diff --git a/library/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java b/library/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
index 14265299d1..05a910e70f 100644
--- a/library/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
+++ b/library/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
@@ -314,6 +314,7 @@ import java.util.ArrayList;
     try {
       resetInternal();
       this.mediaSource = mediaSource;
+      mediaSource.prepareSource();
       setState(ExoPlayer.STATE_BUFFERING);
       handler.sendEmptyMessage(MSG_DO_SOME_WORK);
     } finally {
@@ -538,7 +539,10 @@ import java.util.ArrayList;
       }
     }
     enabledRenderers = new Renderer[0];
-    mediaSource = null;
+    if (mediaSource != null) {
+      mediaSource.releaseSource();
+      mediaSource = null;
+    }
     timeline.reset();
     loadControl.reset();
     setIsLoading(false);
@@ -654,7 +658,7 @@ import java.util.ArrayList;
             loadingPeriod = newPeriod;
             long startPositionUs = playingPeriod == null ? playbackInfo.positionUs : 0;
             setIsLoading(true);
-            loadingPeriod.mediaPeriod.prepare(ExoPlayerImplInternal.this,
+            loadingPeriod.mediaPeriod.preparePeriod(ExoPlayerImplInternal.this,
                 loadControl.getAllocator(), startPositionUs);
           }
         }
@@ -1096,7 +1100,7 @@ import java.util.ArrayList;
 
     public void release() {
       try {
-        mediaPeriod.release();
+        mediaPeriod.releasePeriod();
       } catch (RuntimeException e) {
         // There's nothing we can do.
         Log.e(TAG, "Period release failed.", e);
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
index 80da78c82e..00b6545654 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
@@ -29,6 +29,13 @@ public final class ConcatenatingMediaSource implements MediaSource {
     this.mediaSources = mediaSources;
   }
 
+  @Override
+  public void prepareSource() {
+    for (MediaSource mediaSource : mediaSources) {
+      mediaSource.prepareSource();
+    }
+  }
+
   @Override
   public int getPeriodCount() {
     int sourceCount = 0;
@@ -55,4 +62,11 @@ public final class ConcatenatingMediaSource implements MediaSource {
     throw new IndexOutOfBoundsException();
   }
 
+  @Override
+  public void releaseSource() {
+    for (MediaSource mediaSource : mediaSources) {
+      mediaSource.releaseSource();
+    }
+  }
+
 }
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java
index 8941a62def..bf3ee0f055 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java
@@ -186,6 +186,11 @@ public final class ExtractorMediaSource implements MediaPeriod, MediaSource,
 
   // MediaSource implementation.
 
+  @Override
+  public void prepareSource() {
+    // do nothing
+  }
+
   @Override
   public int getPeriodCount() {
     return 1;
@@ -197,10 +202,15 @@ public final class ExtractorMediaSource implements MediaPeriod, MediaSource,
     return this;
   }
 
+  @Override
+  public void releaseSource() {
+    // do nothing
+  }
+
   // MediaPeriod implementation.
 
   @Override
-  public void prepare(Callback callback, Allocator allocator, long positionUs) {
+  public void preparePeriod(Callback callback, Allocator allocator, long positionUs) {
     this.callback = callback;
     this.allocator = allocator;
 
@@ -345,7 +355,7 @@ public final class ExtractorMediaSource implements MediaPeriod, MediaSource,
   }
 
   @Override
-  public void release() {
+  public void releasePeriod() {
     dataSource = null;
     if (loader != null) {
       final ExtractorHolder extractorHolder = this.extractorHolder;
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/MediaPeriod.java b/library/src/main/java/com/google/android/exoplayer2/source/MediaPeriod.java
index cc7effab73..ee2a679e22 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/MediaPeriod.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/MediaPeriod.java
@@ -55,7 +55,7 @@ public interface MediaPeriod extends SequenceableLoader {
    * @param allocator An {@link Allocator} from which to obtain media buffer allocations.
    * @param positionUs The player's current playback position.
    */
-  void prepare(Callback callback, Allocator allocator, long positionUs);
+  void preparePeriod(Callback callback, Allocator allocator, long positionUs);
 
   /**
    * Throws an error that's preventing the period from becoming prepared. Does nothing if no such
@@ -149,6 +149,6 @@ public interface MediaPeriod extends SequenceableLoader {
    * This method should be called when the period is no longer required. It may be called in any
    * state.
    */
-  void release();
+  void releasePeriod();
 
 }
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/MediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/MediaSource.java
index b88fd3c997..e099c23a0d 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/MediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/MediaSource.java
@@ -25,6 +25,13 @@ public interface MediaSource {
    */
   int UNKNOWN_PERIOD_COUNT = -1;
 
+  /**
+   * Starts preparation of the source.
+   */
+  void prepareSource();
+
+  // TODO add void maybeThrowError() throws IOException;
+
   /**
    * Returns the number of periods in the source, or {@link #UNKNOWN_PERIOD_COUNT} if the number
    * of periods is not yet known.
@@ -42,4 +49,12 @@ public interface MediaSource {
    */
   MediaPeriod createPeriod(int index);
 
+  /**
+   * Releases the source.
+   * <p>
+   * This method should be called when the source is no longer required. It may be called in any
+   * state.
+   */
+  void releaseSource();
+
 }
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaPeriod.java b/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaPeriod.java
index 62f2ef1291..92dfb55c8f 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaPeriod.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaPeriod.java
@@ -52,10 +52,10 @@ public final class MergingMediaPeriod implements MediaPeriod, MediaPeriod.Callba
   }
 
   @Override
-  public void prepare(Callback callback, Allocator allocator, long positionUs) {
+  public void preparePeriod(Callback callback, Allocator allocator, long positionUs) {
     this.callback = callback;
     for (MediaPeriod period : periods) {
-      period.prepare(this, allocator, positionUs);
+      period.preparePeriod(this, allocator, positionUs);
     }
   }
 
@@ -157,9 +157,9 @@ public final class MergingMediaPeriod implements MediaPeriod, MediaPeriod.Callba
   }
 
   @Override
-  public void release() {
+  public void releasePeriod() {
     for (MediaPeriod period : periods) {
-      period.release();
+      period.releasePeriod();
     }
   }
 
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java
index dcd04e54be..691431eacf 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java
@@ -36,12 +36,19 @@ public final class MergingMediaSource implements MediaSource {
     periodCount = mediaSources[0].getPeriodCount();
     Assertions.checkState(periodCount != UNKNOWN_PERIOD_COUNT,
         "Child sources must have known period counts");
-    for (int i = 1; i < mediaSources.length; i++) {
-      Assertions.checkState(mediaSources[i].getPeriodCount() == periodCount,
+    for (MediaSource mediaSource : mediaSources) {
+      Assertions.checkState(mediaSource.getPeriodCount() == periodCount,
           "Child sources must have equal period counts");
     }
   }
 
+  @Override
+  public void prepareSource() {
+    for (MediaSource mediaSource : mediaSources) {
+      mediaSource.prepareSource();
+    }
+  }
+
   @Override
   public int getPeriodCount() {
     return periodCount;
@@ -57,4 +64,11 @@ public final class MergingMediaSource implements MediaSource {
     return new MergingMediaPeriod(periods);
   }
 
+  @Override
+  public void releaseSource() {
+    for (MediaSource mediaSource : mediaSources) {
+      mediaSource.releaseSource();
+    }
+  }
+
 }
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java
index db88ddec7b..85f099c790 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java
@@ -115,6 +115,11 @@ public final class SingleSampleMediaSource implements MediaPeriod, MediaSource,
 
   // MediaSource implementation.
 
+  @Override
+  public void prepareSource() {
+    // do nothing
+  }
+
   @Override
   public int getPeriodCount() {
     return 1;
@@ -126,10 +131,15 @@ public final class SingleSampleMediaSource implements MediaPeriod, MediaSource,
     return this;
   }
 
+  @Override
+  public void releaseSource() {
+    // do nothing
+  }
+
   // MediaPeriod implementation.
 
   @Override
-  public void prepare(Callback callback, Allocator allocator, long positionUs) {
+  public void preparePeriod(Callback callback, Allocator allocator, long positionUs) {
     loader = new Loader("Loader:SingleSampleMediaSource");
     callback.onPeriodPrepared(this);
   }
@@ -192,7 +202,7 @@ public final class SingleSampleMediaSource implements MediaPeriod, MediaSource,
   }
 
   @Override
-  public void release() {
+  public void releasePeriod() {
     if (loader != null) {
       loader.release();
       loader = null;
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java b/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java
index 83c8573421..43a7ae018c 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaPeriod.java
@@ -96,7 +96,7 @@ import java.util.List;
   // MediaPeriod implementation.
 
   @Override
-  public void prepare(Callback callback, Allocator allocator, long positionUs) {
+  public void preparePeriod(Callback callback, Allocator allocator, long positionUs) {
     this.callback = callback;
     this.allocator = allocator;
     sampleStreams = newSampleStreamArray(0);
@@ -188,7 +188,7 @@ import java.util.List;
   }
 
   @Override
-  public void release() {
+  public void releasePeriod() {
     if (sampleStreams != null) {
       for (ChunkSampleStream<DashChunkSource> sampleStream : sampleStreams) {
         sampleStream.release();
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
index ff582313e1..102d8daeb0 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
@@ -92,14 +92,12 @@ public final class DashMediaSource implements MediaSource {
     eventDispatcher = new EventDispatcher(eventHandler, eventListener);
     manifestParser = new MediaPresentationDescriptionParser();
     manifestCallback = new ManifestCallback();
-    // TODO: Remove this call when prepare() is a part of MediaSource.
-    prepare(dataSourceFactory);
   }
 
   // MediaSource implementation.
 
-  // TODO @Override
-  public void prepare(DataSourceFactory dataSourceFactory) {
+  @Override
+  public void prepareSource() {
     dataSource = dataSourceFactory.createDataSource();
     loader = new Loader("Loader:DashMediaSource");
     manifestRefreshHandler = new Handler();
@@ -122,8 +120,8 @@ public final class DashMediaSource implements MediaSource {
     return periods[index];
   }
 
-  // TODO @Override
-  public void release() {
+  @Override
+  public void releaseSource() {
     dataSource = null;
     if (loader != null) {
       loader.release();
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java
index 71596eae7f..f5a0c23a8b 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java
@@ -112,6 +112,11 @@ public final class HlsMediaSource implements MediaPeriod, MediaSource,
 
   // MediaSource implementation.
 
+  @Override
+  public void prepareSource() {
+    // do nothing
+  }
+
   @Override
   public int getPeriodCount() {
     return 1;
@@ -123,10 +128,15 @@ public final class HlsMediaSource implements MediaPeriod, MediaSource,
     return this;
   }
 
+  @Override
+  public void releaseSource() {
+    // do nothing
+  }
+
   // MediaPeriod implementation.
 
   @Override
-  public void prepare(Callback callback, Allocator allocator, long positionUs) {
+  public void preparePeriod(Callback callback, Allocator allocator, long positionUs) {
     this.callback = callback;
     this.allocator = allocator;
     preparePositionUs = positionUs;
@@ -228,7 +238,7 @@ public final class HlsMediaSource implements MediaPeriod, MediaSource,
   }
 
   @Override
-  public void release() {
+  public void releasePeriod() {
     sampleStreamSources.clear();
     timestampAdjusterProvider.reset();
     manifestDataSource = null;
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SmoothStreamingMediaSource.java b/library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SmoothStreamingMediaSource.java
index d900ca5779..4a5694c3ff 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SmoothStreamingMediaSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SmoothStreamingMediaSource.java
@@ -112,6 +112,11 @@ public final class SmoothStreamingMediaSource implements MediaPeriod, MediaSourc
 
   // MediaSource implementation.
 
+  @Override
+  public void prepareSource() {
+    // do nothing
+  }
+
   @Override
   public int getPeriodCount() {
     return 1;
@@ -123,10 +128,15 @@ public final class SmoothStreamingMediaSource implements MediaPeriod, MediaSourc
     return this;
   }
 
+  @Override
+  public void releaseSource() {
+    // do nothing
+  }
+
   // MediaPeriod implementation.
 
   @Override
-  public void prepare(Callback callback, Allocator allocator, long positionUs) {
+  public void preparePeriod(Callback callback, Allocator allocator, long positionUs) {
     this.callback = callback;
     this.allocator = allocator;
     sampleStreams = newSampleStreamArray(0);
@@ -218,7 +228,7 @@ public final class SmoothStreamingMediaSource implements MediaPeriod, MediaSourc
   }
 
   @Override
-  public void release() {
+  public void releasePeriod() {
     manifestDataSource = null;
     if (manifestLoader != null) {
       manifestLoader.release();