Merge pull request #7199 from TiVo:p-fix-stuckcaption

PiperOrigin-RevId: 308229206

RELEASENOTES.md

@@ -101,6 +101,9 @@
         used `start`, `middle` and `end`).
     *   Use anti-aliasing and bitmap filtering when displaying bitmap subtitles
         ([#6950](https://github.com/google/ExoPlayer/pull/6950)).
+    *   Implement timing-out of stuck CEA-608 captions (as permitted by
+        ANSI/CTA-608-E R-2014 Annex C.9) and set the default timeout to 16
+        seconds ([#7181](https://github.com/google/ExoPlayer/issues/7181)).
 *   DRM:
     *   Add support for attaching DRM sessions to clear content in the demo app.
     *   Remove `DrmSessionManager` references from all renderers.
@@ -111,8 +114,8 @@
         ([#7078](https://github.com/google/ExoPlayer/issues/7078)).
     *   Remove generics from DRM components.
 *   Downloads and caching:
-    *   Merge downloads in `SegmentDownloader` to improve overall download
-        speed ([#5978](https://github.com/google/ExoPlayer/issues/5978)).
+    *   Merge downloads in `SegmentDownloader` to improve overall download speed
+        ([#5978](https://github.com/google/ExoPlayer/issues/5978)).
     *   Replace `CacheDataSinkFactory` and `CacheDataSourceFactory` with
         `CacheDataSink.Factory` and `CacheDataSource.Factory` respectively.
     *   Remove `DownloadConstructorHelper` and use `CacheDataSource.Factory`

library/core/src/main/java/com/google/android/exoplayer2/text/SubtitleDecoderFactory.java

@@ -27,7 +27,6 @@ import com.google.android.exoplayer2.text.ttml.TtmlDecoder;
 import com.google.android.exoplayer2.text.tx3g.Tx3gDecoder;
 import com.google.android.exoplayer2.text.webvtt.Mp4WebvttDecoder;
 import com.google.android.exoplayer2.text.webvtt.WebvttDecoder;
-import com.google.android.exoplayer2.util.Clock;
 import com.google.android.exoplayer2.util.MimeTypes;
 
 /**
@@ -109,8 +108,10 @@ public interface SubtitleDecoderFactory {
                 return new Tx3gDecoder(format.initializationData);
               case MimeTypes.APPLICATION_CEA608:
               case MimeTypes.APPLICATION_MP4CEA608:
-                return new Cea608Decoder(mimeType, format.accessibilityChannel,
-                      16000L, Clock.DEFAULT);
+                return new Cea608Decoder(
+                    mimeType,
+                    format.accessibilityChannel,
+                    Cea608Decoder.MIN_DATA_CHANNEL_TIMEOUT_MS);
               case MimeTypes.APPLICATION_CEA708:
                 return new Cea708Decoder(format.accessibilityChannel, format.initializationData);
               case MimeTypes.APPLICATION_DVBSUBS:

library/core/src/main/java/com/google/android/exoplayer2/text/cea/Cea608Decoder.java

@@ -26,12 +26,14 @@ import android.text.style.StyleSpan;
 import android.text.style.UnderlineSpan;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.text.Cue;
 import com.google.android.exoplayer2.text.Subtitle;
 import com.google.android.exoplayer2.text.SubtitleDecoder;
+import com.google.android.exoplayer2.text.SubtitleDecoderException;
 import com.google.android.exoplayer2.text.SubtitleInputBuffer;
+import com.google.android.exoplayer2.text.SubtitleOutputBuffer;
 import com.google.android.exoplayer2.util.Assertions;
-import com.google.android.exoplayer2.util.Clock;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.ParsableByteArray;
@@ -41,11 +43,15 @@ import java.util.Collections;
 import java.util.List;
 import org.checkerframework.checker.nullness.compatqual.NullableType;
 
-/**
- * A {@link SubtitleDecoder} for CEA-608 (also known as "line 21 captions" and "EIA-608").
- */
+/** A {@link SubtitleDecoder} for CEA-608 (also known as "line 21 captions" and "EIA-608"). */
 public final class Cea608Decoder extends CeaDecoder {
 
+  /**
+   * The minimum value for the {@code validDataChannelTimeoutMs} constructor parameter permitted by
+   * ANSI/CTA-608-E R-2014 Annex C.9.
+   */
+  public static final long MIN_DATA_CHANNEL_TIMEOUT_MS = 16_000;
+
   private static final String TAG = "Cea608Decoder";
 
   private static final int CC_VALID_FLAG = 0x04;
@@ -238,6 +244,7 @@ public final class Cea608Decoder extends CeaDecoder {
   private final int packetLength;
   private final int selectedField;
   private final int selectedChannel;
+  private final long validDataChannelTimeoutUs;
   private final ArrayList<CueBuilder> cueBuilders;
 
   private CueBuilder currentCueBuilder;
@@ -258,26 +265,26 @@ public final class Cea608Decoder extends CeaDecoder {
   // service bytes and drops the rest.
   private boolean isInCaptionService;
 
-  // Static counter to keep track of last CC rendered. This is used to force erase the caption when
-  // the stream does not explicitly send control codes to remove caption as specified by
-  // CEA-608 Annex C.9
-  private long lastCueUpdateMs = C.TIME_UNSET;
-  private boolean captionEraseCommandSeen = false;
-  // CEA-608 Annex C.9 propose that if no data are received for the selected caption channel within
-  // a given time, the decoder should automatically erase the caption. The time limit should be no
-  // less than 16 seconds
+  private long lastCueUpdateUs;
 
-  // This value is set in the constructor. The automatic erasure is disabled when this value is 0
-  private long validDataChannelTimeoutMs = 0;
-  private Clock clock;
-
-  public Cea608Decoder(String mimeType, int accessibilityChannel, long timeoutMs, Clock clock) {
+  /**
+   * Constructs an instance.
+   *
+   * @param mimeType The MIME type of the CEA-608 data.
+   * @param accessibilityChannel The Accessibility channel, or {@link
+   *     com.google.android.exoplayer2.Format#NO_VALUE} if unknown.
+   * @param validDataChannelTimeoutMs The timeout (in milliseconds) permitted by ANSI/CTA-608-E
+   *     R-2014 Annex C.9 to clear "stuck" captions where no removal control code is received. The
+   *     timeout should be at least {@link #MIN_DATA_CHANNEL_TIMEOUT_MS} or {@link C#TIME_UNSET} for
+   *     no timeout.
+   */
+  public Cea608Decoder(String mimeType, int accessibilityChannel, long validDataChannelTimeoutMs) {
     ccData = new ParsableByteArray();
     cueBuilders = new ArrayList<>();
     currentCueBuilder = new CueBuilder(CC_MODE_UNKNOWN, DEFAULT_CAPTIONS_ROW_COUNT);
     currentChannel = NTSC_CC_CHANNEL_1;
-    validDataChannelTimeoutMs = timeoutMs;
-    this.clock = clock;
+    this.validDataChannelTimeoutUs =
+        validDataChannelTimeoutMs > 0 ? validDataChannelTimeoutMs * 1000 : C.TIME_UNSET;
     packetLength = MimeTypes.APPLICATION_MP4CEA608.equals(mimeType) ? 2 : 3;
     switch (accessibilityChannel) {
       case 1:
@@ -305,6 +312,7 @@ public final class Cea608Decoder extends CeaDecoder {
     setCaptionMode(CC_MODE_UNKNOWN);
     resetCueBuilders();
     isInCaptionService = true;
+    lastCueUpdateUs = C.TIME_UNSET;
   }
 
   @Override
@@ -326,7 +334,7 @@ public final class Cea608Decoder extends CeaDecoder {
     repeatableControlCc2 = 0;
     currentChannel = NTSC_CC_CHANNEL_1;
     isInCaptionService = true;
-    lastCueUpdateMs = C.TIME_UNSET;
+    lastCueUpdateUs = C.TIME_UNSET;
   }
 
   @Override
@@ -334,6 +342,26 @@ public final class Cea608Decoder extends CeaDecoder {
     // Do nothing
   }
 
+  @Nullable
+  @Override
+  public SubtitleOutputBuffer dequeueOutputBuffer() throws SubtitleDecoderException {
+    SubtitleOutputBuffer outputBuffer = super.dequeueOutputBuffer();
+    if (outputBuffer != null) {
+      return outputBuffer;
+    }
+    if (shouldClearStuckCaptions()) {
+      outputBuffer = getAvailableOutputBuffer();
+      if (outputBuffer != null) {
+        cues = Collections.emptyList();
+        lastCueUpdateUs = C.TIME_UNSET;
+        Subtitle subtitle = createSubtitle();
+        outputBuffer.setContent(getPositionUs(), subtitle, Format.OFFSET_SAMPLE_RELATIVE);
+        return outputBuffer;
+      }
+    }
+    return null;
+  }
+
   @Override
   protected boolean isNewSubtitleDataAvailable() {
     return cues != lastCues;
@@ -351,7 +379,6 @@ public final class Cea608Decoder extends CeaDecoder {
     ByteBuffer subtitleData = Assertions.checkNotNull(inputBuffer.data);
     ccData.reset(subtitleData.array(), subtitleData.limit());
     boolean captionDataProcessed = false;
-    captionEraseCommandSeen = false;
     while (ccData.bytesLeft() >= packetLength) {
       byte ccHeader = packetLength == 2 ? CC_IMPLICIT_DATA_HEADER
           : (byte) ccData.readUnsignedByte();
@@ -361,6 +388,7 @@ public final class Cea608Decoder extends CeaDecoder {
       // TODO: We're currently ignoring the top 5 marker bits, which should all be 1s according
       // to the CEA-608 specification. We need to determine if the data should be handled
       // differently when that is not the case.
+
       if ((ccHeader & CC_TYPE_FLAG) != 0) {
         // Do not process anything that is not part of the 608 byte stream.
         continue;
@@ -370,6 +398,7 @@ public final class Cea608Decoder extends CeaDecoder {
         // Do not process packets not within the selected field.
         continue;
       }
+
       // Strip the parity bit from each byte to get CC data.
       byte ccData1 = (byte) (ccByte1 & 0x7F);
       byte ccData2 = (byte) (ccByte2 & 0x7F);
@@ -439,9 +468,7 @@ public final class Cea608Decoder extends CeaDecoder {
     if (captionDataProcessed) {
       if (captionMode == CC_MODE_ROLL_UP || captionMode == CC_MODE_PAINT_ON) {
         cues = getDisplayCues();
-        if ((validDataChannelTimeoutMs != 0) && !captionEraseCommandSeen) {
-          lastCueUpdateMs = clock.elapsedRealtime();
-        }
+        lastCueUpdateUs = getPositionUs();
       }
     }
   }
@@ -560,17 +587,14 @@ public final class Cea608Decoder extends CeaDecoder {
         cues = Collections.emptyList();
         if (captionMode == CC_MODE_ROLL_UP || captionMode == CC_MODE_PAINT_ON) {
           resetCueBuilders();
-          captionEraseCommandSeen = true;
         }
         break;
       case CTRL_ERASE_NON_DISPLAYED_MEMORY:
         resetCueBuilders();
-        captionEraseCommandSeen = true;
         break;
       case CTRL_END_OF_CAPTION:
         cues = getDisplayCues();
         resetCueBuilders();
-        captionEraseCommandSeen = true;
         break;
       case CTRL_CARRIAGE_RETURN:
         // carriage returns only apply to rollup captions; don't bother if we don't have anything
@@ -1040,17 +1064,12 @@ public final class Cea608Decoder extends CeaDecoder {
 
   }
 
-  protected void clearStuckCaptions()
-  {
-      if ((validDataChannelTimeoutMs != 0) &&
-              (lastCueUpdateMs != C.TIME_UNSET)) {
-        long timeElapsed = clock.elapsedRealtime() - lastCueUpdateMs;
-        if (timeElapsed >= validDataChannelTimeoutMs) {
-          // Force erase captions. There might be stale captions stuck on screen.
-          // (CEA-608 Annex C.9)
-          cues = Collections.emptyList();
-          lastCueUpdateMs = C.TIME_UNSET;
-        }
-      }
+  /** See ANSI/CTA-608-E R-2014 Annex C.9 for Caption Erase Logic. */
+  private boolean shouldClearStuckCaptions() {
+    if (validDataChannelTimeoutUs == C.TIME_UNSET || lastCueUpdateUs == C.TIME_UNSET) {
+      return false;
+    }
+    long elapsedUs = getPositionUs() - lastCueUpdateUs;
+    return elapsedUs >= validDataChannelTimeoutUs;
   }
 }

library/core/src/main/java/com/google/android/exoplayer2/text/cea/Cea708Decoder.java

@@ -1296,14 +1296,6 @@ public final class Cea708Decoder extends CeaDecoder {
     }
   }
 
-  protected void clearStuckCaptions()
-  {
-    // Do nothing for CEA-708.
-    // As per spec CEA-708 Caption text sequences shall be terminated by either the start of a new
-    // DTVCC Command, or with an ASCII ETX (End of Text) (0x03) character when no other DTVCC
-    // Commands follow.
-  }
-
   /** A {@link Cue} for CEA-708. */
   private static final class Cea708CueInfo {
 

library/core/src/main/java/com/google/android/exoplayer2/text/cea/CeaDecoder.java

@@ -97,8 +97,6 @@ import java.util.PriorityQueue;
     if (availableOutputBuffers.isEmpty()) {
       return null;
     }
-    // check if 608 decoder needs to clean up the stale caption
-    clearStuckCaptions();
     // iterate through all available input buffers whose timestamps are less than or equal
     // to the current playback position; processing input buffers for future content should
     // be deferred until they would be applicable
@@ -181,6 +179,15 @@ import java.util.PriorityQueue;
    */
   protected abstract void decode(SubtitleInputBuffer inputBuffer);
 
+  @Nullable
+  protected final SubtitleOutputBuffer getAvailableOutputBuffer() {
+    return availableOutputBuffers.pollFirst();
+  }
+
+  protected final long getPositionUs() {
+    return playbackPositionUs;
+  }
+
   private static final class CeaInputBuffer extends SubtitleInputBuffer
       implements Comparable<CeaInputBuffer> {
 
@@ -215,9 +222,4 @@ import java.util.PriorityQueue;
       owner.releaseOutputBuffer(this);
     }
   }
-
-  /**
-   * Implements CEA-608 Annex C.9 automatic Caption Erase Logic
-   */
-  protected abstract void clearStuckCaptions();
 }