SmoothStreaming fixes

- The -1 needs to be a 0. My bad.
- Create AAC CSD if not defined in manifest, like in V1.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131190995

library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/DefaultSsChunkSource.java

@@ -95,7 +95,7 @@ public class DefaultSsChunkSource implements SsChunkSource {
     for (int i = 0; i < extractorWrappers.length; i++) {
       int manifestTrackIndex = trackSelection.getIndexInTrackGroup(i);
       Format format = streamElement.formats[manifestTrackIndex];
-      int nalUnitLengthFieldLength = streamElement.type == C.TRACK_TYPE_VIDEO ? 4 : -1;
+      int nalUnitLengthFieldLength = streamElement.type == C.TRACK_TYPE_VIDEO ? 4 : 0;
       Track track = new Track(manifestTrackIndex, streamElement.type, streamElement.timescale,
           C.TIME_UNSET, manifest.durationUs, format, Track.TRANSFORMATION_NONE,
           trackEncryptionBoxes, nalUnitLengthFieldLength, null, null);

library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/manifest/SsManifestParser.java

@@ -633,6 +633,10 @@ public class SsManifestParser implements ParsingLoadable.Parser<SsManifest> {
         int samplingRate = parseRequiredInt(parser, KEY_SAMPLING_RATE);
         List<byte[]> codecSpecificData = buildCodecSpecificData(
             parser.getAttributeValue(null, KEY_CODEC_PRIVATE_DATA));
+        if (codecSpecificData.isEmpty() && MimeTypes.AUDIO_AAC.equals(sampleMimeType)) {
+          codecSpecificData = Collections.singletonList(
+              CodecSpecificDataUtil.buildAacLcAudioSpecificConfig(samplingRate, channels));
+        }
         String language = (String) getNormalizedAttribute(KEY_LANGUAGE);
         format = Format.createAudioContainerFormat(id, MimeTypes.AUDIO_MP4, sampleMimeType, null,
             bitrate, channels, samplingRate, codecSpecificData, 0, language);

library/src/main/java/com/google/android/exoplayer2/util/CodecSpecificDataUtil.java

@@ -67,6 +67,8 @@ public final class CodecSpecificDataUtil {
         AUDIO_SPECIFIC_CONFIG_CHANNEL_CONFIGURATION_INVALID
       };
 
+  // Advanced Audio Coding Low-Complexity profile.
+  private static final int AUDIO_OBJECT_TYPE_AAC_LC = 2;
   // Spectral Band Replication.
   private static final int AUDIO_OBJECT_TYPE_SBR = 5;
   // Error Resilient Bit-Sliced Arithmetic Coding.
@@ -118,6 +120,33 @@ public final class CodecSpecificDataUtil {
     return Pair.create(sampleRate, channelCount);
   }
 
+  /**
+   * 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.
+   * @return The AudioSpecificConfig.
+   */
+  public static byte[] buildAacLcAudioSpecificConfig(int sampleRate, int numChannels) {
+    int sampleRateIndex = C.INDEX_UNSET;
+    for (int i = 0; i < AUDIO_SPECIFIC_CONFIG_SAMPLING_RATE_TABLE.length; ++i) {
+      if (sampleRate == AUDIO_SPECIFIC_CONFIG_SAMPLING_RATE_TABLE[i]) {
+        sampleRateIndex = i;
+      }
+    }
+    int channelConfig = C.INDEX_UNSET;
+    for (int i = 0; i < AUDIO_SPECIFIC_CONFIG_CHANNEL_COUNT_TABLE.length; ++i) {
+      if (numChannels == AUDIO_SPECIFIC_CONFIG_CHANNEL_COUNT_TABLE[i]) {
+        channelConfig = i;
+      }
+    }
+    if (sampleRate == C.INDEX_UNSET || channelConfig == C.INDEX_UNSET) {
+      throw new IllegalArgumentException("Invalid sample rate or number of channels: "
+          + sampleRate + ", " + numChannels);
+    }
+    return buildAacAudioSpecificConfig(AUDIO_OBJECT_TYPE_AAC_LC, sampleRateIndex, channelConfig);
+  }
+
   /**
    * Builds a simple AudioSpecificConfig, as defined in ISO 14496-3 1.6.2.1
    *