Simplify Mp4ExtractorWrapper implementation

Changes includes:
1. Create static factory method and hide constructor.
2. Move all the fetching logic to init() method.

PiperOrigin-RevId: 576544902

libraries/transformer/src/main/java/androidx/media3/transformer/Mp4MetadataInfo.java

@@ -38,39 +38,39 @@ import java.util.HashMap;
 import java.util.Map;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
-/** A wrapper around an {@link Mp4Extractor} providing methods to extract MP4 metadata. */
+/** Provides MP4 metadata like duration, last sync sample timestamp etc. */
-/* package */ final class Mp4ExtractorWrapper {
+/* package */ final class Mp4MetadataInfo {
-  private final Context context;
+  /**
-  private final String filePath;
+   * The duration (in microseconds) of the MP4 file or {@link C#TIME_UNSET} if the duration is
-  private final Mp4Extractor mp4Extractor;
+   * unknown.
-  private final ExtractorOutputImpl extractorOutput;
+   */
-  private boolean initialized;
+  public final long durationUs;
 
   /**
-   * Creates an instance.
+   * The presentation timestamp (in microseconds) of the last sync sample or {@link C#TIME_UNSET} if
-   *
+   * there is no video track.
-   * @param context A {@link Context}.
-   * @param filePath The file path of a valid MP4.
    */
-  public Mp4ExtractorWrapper(Context context, String filePath) {
+  public final long lastSyncSampleTimestampUs;
-    this.context = context;
+
-    this.filePath = filePath;
+  private Mp4MetadataInfo(long durationUs, long lastSyncSampleTimestampUs) {
-    mp4Extractor = new Mp4Extractor();
+    this.durationUs = durationUs;
-    extractorOutput = new ExtractorOutputImpl();
+    this.lastSyncSampleTimestampUs = lastSyncSampleTimestampUs;
   }
 
   /**
-   * Initializes the {@link Mp4ExtractorWrapper}.
+   * Extracts the MP4 metadata synchronously and returns {@link Mp4MetadataInfo}.
    *
-   * <p>This method must be called only once and it should be called before calling any other
+   * @param context A {@link Context}.
-   * method.
+   * @param filePath The file path of a valid MP4.
+   * @throws IOException If an error occurs during metadata extraction.
    */
-  public void init() throws IOException {
+  public static Mp4MetadataInfo create(Context context, String filePath) throws IOException {
-    checkState(!initialized);
+    Mp4Extractor mp4Extractor = new Mp4Extractor();
-
+    ExtractorOutputImpl extractorOutput = new ExtractorOutputImpl();
     DefaultDataSource dataSource =
         new DefaultDataSource(context, /* allowCrossProtocolRedirects= */ false);
     DataSpec dataSpec = new DataSpec.Builder().setUri(filePath).build();
+    try {
       long length = dataSource.open(dataSpec);
       checkState(length != 0);
       DefaultExtractorInput extractorInput =
@@ -79,7 +79,6 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 
       mp4Extractor.init(extractorOutput);
       PositionHolder positionHolder = new PositionHolder();
-    try {
       while (!extractorOutput.seekMapInitialized) {
         @Extractor.ReadResult int result = mp4Extractor.read(extractorInput, positionHolder);
         if (result == Extractor.RESULT_SEEK) {
@@ -98,27 +97,22 @@ import org.checkerframework.checker.nullness.qual.Nullable;
           throw new IllegalStateException("The MP4 file is invalid");
         }
       }
-      initialized = true;
-    } finally {
-      DataSourceUtil.closeQuietly(dataSource);
-    }
-  }
 
-  /**
-   * Returns the presentation timestamp (in microseconds) of the last sync sample or {@link
-   * C#TIME_UNSET} if there is no video track.
-   */
-  public long getLastSyncSampleTimestampUs() {
-    checkState(initialized);
-
-    if (extractorOutput.videoTrackId == C.INDEX_UNSET) {
-      return C.TIME_UNSET;
-    }
       long durationUs = mp4Extractor.getDurationUs();
+      long lastSyncSampleTimestampUs = C.TIME_UNSET;
+
+      // Fetch last sync sample timestamp.
+      if (extractorOutput.videoTrackId != C.INDEX_UNSET) {
         checkState(durationUs != C.TIME_UNSET);
         SeekMap.SeekPoints seekPoints =
             mp4Extractor.getSeekPoints(durationUs, extractorOutput.videoTrackId);
-    return seekPoints.first.timeUs;
+        lastSyncSampleTimestampUs = seekPoints.first.timeUs;
+      }
+      return new Mp4MetadataInfo(durationUs, lastSyncSampleTimestampUs);
+    } finally {
+      DataSourceUtil.closeQuietly(dataSource);
+      mp4Extractor.release();
+    }
   }
 
   private static final class ExtractorOutputImpl implements ExtractorOutput {
@@ -127,7 +121,7 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 
     private final Map<Integer, TrackOutput> trackTypeToTrackOutput;
 
-    ExtractorOutputImpl() {
+    public ExtractorOutputImpl() {
       videoTrackId = C.INDEX_UNSET;
       trackTypeToTrackOutput = new HashMap<>();
     }
@@ -159,7 +153,7 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 
       private final byte[] byteArray;
 
-      private TrackOutputImpl() {
+      public TrackOutputImpl() {
         byteArray = new byte[FIXED_BYTE_ARRAY_SIZE];
       }
 

libraries/transformer/src/test/java/androidx/media3/transformer/Mp4ExtractorWrapperTest.java

@@ -1,88 +0,0 @@
-/*
- * Copyright 2023 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package androidx.media3.transformer;
-
-import static com.google.common.truth.Truth.assertThat;
-import static org.junit.Assert.assertThrows;
-
-import android.content.Context;
-import androidx.media3.common.C;
-import androidx.test.core.app.ApplicationProvider;
-import androidx.test.ext.junit.runners.AndroidJUnit4;
-import java.io.IOException;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.TemporaryFolder;
-import org.junit.runner.RunWith;
-
-/** Unit tests for {@link Mp4ExtractorWrapper}. */
-@RunWith(AndroidJUnit4.class)
-public class Mp4ExtractorWrapperTest {
-  @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
-
-  private final Context context = ApplicationProvider.getApplicationContext();
-
-  @Test
-  public void init_withEmptyFile_throws() throws IOException {
-    String emptyFilePath = temporaryFolder.newFile("EmptyFile").getPath();
-    Mp4ExtractorWrapper mp4ExtractorWrapper = new Mp4ExtractorWrapper(context, emptyFilePath);
-
-    assertThrows(IllegalStateException.class, mp4ExtractorWrapper::init);
-  }
-
-  @Test
-  public void init_withNonMp4File_throws() {
-    String mp4FilePath = "asset:///media/mkv/sample.mkv";
-    Mp4ExtractorWrapper mp4ExtractorWrapper = new Mp4ExtractorWrapper(context, mp4FilePath);
-
-    assertThrows(IllegalStateException.class, mp4ExtractorWrapper::init);
-  }
-
-  @Test
-  public void getLastSyncSampleTimestampUs_ofSmallMp4File_outputsFirstTimestamp()
-      throws IOException {
-    String mp4FilePath = "asset:///media/mp4/sample.mp4";
-    Mp4ExtractorWrapper mp4ExtractorWrapper = new Mp4ExtractorWrapper(context, mp4FilePath);
-    mp4ExtractorWrapper.init();
-
-    long lastSyncSampleTimeStampUs = mp4ExtractorWrapper.getLastSyncSampleTimestampUs();
-
-    long expectedTimestamp = 0;
-    assertThat(lastSyncSampleTimeStampUs).isEqualTo(expectedTimestamp);
-  }
-
-  @Test
-  public void getLastSyncSampleTimestampUs_ofMp4File_outputMatchesExpected() throws IOException {
-    String mp4FilePath = "asset:///media/mp4/hdr10-720p.mp4";
-    Mp4ExtractorWrapper mp4ExtractorWrapper = new Mp4ExtractorWrapper(context, mp4FilePath);
-    mp4ExtractorWrapper.init();
-
-    long lastSyncSampleTimeStampUs = mp4ExtractorWrapper.getLastSyncSampleTimestampUs();
-
-    long expectedTimestamp = 4_003_277L;
-    assertThat(lastSyncSampleTimeStampUs).isEqualTo(expectedTimestamp);
-  }
-
-  @Test
-  public void getLastSyncSampleTimestampUs_ofAudioOnlyMp4File_returnsUnsetValue()
-      throws IOException {
-    String mp4FilePath = "asset:///media/mp4/sample_ac3.mp4";
-    Mp4ExtractorWrapper mp4ExtractorWrapper = new Mp4ExtractorWrapper(context, mp4FilePath);
-    mp4ExtractorWrapper.init();
-
-    assertThat(mp4ExtractorWrapper.getLastSyncSampleTimestampUs()).isEqualTo(C.TIME_UNSET);
-  }
-}

libraries/transformer/src/test/java/androidx/media3/transformer/Mp4MetadataInfoTest.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package androidx.media3.transformer;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
+
+import android.content.Context;
+import androidx.media3.common.C;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import java.io.IOException;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+
+/** Unit tests for {@link Mp4MetadataInfo}. */
+@RunWith(AndroidJUnit4.class)
+public class Mp4MetadataInfoTest {
+  @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+  private final Context context = ApplicationProvider.getApplicationContext();
+
+  @Test
+  public void create_withEmptyFile_throws() throws IOException {
+    String emptyFilePath = temporaryFolder.newFile("EmptyFile").getPath();
+
+    assertThrows(IllegalStateException.class, () -> Mp4MetadataInfo.create(context, emptyFilePath));
+  }
+
+  @Test
+  public void create_withNonMp4File_throws() {
+    String nonMp4FilePath = "asset:///media/mkv/sample.mkv";
+
+    assertThrows(
+        IllegalStateException.class, () -> Mp4MetadataInfo.create(context, nonMp4FilePath));
+  }
+
+  @Test
+  public void lastSyncSampleTimestampUs_ofSmallMp4File_outputsFirstTimestamp() throws IOException {
+    String mp4FilePath = "asset:///media/mp4/sample.mp4";
+    Mp4MetadataInfo mp4MetadataInfo = Mp4MetadataInfo.create(context, mp4FilePath);
+
+    assertThat(mp4MetadataInfo.lastSyncSampleTimestampUs)
+        .isEqualTo(0); // The timestamp of the first sample in sample.mp4.
+  }
+
+  @Test
+  public void lastSyncSampleTimestampUs_ofMp4File_outputMatchesExpected() throws IOException {
+    String mp4FilePath = "asset:///media/mp4/hdr10-720p.mp4";
+    Mp4MetadataInfo mp4MetadataInfo = Mp4MetadataInfo.create(context, mp4FilePath);
+
+    assertThat(mp4MetadataInfo.lastSyncSampleTimestampUs)
+        .isEqualTo(4_003_277L); // The timestamp of the last sync sample in hdr10-720p.mp4.
+  }
+
+  @Test
+  public void lastSyncSampleTimestampUs_ofAudioOnlyMp4File_isUnset() throws IOException {
+    String audioOnlyMp4FilePath = "asset:///media/mp4/sample_ac3.mp4";
+    Mp4MetadataInfo mp4MetadataInfo = Mp4MetadataInfo.create(context, audioOnlyMp4FilePath);
+
+    assertThat(mp4MetadataInfo.lastSyncSampleTimestampUs).isEqualTo(C.TIME_UNSET);
+  }
+
+  @Test
+  public void durationUs_ofMp4File_outputMatchesExpected() throws Exception {
+    String mp4FilePath = "asset:///media/mp4/hdr10-720p.mp4";
+    Mp4MetadataInfo mp4MetadataInfo = Mp4MetadataInfo.create(context, mp4FilePath);
+
+    assertThat(mp4MetadataInfo.durationUs).isEqualTo(4_236_600L); // The duration of hdr10-720p.mp4.
+  }
+}