Use AVERAGE-BANDWIDTH instead of BANDWIDTH when available

Also prevent BANDWIDTH's regex from matching the AVERAGE-BANDWIDTH attribute.

Issue:#2863

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=157219453

library/hls/src/androidTest/java/com/google/android/exoplayer2/source/hls/playlist/HlsMasterPlaylistParserTest.java

@@ -51,6 +51,15 @@ public class HlsMasterPlaylistParserTest extends TestCase {
       + "#EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS=\"mp4a.40.5\"\n"
       + "http://example.com/audio-only.m3u8";
 
+  private static final String AVG_BANDWIDTH_MASTER_PLAYLIST = " #EXTM3U \n"
+      + "\n"
+      + "#EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS=\"mp4a.40.2,avc1.66.30\",RESOLUTION=304x128\n"
+      + "http://example.com/low.m3u8\n"
+      + "\n"
+      + "#EXT-X-STREAM-INF:BANDWIDTH=1280000,AVERAGE-BANDWIDTH=1270000,"
+      + "CODECS=\"mp4a.40.2 , avc1.66.30 \"\n"
+      + "http://example.com/spaces_in_codecs.m3u8\n";
+
   private static final String PLAYLIST_WITH_INVALID_HEADER = "#EXTMU3\n"
       + "#EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS=\"mp4a.40.2,avc1.66.30\",RESOLUTION=304x128\n"
       + "http://example.com/low.m3u8\n";
@@ -70,42 +79,48 @@ public class HlsMasterPlaylistParserTest extends TestCase {
     HlsMasterPlaylist masterPlaylist = parseMasterPlaylist(PLAYLIST_URI, MASTER_PLAYLIST);
 
     List<HlsMasterPlaylist.HlsUrl> variants = masterPlaylist.variants;
-    assertNotNull(variants);
     assertEquals(5, variants.size());
     assertNull(masterPlaylist.muxedCaptionFormats);
 
     assertEquals(1280000, variants.get(0).format.bitrate);
-    assertNotNull(variants.get(0).format.codecs);
     assertEquals("mp4a.40.2,avc1.66.30", variants.get(0).format.codecs);
     assertEquals(304, variants.get(0).format.width);
     assertEquals(128, variants.get(0).format.height);
     assertEquals("http://example.com/low.m3u8", variants.get(0).url);
 
     assertEquals(1280000, variants.get(1).format.bitrate);
-    assertNotNull(variants.get(1).format.codecs);
     assertEquals("mp4a.40.2 , avc1.66.30 ", variants.get(1).format.codecs);
     assertEquals("http://example.com/spaces_in_codecs.m3u8", variants.get(1).url);
 
     assertEquals(2560000, variants.get(2).format.bitrate);
-    assertEquals(null, variants.get(2).format.codecs);
+    assertNull(variants.get(2).format.codecs);
     assertEquals(384, variants.get(2).format.width);
     assertEquals(160, variants.get(2).format.height);
     assertEquals("http://example.com/mid.m3u8", variants.get(2).url);
 
     assertEquals(7680000, variants.get(3).format.bitrate);
-    assertEquals(null, variants.get(3).format.codecs);
+    assertNull(variants.get(3).format.codecs);
     assertEquals(Format.NO_VALUE, variants.get(3).format.width);
     assertEquals(Format.NO_VALUE, variants.get(3).format.height);
     assertEquals("http://example.com/hi.m3u8", variants.get(3).url);
 
     assertEquals(65000, variants.get(4).format.bitrate);
-    assertNotNull(variants.get(4).format.codecs);
     assertEquals("mp4a.40.5", variants.get(4).format.codecs);
     assertEquals(Format.NO_VALUE, variants.get(4).format.width);
     assertEquals(Format.NO_VALUE, variants.get(4).format.height);
     assertEquals("http://example.com/audio-only.m3u8", variants.get(4).url);
   }
 
+  public void testMasterPlaylistWithBandwdithAverage() throws IOException {
+    HlsMasterPlaylist masterPlaylist = parseMasterPlaylist(PLAYLIST_URI,
+        AVG_BANDWIDTH_MASTER_PLAYLIST);
+
+    List<HlsMasterPlaylist.HlsUrl> variants = masterPlaylist.variants;
+
+    assertEquals(1280000, variants.get(0).format.bitrate);
+    assertEquals(1270000, variants.get(1).format.bitrate);
+  }
+
   public void testPlaylistWithInvalidHeader() throws IOException {
     try {
       parseMasterPlaylist(PLAYLIST_URI, PLAYLIST_WITH_INVALID_HEADER);

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistParser.java

@@ -75,7 +75,9 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
 
   private static final String ATTR_CLOSED_CAPTIONS_NONE = "CLOSED-CAPTIONS=NONE";
 
-  private static final Pattern REGEX_BANDWIDTH = Pattern.compile("BANDWIDTH=(\\d+)\\b");
+  private static final Pattern REGEX_AVERAGE_BANDWIDTH =
+      Pattern.compile("AVERAGE-BANDWIDTH=(\\d+)\\b");
+  private static final Pattern REGEX_BANDWIDTH = Pattern.compile("[^-]BANDWIDTH=(\\d+)\\b");
   private static final Pattern REGEX_CODECS = Pattern.compile("CODECS=\"(.+?)\"");
   private static final Pattern REGEX_RESOLUTION = Pattern.compile("RESOLUTION=(\\d+x\\d+)");
   private static final Pattern REGEX_TARGET_DURATION = Pattern.compile(TAG_TARGET_DURATION
@@ -235,6 +237,11 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
         }
       } else if (line.startsWith(TAG_STREAM_INF)) {
         int bitrate = parseIntAttr(line, REGEX_BANDWIDTH);
+        String averageBandwidthString = parseOptionalStringAttr(line, REGEX_AVERAGE_BANDWIDTH);
+        if (averageBandwidthString != null) {
+          // If available, the average bandwidth attribute is used as the variant's bitrate.
+          bitrate = Integer.parseInt(averageBandwidthString);
+        }
         String codecs = parseOptionalStringAttr(line, REGEX_CODECS);
         String resolutionString = parseOptionalStringAttr(line, REGEX_RESOLUTION);
         noClosedCaptions |= line.contains(ATTR_CLOSED_CAPTIONS_NONE);
@@ -406,14 +413,6 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
         initializationSegment, segments);
   }
 
-  private static String parseStringAttr(String line, Pattern pattern) throws ParserException {
-    Matcher matcher = pattern.matcher(line);
-    if (matcher.find() && matcher.groupCount() == 1) {
-      return matcher.group(1);
-    }
-    throw new ParserException("Couldn't match " + pattern.pattern() + " in " + line);
-  }
-
   private static int parseIntAttr(String line, Pattern pattern) throws ParserException {
     return Integer.parseInt(parseStringAttr(line, pattern));
   }
@@ -424,10 +423,15 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
 
   private static String parseOptionalStringAttr(String line, Pattern pattern) {
     Matcher matcher = pattern.matcher(line);
-    if (matcher.find()) {
+    return matcher.find() ? matcher.group(1) : null;
+  }
+
+  private static String parseStringAttr(String line, Pattern pattern) throws ParserException {
+    Matcher matcher = pattern.matcher(line);
+    if (matcher.find() && matcher.groupCount() == 1) {
       return matcher.group(1);
     }
-    return null;
+    throw new ParserException("Couldn't match " + pattern.pattern() + " in " + line);
   }
 
   private static boolean parseBooleanAttribute(String line, Pattern pattern, boolean defaultValue) {