Call FormatHolder what it really is.

Since we have a Format class as well, it's very confusing that
FormatHolder actually holds a MediaFormat. I think it's quite
likely that Format will need promoting into the root package as
part of the HLS work, which will make this even more confusing
(although it is possible that for HLS we'll define yet another
Format class, if it turns out we need significantly different
fields).

Note - I deliberately avoided renaming the formatHolder
args/params, because they're not particularly ambiguous and
because it introduces some ugly line breaks.

library/src/main/java/com/google/android/exoplayer/FrameworkSampleSource.java

@@ -112,7 +112,7 @@ public final class FrameworkSampleSource implements SampleSource {
   }
 
   @Override
-  public int readData(int track, long playbackPositionUs, FormatHolder formatHolder,
+  public int readData(int track, long playbackPositionUs, MediaFormatHolder formatHolder,
       SampleHolder sampleHolder, boolean onlyReadDiscontinuity) {
     Assertions.checkState(prepared);
     Assertions.checkState(trackStates[track] != TRACK_STATE_DISABLED);

library/src/main/java/com/google/android/exoplayer/MediaCodecTrackRenderer.java

@@ -124,7 +124,7 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
   private final boolean playClearSamplesWithoutKeys;
   private final SampleSource source;
   private final SampleHolder sampleHolder;
-  private final FormatHolder formatHolder;
+  private final MediaFormatHolder formatHolder;
   private final HashSet<Long> decodeOnlyPresentationTimestamps;
   private final MediaCodec.BufferInfo outputBufferInfo;
   private final EventListener eventListener;
@@ -174,7 +174,7 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
     this.eventListener = eventListener;
     codecCounters = new CodecCounters();
     sampleHolder = new SampleHolder(false);
-    formatHolder = new FormatHolder();
+    formatHolder = new MediaFormatHolder();
     decodeOnlyPresentationTimestamps = new HashSet<Long>();
     outputBufferInfo = new MediaCodec.BufferInfo();
   }
@@ -619,7 +619,7 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
    * @param formatHolder Holds the new format.
    * @throws ExoPlaybackException If an error occurs reinitializing the {@link MediaCodec}.
    */
-  private void onInputFormatChanged(FormatHolder formatHolder) throws ExoPlaybackException {
+  private void onInputFormatChanged(MediaFormatHolder formatHolder) throws ExoPlaybackException {
     MediaFormat oldFormat = format;
     format = formatHolder.format;
     drmInitData = formatHolder.drmInitData;

library/src/main/java/com/google/android/exoplayer/MediaFormat.java

@@ -27,7 +27,7 @@ import java.util.Collections;
 import java.util.List;
 
 /**
- * Encapsulates the information describing the format of media data, be it audio or video.
+ * Defines the format of an elementary media stream.
  */
 public class MediaFormat {
 

library/src/main/java/com/google/android/exoplayer/MediaFormatHolder.java

@@ -21,7 +21,7 @@ import java.util.UUID;
 /**
  * Holds a {@link MediaFormat} and corresponding drm scheme initialization data.
  */
-public final class FormatHolder {
+public final class MediaFormatHolder {
 
   /**
    * The format of the media.

library/src/main/java/com/google/android/exoplayer/SampleSource.java

@@ -80,7 +80,7 @@ public interface SampleSource {
 
   /**
    * Enable the specified track. This allows the track's format and samples to be read from
-   * {@link #readData(int, long, FormatHolder, SampleHolder, boolean)}.
+   * {@link #readData(int, long, MediaFormatHolder, SampleHolder, boolean)}.
    * <p>
    * This method should not be called until after the source has been successfully prepared.
    *
@@ -119,7 +119,7 @@ public interface SampleSource {
    *
    * @param track The track from which to read.
    * @param playbackPositionUs The current playback position.
-   * @param formatHolder A {@link FormatHolder} object to populate in the case of a new format.
+   * @param formatHolder A {@link MediaFormatHolder} object to populate in the case of a new format.
    * @param sampleHolder A {@link SampleHolder} object to populate in the case of a new sample. If
    *     the caller requires the sample data then it must ensure that {@link SampleHolder#data}
    *     references a valid output buffer.
@@ -129,7 +129,7 @@ public interface SampleSource {
    *     {@link #DISCONTINUITY_READ}, {@link #NOTHING_READ} or {@link #END_OF_STREAM}.
    * @throws IOException If an error occurred reading from the source.
    */
-  public int readData(int track, long playbackPositionUs, FormatHolder formatHolder,
+  public int readData(int track, long playbackPositionUs, MediaFormatHolder formatHolder,
       SampleHolder sampleHolder, boolean onlyReadDiscontinuity) throws IOException;
 
   /**

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

@@ -16,9 +16,9 @@
 package com.google.android.exoplayer.chunk;
 
 import com.google.android.exoplayer.C;
-import com.google.android.exoplayer.FormatHolder;
 import com.google.android.exoplayer.LoadControl;
 import com.google.android.exoplayer.MediaFormat;
+import com.google.android.exoplayer.MediaFormatHolder;
 import com.google.android.exoplayer.SampleHolder;
 import com.google.android.exoplayer.SampleSource;
 import com.google.android.exoplayer.TrackInfo;
@@ -267,7 +267,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
   }
 
   @Override
-  public int readData(int track, long playbackPositionUs, FormatHolder formatHolder,
+  public int readData(int track, long playbackPositionUs, MediaFormatHolder formatHolder,
       SampleHolder sampleHolder, boolean onlyReadDiscontinuity) throws IOException {
     Assertions.checkState(state == STATE_ENABLED);
     Assertions.checkState(track == 0);

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

@@ -20,7 +20,7 @@ import com.google.android.exoplayer.util.Assertions;
 import java.util.Comparator;
 
 /**
- * A format definition for streams.
+ * Defines the high level format of a media stream.
  */
 public class Format {
 

library/src/main/java/com/google/android/exoplayer/parser/mp4/FragmentedMp4Extractor.java

@@ -23,6 +23,7 @@ import com.google.android.exoplayer.parser.mp4.Atom.ContainerAtom;
 import com.google.android.exoplayer.parser.mp4.Atom.LeafAtom;
 import com.google.android.exoplayer.upstream.NonBlockingInputStream;
 import com.google.android.exoplayer.util.Assertions;
+import com.google.android.exoplayer.util.CodecSpecificDataUtil;
 import com.google.android.exoplayer.util.MimeTypes;
 
 import android.annotation.SuppressLint;

library/src/main/java/com/google/android/exoplayer/smoothstreaming/SmoothStreamingChunkSource.java

@@ -26,7 +26,6 @@ import com.google.android.exoplayer.chunk.FormatEvaluator;
 import com.google.android.exoplayer.chunk.FormatEvaluator.Evaluation;
 import com.google.android.exoplayer.chunk.MediaChunk;
 import com.google.android.exoplayer.chunk.Mp4MediaChunk;
-import com.google.android.exoplayer.parser.mp4.CodecSpecificDataUtil;
 import com.google.android.exoplayer.parser.mp4.FragmentedMp4Extractor;
 import com.google.android.exoplayer.parser.mp4.Track;
 import com.google.android.exoplayer.parser.mp4.TrackEncryptionBox;
@@ -35,6 +34,7 @@ import com.google.android.exoplayer.smoothstreaming.SmoothStreamingManifest.Stre
 import com.google.android.exoplayer.smoothstreaming.SmoothStreamingManifest.TrackElement;
 import com.google.android.exoplayer.upstream.DataSource;
 import com.google.android.exoplayer.upstream.DataSpec;
+import com.google.android.exoplayer.util.CodecSpecificDataUtil;
 
 import android.net.Uri;
 import android.util.Base64;

library/src/main/java/com/google/android/exoplayer/smoothstreaming/SmoothStreamingManifestParser.java

@@ -16,11 +16,11 @@
 package com.google.android.exoplayer.smoothstreaming;
 
 import com.google.android.exoplayer.ParserException;
-import com.google.android.exoplayer.parser.mp4.CodecSpecificDataUtil;
 import com.google.android.exoplayer.smoothstreaming.SmoothStreamingManifest.ProtectionElement;
 import com.google.android.exoplayer.smoothstreaming.SmoothStreamingManifest.StreamElement;
 import com.google.android.exoplayer.smoothstreaming.SmoothStreamingManifest.TrackElement;
 import com.google.android.exoplayer.util.Assertions;
+import com.google.android.exoplayer.util.CodecSpecificDataUtil;
 
 import android.util.Base64;
 import android.util.Pair;

library/src/main/java/com/google/android/exoplayer/text/TextTrackRenderer.java

@@ -16,7 +16,7 @@
 package com.google.android.exoplayer.text;
 
 import com.google.android.exoplayer.ExoPlaybackException;
-import com.google.android.exoplayer.FormatHolder;
+import com.google.android.exoplayer.MediaFormatHolder;
 import com.google.android.exoplayer.SampleHolder;
 import com.google.android.exoplayer.SampleSource;
 import com.google.android.exoplayer.TrackRenderer;
@@ -64,7 +64,7 @@ public class TextTrackRenderer extends TrackRenderer implements Callback {
   private final TextRenderer textRenderer;
   private final SampleSource source;
   private final SampleHolder sampleHolder;
-  private final FormatHolder formatHolder;
+  private final MediaFormatHolder formatHolder;
   private final SubtitleParser subtitleParser;
 
   private int trackIndex;
@@ -93,7 +93,7 @@ public class TextTrackRenderer extends TrackRenderer implements Callback {
     this.textRenderer = Assertions.checkNotNull(textRenderer);
     this.textRendererHandler = textRendererLooper == null ? null : new Handler(textRendererLooper,
         this);
-    formatHolder = new FormatHolder();
+    formatHolder = new MediaFormatHolder();
     sampleHolder = new SampleHolder(true);
   }
 

library/src/main/java/com/google/android/exoplayer/util/CodecSpecificDataUtil.java

@@ -13,9 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package com.google.android.exoplayer.parser.mp4;
+package com.google.android.exoplayer.util;
-
-import com.google.android.exoplayer.util.Assertions;
 
 import android.annotation.SuppressLint;
 import android.media.MediaCodecInfo.CodecProfileLevel;
@@ -35,6 +33,10 @@ public final class CodecSpecificDataUtil {
     96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350
   };
 
+  private static final int[] AUDIO_SPECIFIC_CONFIG_CHANNEL_COUNT_TABLE = new int[] {
+    0, 1, 2, 3, 4, 5, 6, 8
+  };
+
   private static final int SPS_NAL_UNIT_TYPE = 7;
 
   private CodecSpecificDataUtil() {}
@@ -42,7 +44,7 @@ public final class CodecSpecificDataUtil {
   /**
    * Parses an AudioSpecificConfig, as defined in ISO 14496-3 1.6.2.1
    *
-   * @param audioSpecificConfig
+   * @param audioSpecificConfig The AudioSpecificConfig to parse.
    * @return A pair consisting of the sample rate in Hz and the channel count.
    */
   public static Pair<Integer, Integer> parseAudioSpecificConfig(byte[] audioSpecificConfig) {
@@ -56,11 +58,27 @@ public final class CodecSpecificDataUtil {
     return Pair.create(sampleRate, channelCount);
   }
 
+  /**
+   * Builds a simple AudioSpecificConfig, as defined in ISO 14496-3 1.6.2.1
+   *
+   * @param audioObjectType The audio object type.
+   * @param sampleRateIndex The sample rate index.
+   * @param channelConfig The channel configuration.
+   * @return The AudioSpecificConfig.
+   */
+  public static byte[] buildAudioSpecificConfig(int audioObjectType, int sampleRateIndex,
+      int channelConfig) {
+    byte[] audioSpecificConfig = new byte[2];
+    audioSpecificConfig[0] = (byte) ((audioObjectType << 3) & 0xF8 | (sampleRateIndex >> 1) & 0x07);
+    audioSpecificConfig[1] = (byte) ((sampleRateIndex << 7) & 0x80 | (channelConfig << 3) & 0x78);
+    return audioSpecificConfig;
+  }
+
   /**
    * Builds a simple HE-AAC LC AudioSpecificConfig, as defined in ISO 14496-3 1.6.2.1
    *
    * @param sampleRate The sample rate in Hz.
-   * @param numChannels The number of channels
+   * @param numChannels The number of channels.
    * @return The AudioSpecificConfig.
    */
   public static byte[] buildAudioSpecificConfig(int sampleRate, int numChannels) {
@@ -70,10 +88,16 @@ public final class CodecSpecificDataUtil {
         sampleRateIndex = i;
       }
     }
+    int channelConfig = -1;
+    for (int i = 0; i < AUDIO_SPECIFIC_CONFIG_CHANNEL_COUNT_TABLE.length; ++i) {
+      if (numChannels == AUDIO_SPECIFIC_CONFIG_CHANNEL_COUNT_TABLE[i]) {
+        channelConfig = i;
+      }
+    }
     // The full specification for AudioSpecificConfig is stated in ISO 14496-3 Section 1.6.2.1
     byte[] csd = new byte[2];
     csd[0] = (byte) ((2 /* AAC LC */ << 3) | (sampleRateIndex >> 1));
-    csd[1] = (byte) (((sampleRateIndex & 0x1) << 7) | (numChannels << 3));
+    csd[1] = (byte) (((sampleRateIndex & 0x1) << 7) | (channelConfig << 3));
     return csd;
   }