Use bits/sec instead of bytes/sec for format bandwidth.

Why: This was a bad initial choice. Manifests typically define bandwidth in
bits/sec. If you divide by 8 then you're throwing away information due to
rounding. Unfortunately it turns out that SegmentTemplate based manifests
require you to be able to recall the bitrate exactly (because it's substituted
in during segment URL construction).

Medium term: We should consider converting all our bandwidth estimation
over to bits/sec as well.

Note1: Also changed Period id to be a string, to match the mpd spec.
Note2: Made small optimization in FormatEvaluator to not consider discarding
the first chunk (durationBeforeThisSegmentUs will always be negative, and even
in the error case where it's not, removing the first thunk should be an error).

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

@@ -31,7 +31,7 @@ public class Format {
 
     @Override
     public int compare(Format a, Format b) {
-      return b.bandwidth - a.bandwidth;
+      return b.bitrate - a.bitrate;
     }
 
   }
@@ -67,45 +67,37 @@ public class Format {
   public final int audioSamplingRate;
 
   /**
-   * The average bandwidth in bytes per second.
+   * The average bandwidth in bits per second.
    */
+  public final int bitrate;
+
+  /**
+   * The average bandwidth in bytes per second.
+   *
+   * @deprecated Use {@link #bitrate}. However note that the units of measurement are different.
+   */
+  @Deprecated
   public final int bandwidth;
 
   /**
-   * @deprecated Format identifiers are now strings.
-   *
    * @param id The format identifier.
    * @param mimeType The format mime type.
    * @param width The width of the video in pixels, or -1 for non-video formats.
    * @param height The height of the video in pixels, or -1 for non-video formats.
    * @param numChannels The number of audio channels, or -1 for non-audio formats.
    * @param audioSamplingRate The audio sampling rate in Hz, or -1 for non-audio formats.
-   * @param bandwidth The average bandwidth of the format in bytes per second.
+   * @param bitrate The average bandwidth of the format in bits per second.
-   */
-  @Deprecated
-  public Format(int id, String mimeType, int width, int height, int numChannels,
-      int audioSamplingRate, int bandwidth) {
-    this(String.valueOf(id), mimeType, width, height, numChannels, audioSamplingRate, bandwidth);
-  }
-
-  /**
-   * @param id The format identifier.
-   * @param mimeType The format mime type.
-   * @param width The width of the video in pixels, or -1 for non-video formats.
-   * @param height The height of the video in pixels, or -1 for non-video formats.
-   * @param numChannels The number of audio channels, or -1 for non-audio formats.
-   * @param audioSamplingRate The audio sampling rate in Hz, or -1 for non-audio formats.
-   * @param bandwidth The average bandwidth of the format in bytes per second.
    */
   public Format(String id, String mimeType, int width, int height, int numChannels,
-      int audioSamplingRate, int bandwidth) {
+      int audioSamplingRate, int bitrate) {
     this.id = Assertions.checkNotNull(id);
     this.mimeType = mimeType;
     this.width = width;
     this.height = height;
     this.numChannels = numChannels;
     this.audioSamplingRate = audioSamplingRate;
-    this.bandwidth = bandwidth;
+    this.bitrate = bitrate;
+    this.bandwidth = bitrate / 8;
   }
 
   /**

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

@@ -236,8 +236,8 @@ public interface FormatEvaluator {
           : queue.get(queue.size() - 1).endTimeUs - playbackPositionUs;
       Format current = evaluation.format;
       Format ideal = determineIdealFormat(formats, bandwidthMeter.getEstimate());
-      boolean isHigher = ideal != null && current != null && ideal.bandwidth > current.bandwidth;
+      boolean isHigher = ideal != null && current != null && ideal.bitrate > current.bitrate;
-      boolean isLower = ideal != null && current != null && ideal.bandwidth < current.bandwidth;
+      boolean isLower = ideal != null && current != null && ideal.bitrate < current.bitrate;
       if (isHigher) {
         if (bufferedDurationUs < minDurationForQualityIncreaseUs) {
           // The ideal format is a higher quality, but we have insufficient buffer to
@@ -247,11 +247,11 @@ public interface FormatEvaluator {
           // We're switching from an SD stream to a stream of higher resolution. Consider
           // discarding already buffered media chunks. Specifically, discard media chunks starting
           // from the first one that is of lower bandwidth, lower resolution and that is not HD.
-          for (int i = 0; i < queue.size(); i++) {
+          for (int i = 1; i < queue.size(); i++) {
             MediaChunk thisChunk = queue.get(i);
             long durationBeforeThisSegmentUs = thisChunk.startTimeUs - playbackPositionUs;
             if (durationBeforeThisSegmentUs >= minDurationToRetainAfterDiscardUs
-                && thisChunk.format.bandwidth < ideal.bandwidth
+                && thisChunk.format.bitrate < ideal.bitrate
                 && thisChunk.format.height < ideal.height
                 && thisChunk.format.height < 720
                 && thisChunk.format.width < 1280) {
@@ -280,7 +280,7 @@ public interface FormatEvaluator {
       long effectiveBandwidth = computeEffectiveBandwidthEstimate(bandwidthEstimate);
       for (int i = 0; i < formats.length; i++) {
         Format format = formats[i];
-        if (format.bandwidth <= effectiveBandwidth) {
+        if ((format.bitrate / 8) <= effectiveBandwidth) {
           return format;
         }
       }

library/src/main/java/com/google/android/exoplayer/dash/mpd/MediaPresentationDescriptionParser.java

@@ -111,7 +111,7 @@ public class MediaPresentationDescriptionParser extends DefaultHandler {
   private Period parsePeriod(XmlPullParser xpp, String contentId, Uri parentBaseUrl,
       long mediaPresentationDuration) throws XmlPullParserException, IOException {
     Uri baseUrl = parentBaseUrl;
-    int id = parseInt(xpp, "id");
+    String id = xpp.getAttributeValue(null, "id");
     long start = parseDurationMs(xpp, "start", 0);
     long duration = parseDurationMs(xpp, "duration", mediaPresentationDuration);
 
@@ -214,7 +214,7 @@ public class MediaPresentationDescriptionParser extends DefaultHandler {
       List<Segment.Timeline> segmentTimelineList) throws XmlPullParserException, IOException {
     Uri baseUrl = parentBaseUrl;
     String id = xpp.getAttributeValue(null, "id");
-    int bandwidth = parseInt(xpp, "bandwidth") / 8;
+    int bandwidth = parseInt(xpp, "bandwidth");
     int audioSamplingRate = parseInt(xpp, "audioSamplingRate");
     int width = parseInt(xpp, "width");
     int height = parseInt(xpp, "height");

library/src/main/java/com/google/android/exoplayer/dash/mpd/Period.java

@@ -23,7 +23,7 @@ import java.util.List;
  */
 public final class Period {
 
-  public final int id;
+  public final String id;
 
   public final long start;
 
@@ -39,16 +39,16 @@ public final class Period {
 
   public final long presentationTimeOffset;
 
-  public Period(int id, long start, long duration, List<AdaptationSet> adaptationSets) {
+  public Period(String id, long start, long duration, List<AdaptationSet> adaptationSets) {
     this(id, start, duration, adaptationSets, null, 0, 0, 0);
   }
 
-  public Period(int id, long start, long duration, List<AdaptationSet> adaptationSets,
+  public Period(String id, long start, long duration, List<AdaptationSet> adaptationSets,
       List<Segment.Timeline> segmentList, int segmentStartNumber, int segmentTimescale) {
     this(id, start, duration, adaptationSets, segmentList, segmentStartNumber, segmentTimescale, 0);
   }
 
-  public Period(int id, long start, long duration, List<AdaptationSet> adaptationSets,
+  public Period(String id, long start, long duration, List<AdaptationSet> adaptationSets,
       List<Segment.Timeline> segmentList, int segmentStartNumber, int segmentTimescale,
       long presentationTimeOffset) {
     this.id = id;

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

@@ -103,7 +103,7 @@ public class SmoothStreamingChunkSource implements ChunkSource {
       TrackElement trackElement = streamElement.tracks[trackIndex];
       formats[i] = new SmoothStreamingFormat(String.valueOf(trackIndex), trackElement.mimeType,
           trackElement.maxWidth, trackElement.maxHeight, trackElement.numChannels,
-          trackElement.sampleRate, trackElement.bitrate / 8, trackIndex);
+          trackElement.sampleRate, trackElement.bitrate, trackIndex);
       maxWidth = Math.max(maxWidth, trackElement.maxWidth);
       maxHeight = Math.max(maxHeight, trackElement.maxHeight);
 
@@ -266,8 +266,8 @@ public class SmoothStreamingChunkSource implements ChunkSource {
     public final int trackIndex;
 
     public SmoothStreamingFormat(String id, String mimeType, int width, int height,
-        int numChannels, int audioSamplingRate, int bandwidth, int trackIndex) {
+        int numChannels, int audioSamplingRate, int bitrate, int trackIndex) {
-      super(id, mimeType, width, height, numChannels, audioSamplingRate, bandwidth);
+      super(id, mimeType, width, height, numChannels, audioSamplingRate, bitrate);
       this.trackIndex = trackIndex;
     }