Add class to enable loading of out-of-band subtitle files.

library/src/main/java/com/google/android/exoplayer/chunk/SingleSampleChunkSource.java

+/*
+ * Copyright (C) 2014 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
+ *
+ *      http://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 com.google.android.exoplayer.chunk;
+
+import com.google.android.exoplayer.MediaFormat;
+import com.google.android.exoplayer.TrackInfo;
+import com.google.android.exoplayer.upstream.DataSource;
+import com.google.android.exoplayer.upstream.DataSpec;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * A chunk source that provides a single chunk containing a single sample.
+ * <p>
+ * An example use case for this implementation is to act as the source for loading out-of-band
+ * subtitles, where subtitles for the entire video are delivered as a single file.
+ */
+public class SingleSampleChunkSource implements ChunkSource {
+
+  private final DataSource dataSource;
+  private final DataSpec dataSpec;
+  private final Format format;
+  private final long durationUs;
+  private final MediaFormat mediaFormat;
+  private final TrackInfo trackInfo;
+
+  /**
+   * @param dataSource A {@link DataSource} suitable for loading the sample data.
+   * @param dataSpec Defines the location of the sample.
+   * @param format The format of the sample.
+   * @param durationUs The duration of the sample in microseconds.
+   * @param mediaFormat The sample media format. May be null.
+   */
+  public SingleSampleChunkSource(DataSource dataSource, DataSpec dataSpec, Format format,
+      long durationUs, MediaFormat mediaFormat) {
+    this.dataSource = dataSource;
+    this.dataSpec = dataSpec;
+    this.format = format;
+    this.durationUs = durationUs;
+    this.mediaFormat = mediaFormat;
+    trackInfo = new TrackInfo(format.mimeType, durationUs);
+  }
+
+  @Override
+  public TrackInfo getTrackInfo() {
+    return trackInfo;
+  }
+
+  @Override
+  public void getMaxVideoDimensions(MediaFormat out) {
+    // Do nothing.
+  }
+
+  @Override
+  public void enable() {
+    // Do nothing.
+  }
+
+  @Override
+  public void continueBuffering(long playbackPositionUs) {
+    // Do nothing.
+  }
+
+  @Override
+  public void getChunkOperation(List<? extends MediaChunk> queue, long seekPositionUs,
+      long playbackPositionUs, ChunkOperationHolder out) {
+    if (!queue.isEmpty()) {
+      // We've already provided the single sample.
+      return;
+    }
+    out.chunk = initChunk();
+  }
+
+  @Override
+  public void disable(List<? extends MediaChunk> queue) {
+    // Do nothing.
+  }
+
+  @Override
+  public IOException getError() {
+    return null;
+  }
+
+  @Override
+  public void onChunkLoadError(Chunk chunk, Exception e) {
+    // Do nothing.
+  }
+
+  private SingleSampleMediaChunk initChunk() {
+    return new SingleSampleMediaChunk(dataSource, dataSpec, format, 0, 0, durationUs, -1,
+        mediaFormat);
+  }
+
+}