Parse TLEN duration in Mp3Extractor

Issue: #7949
PiperOrigin-RevId: 333733615

RELEASENOTES.md

@@ -14,6 +14,8 @@
 *   Extractors:
     *   Add support for .mp2 boxes in the `AtomParsers`
         ([#7967](https://github.com/google/ExoPlayer/issues/7967)).
+    *   Use TLEN ID3 tag to compute the duration in Mp3Extractor
+        ([#7949](https://github.com/google/ExoPlayer/issues/7949)).
 
 ### 2.12.0 (2020-09-11) ###
 

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp3/MlltSeeker.java

@@ -29,9 +29,11 @@ import com.google.android.exoplayer2.util.Util;
    *
    * @param firstFramePosition The position of the start of the first frame in the stream.
    * @param mlltFrame The MLLT frame with seeking metadata.
+   * @param durationUs The stream duration in microseconds, or {@link C#TIME_UNSET} if it is
+   *     unknown.
    * @return An {@link MlltSeeker} for seeking in the stream.
    */
-  public static MlltSeeker create(long firstFramePosition, MlltFrame mlltFrame) {
+  public static MlltSeeker create(long firstFramePosition, MlltFrame mlltFrame, long durationUs) {
     int referenceCount = mlltFrame.bytesDeviations.length;
     long[] referencePositions = new long[1 + referenceCount];
     long[] referenceTimesMs = new long[1 + referenceCount];
@@ -45,19 +47,22 @@ import com.google.android.exoplayer2.util.Util;
       referencePositions[i] = position;
       referenceTimesMs[i] = timeMs;
     }
-    return new MlltSeeker(referencePositions, referenceTimesMs);
+    return new MlltSeeker(referencePositions, referenceTimesMs, durationUs);
   }
 
   private final long[] referencePositions;
   private final long[] referenceTimesMs;
   private final long durationUs;
 
-  private MlltSeeker(long[] referencePositions, long[] referenceTimesMs) {
+  private MlltSeeker(long[] referencePositions, long[] referenceTimesMs, long durationUs) {
     this.referencePositions = referencePositions;
     this.referenceTimesMs = referenceTimesMs;
-    // Use the last reference point as the duration, as extrapolating variable bitrate at the end of
+    // Use the last reference point as the duration if it is unknown, as extrapolating variable
-    // the stream may give a large error.
+    // bitrate at the end of the stream may give a large error.
-    durationUs = C.msToUs(referenceTimesMs[referenceTimesMs.length - 1]);
+    this.durationUs =
+        durationUs != C.TIME_UNSET
+            ? durationUs
+            : C.msToUs(referenceTimesMs[referenceTimesMs.length - 1]);
   }
 
   @Override

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp3/Mp3Extractor.java

@@ -35,6 +35,7 @@ import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.id3.Id3Decoder;
 import com.google.android.exoplayer2.metadata.id3.Id3Decoder.FramePredicate;
 import com.google.android.exoplayer2.metadata.id3.MlltFrame;
+import com.google.android.exoplayer2.metadata.id3.TextInformationFrame;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
@@ -432,7 +433,7 @@ public final class Mp3Extractor implements Extractor {
 
     @Nullable Seeker resultSeeker = null;
     if ((flags & FLAG_ENABLE_INDEX_SEEKING) != 0) {
-      long durationUs = C.TIME_UNSET;
+      long durationUs;
       long dataEndPosition = C.POSITION_UNSET;
       if (metadataSeeker != null) {
         durationUs = metadataSeeker.getDurationUs();
@@ -440,6 +441,8 @@ public final class Mp3Extractor implements Extractor {
       } else if (seekFrameSeeker != null) {
         durationUs = seekFrameSeeker.getDurationUs();
         dataEndPosition = seekFrameSeeker.getDataEndPosition();
+      } else {
+        durationUs = getId3TlenUs(metadata);
       }
       resultSeeker =
           new IndexSeeker(
@@ -554,10 +557,24 @@ public final class Mp3Extractor implements Extractor {
       for (int i = 0; i < length; i++) {
         Metadata.Entry entry = metadata.get(i);
         if (entry instanceof MlltFrame) {
-          return MlltSeeker.create(firstFramePosition, (MlltFrame) entry);
+          return MlltSeeker.create(firstFramePosition, (MlltFrame) entry, getId3TlenUs(metadata));
         }
       }
     }
     return null;
   }
+
+  private static long getId3TlenUs(@Nullable Metadata metadata) {
+    if (metadata != null) {
+      int length = metadata.length();
+      for (int i = 0; i < length; i++) {
+        Metadata.Entry entry = metadata.get(i);
+        if (entry instanceof TextInformationFrame
+            && ((TextInformationFrame) entry).id.equals("TLEN")) {
+          return C.msToUs(Long.parseLong(((TextInformationFrame) entry).value));
+        }
+      }
+    }
+    return C.TIME_UNSET;
+  }
 }