuffers.add(new SubtitleInputBuffer());
+      availableInputBuffers.add(new CeaInputBuffer());
     }
     availableOutputBuffers = new LinkedList<>();
     for (int i = 0; i < NUM_OUTPUT_BUFFERS; i++) {
-      availableOutputBuffers.add(new CeaOutputBuffer(this));
+      availableOutputBuffers.add(new CeaOutputBuffer());
     }
     queuedInputBuffers = new PriorityQueue<>();
   }
@@ -77,9 +79,10 @@ public void queueInputBuffer(SubtitleInputBuffer inputBuffer) throws SubtitleDec
     if (inputBuffer.isDecodeOnly()) {
       // We can drop this buffer early (i.e. before it would be decoded) as the CEA formats allow
       // for decoding to begin mid-stream.
-      releaseInputBuffer(inputBuffer);
+      releaseInputBuffer(dequeuedInputBuffer);
     } else {
-      queuedInputBuffers.add(inputBuffer);
+      dequeuedInputBuffer.queuedInputBufferCount = queuedInputBufferCount++;
+      queuedInputBuffers.add(dequeuedInputBuffer);
     }
     dequeuedInputBuffer = null;
   }
@@ -94,7 +97,7 @@ public SubtitleOutputBuffer dequeueOutputBuffer() throws SubtitleDecoderExceptio
     // be deferred until they would be applicable
     while (!queuedInputBuffers.isEmpty()
         && queuedInputBuffers.peek().timeUs <= playbackPositionUs) {
-      SubtitleInputBuffer inputBuffer = queuedInputBuffers.poll();
+      CeaInputBuffer inputBuffer = queuedInputBuffers.poll();
 
       // If the input buffer indicates we've reached the end of the stream, we can
       // return immediately with an output buffer propagating that
@@ -126,7 +129,7 @@ public SubtitleOutputBuffer dequeueOutputBuffer() throws SubtitleDecoderExceptio
     return null;
   }
 
-  private void releaseInputBuffer(SubtitleInputBuffer inputBuffer) {
+  private void releaseInputBuffer(CeaInputBuffer inputBuffer) {
     inputBuffer.clear();
     availableInputBuffers.add(inputBuffer);
   }
@@ -138,6 +141,7 @@ protected void releaseOutputBuffer(SubtitleOutputBuffer outputBuffer) {
 
   @Override
   public void flush() {
+    queuedInputBufferCount = 0;
     playbackPositionUs = 0;
     while (!queuedInputBuffers.isEmpty()) {
       releaseInputBuffer(queuedInputBuffers.poll());
@@ -169,4 +173,32 @@ public void release() {
    */
   protected abstract void decode(SubtitleInputBuffer inputBuffer);
 
+  private static final class CeaInputBuffer extends SubtitleInputBuffer
+      implements Comparable<CeaInputBuffer> {
+
+    private long queuedInputBufferCount;
+
+    @Override
+    public int compareTo(@NonNull CeaInputBuffer other) {
+      if (isEndOfStream() != other.isEndOfStream()) {
+        return isEndOfStream() ? 1 : -1;
+      }
+      long delta = timeUs - other.timeUs;
+      if (delta == 0) {
+        delta = queuedInputBufferCount - other.queuedInputBufferCount;
+        if (delta == 0) {
+          return 0;
+        }
+      }
+      return delta > 0 ? 1 : -1;
+    }
+  }
+
+  private final class CeaOutputBuffer extends SubtitleOutputBuffer {
+
+    @Override
+    public final void release() {
+      releaseOutputBuffer(this);
+    }
+  }
 }