1 files changed, 259 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/ts/PsDurationReader.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/ts/PsDurationReader.java
new file mode 100644
index 0000000000..a5960fbe15
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/ts/PsDurationReader.java
@@ -0,0 +1,259 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ts;
+
+import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.Extractor;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorInput;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.PositionHolder;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.TimestampAdjuster;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Util;
+import java.io.IOException;
+
+/**
+ * A reader that can extract the approximate duration from a given MPEG program stream (PS).
+ *
+ * <p>This reader extracts the duration by reading system clock reference (SCR) values from the
+ * header of a pack at the start and at the end of the stream, calculating the difference, and
+ * converting that into stream duration. This reader also handles the case when a single SCR
+ * wraparound takes place within the stream, which can make SCR values at the beginning of the
+ * stream larger than SCR values at the end. This class can only be used once to read duration from
+ * a given stream, and the usage of the class is not thread-safe, so all calls should be made from
+ * the same thread.
+ *
+ * <p>Note: See ISO/IEC 13818-1, Table 2-33 for details of the SCR field in pack_header.
+ */
+/* package */ final class PsDurationReader {
+
+  private static final int TIMESTAMP_SEARCH_BYTES = 20000;
+
+  private final TimestampAdjuster scrTimestampAdjuster;
+  private final ParsableByteArray packetBuffer;
+
+  private boolean isDurationRead;
+  private boolean isFirstScrValueRead;
+  private boolean isLastScrValueRead;
+
+  private long firstScrValue;
+  private long lastScrValue;
+  private long durationUs;
+
+  /* package */ PsDurationReader() {
+    scrTimestampAdjuster = new TimestampAdjuster(/* firstSampleTimestampUs= */ 0);
+    firstScrValue = C.TIME_UNSET;
+    lastScrValue = C.TIME_UNSET;
+    durationUs = C.TIME_UNSET;
+    packetBuffer = new ParsableByteArray();
+  }
+
+  /** Returns true if a PS duration has been read. */
+  public boolean isDurationReadFinished() {
+    return isDurationRead;
+  }
+
+  public TimestampAdjuster getScrTimestampAdjuster() {
+    return scrTimestampAdjuster;
+  }
+
+  /**
+   * Reads a PS duration from the input.
+   *
+   * <p>This reader reads the duration by reading SCR values from the header of a pack at the start
+   * and at the end of the stream, calculating the difference, and converting that into stream
+   * duration.
+   *
+   * @param input The {@link ExtractorInput} from which data should be read.
+   * @param seekPositionHolder If {@link Extractor#RESULT_SEEK} is returned, this holder is updated
+   *     to hold the position of the required seek.
+   * @return One of the {@code RESULT_} values defined in {@link Extractor}.
+   * @throws IOException If an error occurred reading from the input.
+   * @throws InterruptedException If the thread was interrupted.
+   */
+  public @Extractor.ReadResult int readDuration(
+      ExtractorInput input, PositionHolder seekPositionHolder)
+      throws IOException, InterruptedException {
+    if (!isLastScrValueRead) {
+      return readLastScrValue(input, seekPositionHolder);
+    }
+    if (lastScrValue == C.TIME_UNSET) {
+      return finishReadDuration(input);
+    }
+    if (!isFirstScrValueRead) {
+      return readFirstScrValue(input, seekPositionHolder);
+    }
+    if (firstScrValue == C.TIME_UNSET) {
+      return finishReadDuration(input);
+    }
+
+    long minScrPositionUs = scrTimestampAdjuster.adjustTsTimestamp(firstScrValue);
+    long maxScrPositionUs = scrTimestampAdjuster.adjustTsTimestamp(lastScrValue);
+    durationUs = maxScrPositionUs - minScrPositionUs;
+    return finishReadDuration(input);
+  }
+
+  /** Returns the duration last read from {@link #readDuration(ExtractorInput, PositionHolder)}. */
+  public long getDurationUs() {
+    return durationUs;
+  }
+
+  /**
+   * Returns the SCR value read from the next pack in the stream, given the buffer at the pack
+   * header start position (just behind the pack start code).
+   */
+  public static long readScrValueFromPack(ParsableByteArray packetBuffer) {
+    int originalPosition = packetBuffer.getPosition();
+    if (packetBuffer.bytesLeft() < 9) {
+      // We require at 9 bytes for pack header to read scr value
+      return C.TIME_UNSET;
+    }
+    byte[] scrBytes = new byte[9];
+    packetBuffer.readBytes(scrBytes, /* offset= */ 0, scrBytes.length);
+    packetBuffer.setPosition(originalPosition);
+    if (!checkMarkerBits(scrBytes)) {
+      return C.TIME_UNSET;
+    }
+    return readScrValueFromPackHeader(scrBytes);
+  }
+
+  private int finishReadDuration(ExtractorInput input) {
+    packetBuffer.reset(Util.EMPTY_BYTE_ARRAY);
+    isDurationRead = true;
+    input.resetPeekPosition();
+    return Extractor.RESULT_CONTINUE;
+  }
+
+  private int readFirstScrValue(ExtractorInput input, PositionHolder seekPositionHolder)
+      throws IOException, InterruptedException {
+    int bytesToSearch = (int) Math.min(TIMESTAMP_SEARCH_BYTES, input.getLength());
+    int searchStartPosition = 0;
+    if (input.getPosition() != searchStartPosition) {
+      seekPositionHolder.position = searchStartPosition;
+      return Extractor.RESULT_SEEK;
+    }
+
+    packetBuffer.reset(bytesToSearch);
+    input.resetPeekPosition();
+    input.peekFully(packetBuffer.data, /* offset= */ 0, bytesToSearch);
+
+    firstScrValue = readFirstScrValueFromBuffer(packetBuffer);
+    isFirstScrValueRead = true;
+    return Extractor.RESULT_CONTINUE;
+  }
+
+  private long readFirstScrValueFromBuffer(ParsableByteArray packetBuffer) {
+    int searchStartPosition = packetBuffer.getPosition();
+    int searchEndPosition = packetBuffer.limit();
+    for (int searchPosition = searchStartPosition;
+        searchPosition < searchEndPosition - 3;
+        searchPosition++) {
+      int nextStartCode = peekIntAtPosition(packetBuffer.data, searchPosition);
+      if (nextStartCode == PsExtractor.PACK_START_CODE) {
+        packetBuffer.setPosition(searchPosition + 4);
+        long scrValue = readScrValueFromPack(packetBuffer);
+        if (scrValue != C.TIME_UNSET) {
+          return scrValue;
+        }
+      }
+    }
+    return C.TIME_UNSET;
+  }
+
+  private int readLastScrValue(ExtractorInput input, PositionHolder seekPositionHolder)
+      throws IOException, InterruptedException {
+    long inputLength = input.getLength();
+    int bytesToSearch = (int) Math.min(TIMESTAMP_SEARCH_BYTES, inputLength);
+    long searchStartPosition = inputLength - bytesToSearch;
+    if (input.getPosition() != searchStartPosition) {
+      seekPositionHolder.position = searchStartPosition;
+      return Extractor.RESULT_SEEK;
+    }
+
+    packetBuffer.reset(bytesToSearch);
+    input.resetPeekPosition();
+    input.peekFully(packetBuffer.data, /* offset= */ 0, bytesToSearch);
+
+    lastScrValue = readLastScrValueFromBuffer(packetBuffer);
+    isLastScrValueRead = true;
+    return Extractor.RESULT_CONTINUE;
+  }
+
+  private long readLastScrValueFromBuffer(ParsableByteArray packetBuffer) {
+    int searchStartPosition = packetBuffer.getPosition();
+    int searchEndPosition = packetBuffer.limit();
+    for (int searchPosition = searchEndPosition - 4;
+        searchPosition >= searchStartPosition;
+        searchPosition--) {
+      int nextStartCode = peekIntAtPosition(packetBuffer.data, searchPosition);
+      if (nextStartCode == PsExtractor.PACK_START_CODE) {
+        packetBuffer.setPosition(searchPosition + 4);
+        long scrValue = readScrValueFromPack(packetBuffer);
+        if (scrValue != C.TIME_UNSET) {
+          return scrValue;
+        }
+      }
+    }
+    return C.TIME_UNSET;
+  }
+
+  private int peekIntAtPosition(byte[] data, int position) {
+    return (data[position] & 0xFF) << 24
+        | (data[position + 1] & 0xFF) << 16
+        | (data[position + 2] & 0xFF) << 8
+        | (data[position + 3] & 0xFF);
+  }
+
+  private static boolean checkMarkerBits(byte[] scrBytes) {
+    // Verify the 01xxx1xx marker on the 0th byte
+    if ((scrBytes[0] & 0xC4) != 0x44) {
+      return false;
+    }
+    // 1st byte belongs to scr field.
+    // Verify the xxxxx1xx marker on the 2nd byte
+    if ((scrBytes[2] & 0x04) != 0x04) {
+      return false;
+    }
+    // 3rd byte belongs to scr field.
+    // Verify the xxxxx1xx marker on the 4rd byte
+    if ((scrBytes[4] & 0x04) != 0x04) {
+      return false;
+    }
+    // Verify the xxxxxxx1 marker on the 5th byte
+    if ((scrBytes[5] & 0x01) != 0x01) {
+      return false;
+    }
+    // 6th and 7th bytes belongs to program_max_rate field.
+    // Verify the xxxxxx11 marker on the 8th byte
+    return (scrBytes[8] & 0x03) == 0x03;
+  }
+
+  /**
+   * Returns the value of SCR base - 33 bits in big endian order from the PS pack header, ignoring
+   * the marker bits. Note: See ISO/IEC 13818-1, Table 2-33 for details of the SCR field in
+   * pack_header.
+   *
+   * <p>We ignore SCR Ext, because it's too small to have any significance.
+   */
+  private static long readScrValueFromPackHeader(byte[] scrBytes) {
+    return ((scrBytes[0] & 0b00111000L) >> 3) << 30
+        | (scrBytes[0] & 0b00000011L) << 28
+        | (scrBytes[1] & 0xFFL) << 20
+        | ((scrBytes[2] & 0b11111000L) >> 3) << 15
+        | (scrBytes[2] & 0b00000011L) << 13
+        | (scrBytes[3] & 0xFFL) << 5
+        | (scrBytes[4] & 0b11111000L) >> 3;
+  }
+}