Remove columnLock, columnCount (unimplemented) and rowLock (always true)

Also add a release note and simplify the test by removing the garbage
prefix and suffix.

RELEASENOTES.md

@@ -93,6 +93,10 @@
         that contained Binder objects` error when using
         `DefaultExtractorsFactory.setTextTrackTranscodingEnabled`
         ([#836](https://github.com/androidx/media/issues/836)).
+    *   CEA-708: Ignore `rowLock` value. The CEA-708-E S-2023 spec states that
+        `rowLock` and `columnLock` should both be assumed to be true, regardless
+        of the values present in the stream (`columnLock` support is not
+        implemented, so it's effectively assumed to always be false).
 *   Metadata:
     *   Fix bug where `MediaMetadata` was only populated from Vorbis comments
         with upper-case keys

libraries/extractor/src/main/java/androidx/media3/extractor/text/cea/Cea708Parser.java

@@ -784,11 +784,9 @@ public final class Cea708Parser implements SubtitleParser {
     captionChannelPacketData.skipBits(2); // null padding
     boolean visible = captionChannelPacketData.readBit();
 
-    // ANSI/CTA-708-E S-2023 spec (Section 8.4.7) indicates that rowLock and columnLock should be
+    // ANSI/CTA-708-E S-2023 spec (Section 8.4.7) indicates that rowLock and columnLock values in
-    // ignored and assumed to be lock
+    // the media should be ignored and assumed to be true.
     captionChannelPacketData.skipBits(2);
-    boolean rowLock = true;
-    boolean columnLock = true;
 
     int priority = captionChannelPacketData.readBits(3);
     // second byte
@@ -801,7 +799,8 @@ public final class Cea708Parser implements SubtitleParser {
     int rowCount = captionChannelPacketData.readBits(4);
     // fifth byte
     captionChannelPacketData.skipBits(2); // null padding
-    int columnCount = captionChannelPacketData.readBits(6);
+    // TODO: Add support for column count.
+    captionChannelPacketData.skipBits(6); // column count
     // sixth byte
     captionChannelPacketData.skipBits(2); // null padding
     int windowStyle = captionChannelPacketData.readBits(3);
@@ -809,14 +808,11 @@ public final class Cea708Parser implements SubtitleParser {
 
     cueInfoBuilder.defineWindow(
         visible,
-        rowLock,
-        columnLock,
         priority,
         relativePositioning,
         verticalAnchor,
         horizontalAnchor,
         rowCount,
-        columnCount,
         anchorId,
         windowStyle,
         penStyle);
@@ -977,7 +973,6 @@ public final class Cea708Parser implements SubtitleParser {
     private int horizontalAnchor;
     private int anchorId;
     private int rowCount;
-    private boolean rowLock;
     private int justification;
     private int windowStyleId;
     private int penStyleId;
@@ -1013,7 +1008,6 @@ public final class Cea708Parser implements SubtitleParser {
       horizontalAnchor = 0;
       anchorId = 0;
       rowCount = MAXIMUM_ROW_COUNT;
-      rowLock = true;
       justification = JUSTIFICATION_LEFT;
       windowStyleId = 0;
       penStyleId = 0;
@@ -1047,20 +1041,16 @@ public final class Cea708Parser implements SubtitleParser {
 
     public void defineWindow(
         boolean visible,
-        boolean rowLock,
-        boolean columnLock,
         int priority,
         boolean relativePositioning,
         int verticalAnchor,
         int horizontalAnchor,
         int rowCount,
-        int columnCount,
         int anchorId,
         int windowStyleId,
         int penStyleId) {
       this.defined = true;
       this.visible = visible;
-      this.rowLock = rowLock;
       this.priority = priority;
       this.relativePositioning = relativePositioning;
       this.verticalAnchor = verticalAnchor;
@@ -1072,14 +1062,12 @@ public final class Cea708Parser implements SubtitleParser {
         this.rowCount = rowCount + 1;
 
         // Trim any rolled up captions that are no longer valid, if applicable.
-        while ((rowLock && (rolledUpCaptions.size() >= this.rowCount))
+        while ((rolledUpCaptions.size() >= this.rowCount)
             || (rolledUpCaptions.size() >= MAXIMUM_ROW_COUNT)) {
           rolledUpCaptions.remove(0);
         }
       }
 
-      // TODO: Add support for column lock and count.
-
       if (windowStyleId != 0 && this.windowStyleId != windowStyleId) {
         this.windowStyleId = windowStyleId;
         // windowStyleId is 1-based.
@@ -1241,7 +1229,7 @@ public final class Cea708Parser implements SubtitleParser {
           backgroundColorStartPosition = 0;
         }
 
-        while ((rowLock && (rolledUpCaptions.size() >= rowCount))
+        while ((rolledUpCaptions.size() >= rowCount)
             || (rolledUpCaptions.size() >= MAXIMUM_ROW_COUNT)) {
           rolledUpCaptions.remove(0);
         }

libraries/extractor/src/test/java/androidx/media3/extractor/text/cea/Cea708ParserTest.java

@@ -139,20 +139,13 @@ public class Cea708ParserTest {
                     Bytes.concat(
                         windowDefinition,
                         setCurrentWindow,
-                        "row1\r\nrow2\r\nrow3\r\nrow4".getBytes(Charsets.US_ASCII)))));
+                        "row1\r\nrow2\r\nrow3\r\nrow4".getBytes(Charsets.UTF_8)))));
-    byte[] garbagePrefix = TestUtil.buildTestData(subtitleData.length * 2);
-    byte[] garbageSuffix = TestUtil.buildTestData(10);
-    byte[] subtitleDataWithGarbagePrefixAndSuffix =
-        Bytes.concat(garbagePrefix, subtitleData, garbageSuffix);
 
     List<CuesWithTiming> result = new ArrayList<>();
-    cea708Parser.parse(
+    cea708Parser.parse(subtitleData, SubtitleParser.OutputOptions.allCues(), result::add);
-        subtitleDataWithGarbagePrefixAndSuffix,
-        garbagePrefix.length,
-        subtitleData.length,
-        SubtitleParser.OutputOptions.allCues(),
-        result::add);
 
+    // Row count is 1 (which means 2 rows should be kept). Row lock is disabled in the media,
+    // but this is ignored and the result is still truncated to only the last two rows.
     assertThat(Iterables.getOnlyElement(Iterables.getOnlyElement(result).cues).text.toString())
         .isEqualTo("row3\nrow4");
   }