Further H264/H265 code deduping + fix NAL unescaping.

library/src/main/java/com/google/android/exoplayer/extractor/ts/H264Reader.java

@@ -66,7 +66,6 @@ import java.util.List;
 
   // Scratch variables to avoid allocations.
   private final ParsableByteArray seiWrapper;
-  private int[] scratchEscapePositions;
 
   public H264Reader(TrackOutput output, SeiReader seiReader, boolean idrKeyframesOnly) {
     super(output);
@@ -77,7 +76,6 @@ import java.util.List;
     pps = new NalUnitTargetBuffer(NAL_UNIT_TYPE_PPS, 128);
     sei = new NalUnitTargetBuffer(NAL_UNIT_TYPE_SEI, 128);
     seiWrapper = new ParsableByteArray();
-    scratchEscapePositions = new int[10];
   }
 
   @Override
@@ -191,7 +189,7 @@ import java.util.List;
     sps.endNalUnit(discardPadding);
     pps.endNalUnit(discardPadding);
     if (sei.endNalUnit(discardPadding)) {
-      int unescapedLength = unescapeStream(sei.nalData, sei.nalLength);
+      int unescapedLength = NalUnitUtil.unescapeStream(sei.nalData, sei.nalLength);
       seiWrapper.reset(sei.nalData, unescapedLength);
       seiWrapper.setPosition(4); // NAL prefix and nal_unit() header.
       seiReader.consume(seiWrapper, pesTimeUs, true);
@@ -208,7 +206,7 @@ import java.util.List;
     initializationData.add(ppsData);
 
     // Unescape and then parse the SPS unit.
-    unescapeStream(sps.nalData, sps.nalLength);
+    NalUnitUtil.unescapeStream(sps.nalData, sps.nalLength);
     ParsableBitArray bitArray = new ParsableBitArray(sps.nalData);
     bitArray.skipBits(32); // NAL header
     int profileIdc = bitArray.readBits(8);
@@ -322,57 +320,6 @@ import java.util.List;
     }
   }
 
-  /**
-   * Unescapes {@code data} up to the specified limit, replacing occurrences of [0, 0, 3] with
-   * [0, 0]. The unescaped data is returned in-place, with the return value indicating its length.
-   * <p>
-   * See ISO/IEC 14496-10:2005(E) page 36 for more information.
-   *
-   * @param data The data to unescape.
-   * @param limit The limit (exclusive) of the data to unescape.
-   * @return The length of the unescaped data.
-   */
-  private int unescapeStream(byte[] data, int limit) {
-    int position = 0;
-    int scratchEscapeCount = 0;
-    while (position < limit) {
-      position = findNextUnescapeIndex(data, position, limit);
-      if (position < limit) {
-        if (scratchEscapePositions.length <= scratchEscapeCount) {
-          // Grow scratchEscapePositions to hold a larger number of positions.
-          scratchEscapePositions = Arrays.copyOf(scratchEscapePositions,
-              scratchEscapePositions.length * 2);
-        }
-        scratchEscapePositions[scratchEscapeCount++] = position;
-        position += 3;
-      }
-    }
-
-    int unescapedLength = limit - scratchEscapeCount;
-    int escapedPosition = 0; // The position being read from.
-    int unescapedPosition = 0; // The position being written to.
-    for (int i = 0; i < scratchEscapeCount; i++) {
-      int nextEscapePosition = scratchEscapePositions[i];
-      int copyLength = nextEscapePosition - escapedPosition;
-      System.arraycopy(data, escapedPosition, data, unescapedPosition, copyLength);
-      escapedPosition += copyLength + 3;
-      unescapedPosition += copyLength + 2;
-    }
-
-    int remainingLength = unescapedLength - unescapedPosition;
-    System.arraycopy(data, escapedPosition, data, unescapedPosition, remainingLength);
-    return unescapedLength;
-  }
-
-  private static int findNextUnescapeIndex(byte[] bytes, int offset, int limit) {
-    for (int i = offset; i < limit - 2; i++) {
-      if (bytes[i] == 0x00 && bytes[i + 1] == 0x00 && bytes[i + 2] == 0x03) {
-        return i;
-      }
-    }
-    return limit;
-  }
-
   /**
    * A buffer specifically for IFR units that can be used to parse the IFR's slice type.
    */

library/src/main/java/com/google/android/exoplayer/extractor/ts/H265Reader.java

@@ -25,7 +25,6 @@ import com.google.android.exoplayer.util.ParsableByteArray;
 
 import android.util.Log;
 
-import java.util.Arrays;
 import java.util.Collections;
 
 /**
@@ -71,7 +70,6 @@ import java.util.Collections;
 
   // Scratch variables to avoid allocations.
   private final ParsableByteArray seiWrapper;
-  private int[] scratchEscapePositions;
 
   public H265Reader(TrackOutput output, SeiReader seiReader) {
     super(output);
@@ -83,7 +81,6 @@ import java.util.Collections;
     prefixSei = new NalUnitTargetBuffer(PREFIX_SEI_NUT, 128);
     suffixSei = new NalUnitTargetBuffer(SUFFIX_SEI_NUT, 128);
     seiWrapper = new ParsableByteArray();
-    scratchEscapePositions = new int[10];
   }
 
   @Override
@@ -189,7 +186,7 @@ import java.util.Collections;
     sps.endNalUnit(discardPadding);
     pps.endNalUnit(discardPadding);
     if (prefixSei.endNalUnit(discardPadding)) {
-      int unescapedLength = unescapeStream(prefixSei.nalData, prefixSei.nalLength);
+      int unescapedLength = NalUnitUtil.unescapeStream(prefixSei.nalData, prefixSei.nalLength);
       seiWrapper.reset(prefixSei.nalData, unescapedLength);
 
       // Skip the NAL prefix and type.
@@ -197,7 +194,7 @@ import java.util.Collections;
       seiReader.consume(seiWrapper, pesTimeUs, true);
     }
     if (suffixSei.endNalUnit(discardPadding)) {
-      int unescapedLength = unescapeStream(suffixSei.nalData, suffixSei.nalLength);
+      int unescapedLength = NalUnitUtil.unescapeStream(suffixSei.nalData, suffixSei.nalLength);
       seiWrapper.reset(suffixSei.nalData, unescapedLength);
 
       // Skip the NAL prefix and type.
@@ -215,7 +212,7 @@ import java.util.Collections;
     System.arraycopy(pps.nalData, 0, csd, vps.nalLength + sps.nalLength, pps.nalLength);
 
     // Unescape and then parse the SPS NAL unit, as per H.265/HEVC (2014) 7.3.2.2.1.
-    unescapeStream(sps.nalData, sps.nalLength);
+    NalUnitUtil.unescapeStream(sps.nalData, sps.nalLength);
     ParsableBitArray bitArray = new ParsableBitArray(sps.nalData);
     bitArray.skipBits(40 + 4); // NAL header, sps_video_parameter_set_id
     int maxSubLayersMinus1 = bitArray.readBits(3);
@@ -339,56 +336,6 @@ import java.util.Collections;
     }
   }
 
-  // TODO: Deduplicate with H264Reader.
-  /**
-   * Unescapes {@code data} up to the specified limit, replacing occurrences of [0, 0, 3] with
-   * [0, 0]. The unescaped data is returned in-place, with the return value indicating its length.
-   *
-   * @param data The data to unescape.
-   * @param limit The limit (exclusive) of the data to unescape.
-   * @return The length of the unescaped data.
-   */
-  private int unescapeStream(byte[] data, int limit) {
-    int position = 0;
-    int scratchEscapeCount = 0;
-    while (position < limit) {
-      position = findNextUnescapeIndex(data, position, limit);
-      if (position < limit) {
-        if (scratchEscapePositions.length <= scratchEscapeCount) {
-          // Grow scratchEscapePositions to hold a larger number of positions.
-          scratchEscapePositions = Arrays.copyOf(scratchEscapePositions,
-              scratchEscapePositions.length * 2);
-        }
-        scratchEscapePositions[scratchEscapeCount++] = position;
-        position += 3;
-      }
-    }
-
-    int unescapedLength = limit - scratchEscapeCount;
-    int escapedPosition = 0; // The position being read from.
-    int unescapedPosition = 0; // The position being written to.
-    for (int i = 0; i < scratchEscapeCount; i++) {
-      int nextEscapePosition = scratchEscapePositions[i];
-      int copyLength = nextEscapePosition - escapedPosition;
-      System.arraycopy(data, escapedPosition, data, unescapedPosition, copyLength);
-      escapedPosition += copyLength + 3;
-      unescapedPosition += copyLength + 2;
-    }
-
-    int remainingLength = unescapedLength - unescapedPosition;
-    System.arraycopy(data, escapedPosition, data, unescapedPosition, remainingLength);
-    return unescapedLength;
-  }
-
-  private static int findNextUnescapeIndex(byte[] bytes, int offset, int limit) {
-    for (int i = offset; i < limit - 2; i++) {
-      if (bytes[i] == 0x00 && bytes[i + 1] == 0x00 && bytes[i + 2] == 0x03) {
-        return i;
-      }
-    }
-    return limit;
-  }
-
   /** Returns whether the NAL unit is a random access point. */
   private static boolean isRandomAccessPoint(int nalUnitType) {
     return nalUnitType == BLA_W_LP || nalUnitType == BLA_W_RADL || nalUnitType == BLA_N_LP

library/src/main/java/com/google/android/exoplayer/util/NalUnitUtil.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer.util;
 
 import java.nio.ByteBuffer;
+import java.util.Arrays;
 
 /**
  * Utility methods for handling H.264/AVC and H.265/HEVC NAL units.
@@ -48,6 +49,61 @@ public final class NalUnitUtil {
     2f
   };
 
+  private static final Object scratchEscapePositionsLock = new Object();
+
+  /**
+   * Temporary store for positions of escape codes in {@link #unescapeStream(byte[], int)}. Guarded
+   * by {@link #scratchEscapePositionsLock}.
+   */
+  private static int[] scratchEscapePositions = new int[10];
+
+  /**
+   * Unescapes {@code data} up to the specified limit, replacing occurrences of [0, 0, 3] with
+   * [0, 0]. The unescaped data is returned in-place, with the return value indicating its length.
+   * <p>
+   * Executions of this method are mutually exclusive, so it should not be called with very large
+   * buffers.
+   *
+   * @param data The data to unescape.
+   * @param limit The limit (exclusive) of the data to unescape.
+   * @return The length of the unescaped data.
+   */
+  public static int unescapeStream(byte[] data, int limit) {
+    synchronized (scratchEscapePositionsLock) {
+      int position = 0;
+      int scratchEscapeCount = 0;
+      while (position < limit) {
+        position = findNextUnescapeIndex(data, position, limit);
+        if (position < limit) {
+          if (scratchEscapePositions.length <= scratchEscapeCount) {
+            // Grow scratchEscapePositions to hold a larger number of positions.
+            scratchEscapePositions = Arrays.copyOf(scratchEscapePositions,
+                scratchEscapePositions.length * 2);
+          }
+          scratchEscapePositions[scratchEscapeCount++] = position;
+          position += 3;
+        }
+      }
+
+      int unescapedLength = limit - scratchEscapeCount;
+      int escapedPosition = 0; // The position being read from.
+      int unescapedPosition = 0; // The position being written to.
+      for (int i = 0; i < scratchEscapeCount; i++) {
+        int nextEscapePosition = scratchEscapePositions[i];
+        int copyLength = nextEscapePosition - escapedPosition;
+        System.arraycopy(data, escapedPosition, data, unescapedPosition, copyLength);
+        unescapedPosition += copyLength;
+        data[unescapedPosition++] = 0;
+        data[unescapedPosition++] = 0;
+        escapedPosition += copyLength + 3;
+      }
+
+      int remainingLength = unescapedLength - unescapedPosition;
+      System.arraycopy(data, escapedPosition, data, unescapedPosition, remainingLength);
+      return unescapedLength;
+    }
+  }
+
   /**
    * Replaces length prefixes of NAL units in {@code buffer} with start code prefixes, within the
    * {@code size} bytes preceding the buffer's position.
@@ -189,6 +245,15 @@ public final class NalUnitUtil {
     prefixFlags[2] = false;
   }
 
+  private static int findNextUnescapeIndex(byte[] bytes, int offset, int limit) {
+    for (int i = offset; i < limit - 2; i++) {
+      if (bytes[i] == 0x00 && bytes[i + 1] == 0x00 && bytes[i + 2] == 0x03) {
+        return i;
+      }
+    }
+    return limit;
+  }
+
   /**
    * Reads an unsigned integer into an integer. This method is suitable for use when it can be
    * assumed that the top bit will always be set to zero.

library/src/test/java/com/google/android/exoplayer/util/NalUnitUtilTest.java

@@ -110,6 +110,18 @@ public class NalUnitUtilTest extends TestCase {
     assertPrefixFlagsCleared(prefixFlags);
   }
 
+  public void testUnescapeDoesNotModifyBuffersWithoutStartCodes() {
+    assertUnescapeDoesNotModify("");
+    assertUnescapeDoesNotModify("0000");
+    assertUnescapeDoesNotModify("172BF38A3C");
+    assertUnescapeDoesNotModify("000004");
+  }
+
+  public void testUnescapeModifiesBuffersWithStartCodes() {
+    assertUnescapeMatchesExpected("00000301", "000001");
+    assertUnescapeMatchesExpected("0000030200000300", "000002000000");
+  }
+
   private static byte[] buildTestData() {
     byte[] data = new byte[20];
     for (int i = 0; i < data.length; i++) {
@@ -130,4 +142,29 @@ public class NalUnitUtilTest extends TestCase {
     assertEquals(false, flags[0] || flags[1] || flags[2]);
   }
 
+  private static void assertUnescapeDoesNotModify(String input) {
+    assertUnescapeMatchesExpected(input, input);
+  }
+
+  private static void assertUnescapeMatchesExpected(String input, String expectedOutput) {
+    byte[] bitstream = getByteArrayForHexString(input);
+    byte[] expectedOutputBitstream = getByteArrayForHexString(expectedOutput);
+    int count = NalUnitUtil.unescapeStream(bitstream, bitstream.length);
+    assertEquals(expectedOutputBitstream.length, count);
+    byte[] outputBitstream = new byte[count];
+    System.arraycopy(bitstream, 0, outputBitstream, 0, count);
+    assertTrue(Arrays.equals(expectedOutputBitstream, outputBitstream));
+  }
+
+  private static byte[] getByteArrayForHexString(String hexString) {
+    int length = hexString.length();
+    Assertions.checkArgument(length % 2 == 0);
+    byte[] result = new byte[length / 2];
+    for (int i = 0; i < result.length; i++) {
+      result[i] = (byte) ((Character.digit(hexString.charAt(i * 2), 16) << 4)
+          + Character.digit(hexString.charAt(i * 2 + 1), 16));
+    }
+    return result;
+  }
+
 }