webm_extractor: Add support for parsing BlockGroup element

This CL adds support for parsing BlockGroup elements for all
codecs (not just opus). It also adds a test to verify the new
behavior.

library/src/main/java/com/google/android/exoplayer/extractor/webm/WebmExtractor.java

@@ -82,6 +82,7 @@ public final class WebmExtractor implements Extractor {
   private static final int ID_SIMPLE_BLOCK = 0xA3;
   private static final int ID_BLOCK_GROUP = 0xA0;
   private static final int ID_BLOCK = 0xA1;
+  private static final int ID_REFERENCE_BLOCK = 0xFB;
   private static final int ID_TRACKS = 0x1654AE6B;
   private static final int ID_TRACK_ENTRY = 0xAE;
   private static final int ID_TRACK_NUMBER = 0xD7;
@@ -152,6 +153,7 @@ public final class WebmExtractor implements Extractor {
   private int sampleFlags;
   private long sampleTimeUs;
   private boolean sampleRead;
+  private boolean sampleSeenReferenceBlock;
 
   // Extractor outputs.
   private ExtractorOutput extractorOutput;
@@ -236,6 +238,7 @@ public final class WebmExtractor implements Extractor {
       case ID_CONTENT_ENCRYPTION_AES_SETTINGS_CIPHER_MODE:
       case ID_CUE_TIME:
       case ID_CUE_CLUSTER_POSITION:
+      case ID_REFERENCE_BLOCK:
         return EbmlReader.TYPE_UNSIGNED_INT;
       case ID_DOC_TYPE:
       case ID_CODEC_ID:
@@ -282,6 +285,9 @@ public final class WebmExtractor implements Extractor {
           seekForCues = true;
         }
         return;
+      case ID_BLOCK_GROUP:
+        sampleSeenReferenceBlock = false;
+        return;
       case ID_CONTENT_ENCODING:
         // TODO: check and fail if more than one content encoding is present.
         return;
@@ -314,6 +320,19 @@ public final class WebmExtractor implements Extractor {
           // We have already built the cues. Ignore.
         }
         return;
+      case ID_BLOCK_GROUP:
+        if (sampleState != SAMPLE_STATE_DATA) {
+          // We've skipped this sample (due to incompatible track number).
+          return;
+        }
+        // If the ReferenceBlock element was not found for this sample, then it is a keyframe.
+        if (!sampleSeenReferenceBlock) {
+          sampleFlags |= C.SAMPLE_FLAG_SYNC;
+        }
+        outputSampleMetadata(
+            (audioTrackFormat != null && sampleTrackNumber == audioTrackFormat.number)
+                ? audioTrackFormat.trackOutput : videoTrackFormat.trackOutput);
+        return;
       case ID_CONTENT_ENCODING:
         if (!trackFormat.hasContentEncryption) {
           // We found a ContentEncoding other than Encryption.
@@ -405,6 +424,9 @@ public final class WebmExtractor implements Extractor {
       case ID_CHANNELS:
         trackFormat.channelCount = (int) value;
         return;
+      case ID_REFERENCE_BLOCK:
+        sampleSeenReferenceBlock = true;
+        return;
       case ID_CONTENT_ENCODING_ORDER:
         // This extractor only supports one ContentEncoding element and hence the order has to be 0.
         if (value != 0) {
@@ -551,16 +573,8 @@ public final class WebmExtractor implements Extractor {
             throw new ParserException("Lacing mode not supported: " + lacing);
           }
           boolean isInvisible = (sampleHeaderScratchData[2] & 0x08) == 0x08;
-          boolean isKeyframe;
+          boolean isKeyframe =
-          if (id == ID_BLOCK) {
+              (id == ID_SIMPLE_BLOCK && (sampleHeaderScratchData[2] & 0x80) == 0x80);
-            // Matroska Block element does not self-sufficiently say whether it is a keyframe. It
-            // depends on the existence of another element (ReferenceBlock) which may occur after
-            // the Block element. Since this extractor uses Block element only for Opus, we set the
-            // keyframe to be true always since all Opus frames are key frames.
-            isKeyframe = true;
-          } else {
-            isKeyframe = (sampleHeaderScratchData[2] & 0x80) == 0x80;
-          }
           boolean isEncrypted = false;
 
           // If encrypted, the fourth byte is an encryption signal byte.
@@ -601,15 +615,24 @@ public final class WebmExtractor implements Extractor {
           sampleSize += 4;
         }
 
-        trackOutput.sampleMetadata(sampleTimeUs, sampleFlags, sampleSize, 0, null);
+        // For SimpleBlock, we send the metadata here as we have all the information. For Block, we
-        sampleState = SAMPLE_STATE_START;
+        // send the metadata at the end of the BlockGroup element since we'll know if the frame is a
-        sampleRead = true;
+        // keyframe or not only at that point.
+        if (id == ID_SIMPLE_BLOCK) {
+          outputSampleMetadata(trackOutput);
+        }
         return;
       default:
         throw new IllegalStateException("Unexpected id: " + id);
     }
   }
 
+  private void outputSampleMetadata(TrackOutput trackOutput) {
+    trackOutput.sampleMetadata(sampleTimeUs, sampleFlags, sampleSize, 0, null);
+    sampleState = SAMPLE_STATE_START;
+    sampleRead = true;
+  }
+
   /**
    * Builds an video {@link MediaFormat} containing recently gathered Video information.
    *

library/src/test/java/com/google/android/exoplayer/extractor/webm/WebmExtractorTest.java

@@ -334,6 +334,19 @@ public class WebmExtractorTest extends InstrumentationTestCase {
     assertSample(mediaSegment, 0, true, false, false, audioOutput);
   }
 
+  public void testReadBlockNonKeyframe() throws IOException, InterruptedException {
+    MediaSegment mediaSegment =
+        createMediaSegment(100, 0, 0, false, false, false, false, false, 1);
+    byte[] testInputData = joinByteArrays(
+        createInitializationSegment(
+            1, mediaSegment.clusterBytes.length, true, DEFAULT_TIMECODE_SCALE,
+            new int[] { ID_VP9 }, null),
+        mediaSegment.clusterBytes);
+    consume(testInputData);
+    assertVideoFormat();
+    assertSample(mediaSegment, 0, false, false, false, videoOutput);
+  }
+
   public void testReadEncryptedFrame() throws IOException, InterruptedException {
     MediaSegment mediaSegment = createMediaSegment(100, 0, 0, true, false, true, true, true, 1);
     ContentEncodingSettings settings = new ContentEncodingSettings(0, 1, 1, 5, 1);
@@ -466,7 +479,6 @@ public class WebmExtractorTest extends InstrumentationTestCase {
     assertEquals(keyframe, (output.sampleFlags & C.SAMPLE_FLAG_SYNC) != 0);
     assertEquals(invisible, (output.sampleFlags & C.SAMPLE_FLAG_DECODE_ONLY) != 0);
     assertEquals(encrypted, (output.sampleFlags & C.SAMPLE_FLAG_ENCRYPTED) != 0);
-
   }
 
   private byte[] createInitializationSegment(int cuePoints, int mediaSegmentSize,
@@ -522,7 +534,8 @@ public class WebmExtractorTest extends InstrumentationTestCase {
       blockBytes = createSimpleBlockElement(data.length, blockTimecode,
           keyframe, invisible, true, encrypted, validSignalByte, trackNumber);
     } else {
-      blockBytes = createBlockElement(data.length, blockTimecode, invisible, true, trackNumber);
+      blockBytes = createBlockElement(data.length, blockTimecode,
+          keyframe, invisible, true, trackNumber);
     }
     byte[] clusterBytes =
         createClusterElement(blockBytes.length + data.length, clusterTimecode);
@@ -762,22 +775,29 @@ public class WebmExtractorTest extends InstrumentationTestCase {
   }
 
   private static byte[] createBlockElement(
-      int size, int timecode, boolean invisible, boolean noLacing, int trackNumber) {
+      int size, int timecode, boolean keyframe, boolean invisible, boolean noLacing,
+      int trackNumber) {
     int blockSize = size + 5;
     byte[] blockSizeBytes = getIntegerBytes(blockSize);
     byte[] timeBytes = getIntegerBytes(timecode);
     byte[] trackNumberBytes = getIntegerBytes(trackNumber);
-    int blockElementSize = 1 + 8 + blockSize; // id + size + length of data
+    // Size of blockgroup = id + size + size of reference block + length of data.
-    byte[] sizeBytes = getIntegerBytes(blockElementSize);
+    int blockGroupElementSize = 1 + 8 + (keyframe ? 0 : 3) +  blockSize;
+    byte[] sizeBytes = getIntegerBytes(blockGroupElementSize);
     byte flags = (byte) ((invisible ? 0x08 : 0x00) | (noLacing ? 0x00 : 0x06));
-    return createByteArray(
+    byte[] blockGroupHeader = createByteArray(
         0xA0, // BlockGroup
-        0x01, 0x00, 0x00, 0x00, sizeBytes[0], sizeBytes[1], sizeBytes[2], sizeBytes[3],
+        0x01, 0x00, 0x00, 0x00, sizeBytes[0], sizeBytes[1], sizeBytes[2], sizeBytes[3]);
+    byte[] referenceBlock = keyframe ? new byte[0] : createByteArray(
+        0xFB, // ReferenceBlock
+        0x81, 0x00); // size=1 value=0
+    byte[] blockData = createByteArray(
         0xA1, // Block
         0x01, 0x00, 0x00, 0x00,
         blockSizeBytes[0], blockSizeBytes[1], blockSizeBytes[2], blockSizeBytes[3],
         0x40, trackNumberBytes[3], // Track number size=2
         timeBytes[2], timeBytes[3], flags); // Timecode and flags
+    return joinByteArrays(blockGroupHeader, referenceBlock, blockData);
   }
 
   private static byte[] createFrameData(int size) {