1 files changed, 178 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/audio/TrimmingAudioProcessor.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/audio/TrimmingAudioProcessor.java
new file mode 100644
index 0000000000..1326cf63ee
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/audio/TrimmingAudioProcessor.java
@@ -0,0 +1,178 @@
+/*
+ * Copyright (C) 2017 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.audio;
+
+import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Util;
+import java.nio.ByteBuffer;
+
+/** Audio processor for trimming samples from the start/end of data. */
+/* package */ final class TrimmingAudioProcessor extends BaseAudioProcessor {
+
+  @C.PcmEncoding private static final int OUTPUT_ENCODING = C.ENCODING_PCM_16BIT;
+
+  private int trimStartFrames;
+  private int trimEndFrames;
+  private boolean reconfigurationPending;
+
+  private int pendingTrimStartBytes;
+  private byte[] endBuffer;
+  private int endBufferSize;
+  private long trimmedFrameCount;
+
+  /** Creates a new audio processor for trimming samples from the start/end of data. */
+  public TrimmingAudioProcessor() {
+    endBuffer = Util.EMPTY_BYTE_ARRAY;
+  }
+
+  /**
+   * Sets the number of audio frames to trim from the start and end of audio passed to this
+   * processor. After calling this method, call {@link #configure(AudioFormat)} to apply the new
+   * trimming frame counts.
+   *
+   * @param trimStartFrames The number of audio frames to trim from the start of audio.
+   * @param trimEndFrames The number of audio frames to trim from the end of audio.
+   * @see AudioSink#configure(int, int, int, int, int[], int, int)
+   */
+  public void setTrimFrameCount(int trimStartFrames, int trimEndFrames) {
+    this.trimStartFrames = trimStartFrames;
+    this.trimEndFrames = trimEndFrames;
+  }
+
+  /** Sets the trimmed frame count returned by {@link #getTrimmedFrameCount()} to zero. */
+  public void resetTrimmedFrameCount() {
+    trimmedFrameCount = 0;
+  }
+
+  /**
+   * Returns the number of audio frames trimmed since the last call to {@link
+   * #resetTrimmedFrameCount()}.
+   */
+  public long getTrimmedFrameCount() {
+    return trimmedFrameCount;
+  }
+
+  @Override
+  public AudioFormat onConfigure(AudioFormat inputAudioFormat)
+      throws UnhandledAudioFormatException {
+    if (inputAudioFormat.encoding != OUTPUT_ENCODING) {
+      throw new UnhandledAudioFormatException(inputAudioFormat);
+    }
+    reconfigurationPending = true;
+    return trimStartFrames != 0 || trimEndFrames != 0 ? inputAudioFormat : AudioFormat.NOT_SET;
+  }
+
+  @Override
+  public void queueInput(ByteBuffer inputBuffer) {
+    int position = inputBuffer.position();
+    int limit = inputBuffer.limit();
+    int remaining = limit - position;
+
+    if (remaining == 0) {
+      return;
+    }
+
+    // Trim any pending start bytes from the input buffer.
+    int trimBytes = Math.min(remaining, pendingTrimStartBytes);
+    trimmedFrameCount += trimBytes / inputAudioFormat.bytesPerFrame;
+    pendingTrimStartBytes -= trimBytes;
+    inputBuffer.position(position + trimBytes);
+    if (pendingTrimStartBytes > 0) {
+      // Nothing to output yet.
+      return;
+    }
+    remaining -= trimBytes;
+
+    // endBuffer must be kept as full as possible, so that we trim the right amount of media if we
+    // don't receive any more input. After taking into account the number of bytes needed to keep
+    // endBuffer as full as possible, the output should be any surplus bytes currently in endBuffer
+    // followed by any surplus bytes in the new inputBuffer.
+    int remainingBytesToOutput = endBufferSize + remaining - endBuffer.length;
+    ByteBuffer buffer = replaceOutputBuffer(remainingBytesToOutput);
+
+    // Output from endBuffer.
+    int endBufferBytesToOutput = Util.constrainValue(remainingBytesToOutput, 0, endBufferSize);
+    buffer.put(endBuffer, 0, endBufferBytesToOutput);
+    remainingBytesToOutput -= endBufferBytesToOutput;
+
+    // Output from inputBuffer, restoring its limit afterwards.
+    int inputBufferBytesToOutput = Util.constrainValue(remainingBytesToOutput, 0, remaining);
+    inputBuffer.limit(inputBuffer.position() + inputBufferBytesToOutput);
+    buffer.put(inputBuffer);
+    inputBuffer.limit(limit);
+    remaining -= inputBufferBytesToOutput;
+
+    // Compact endBuffer, then repopulate it using the new input.
+    endBufferSize -= endBufferBytesToOutput;
+    System.arraycopy(endBuffer, endBufferBytesToOutput, endBuffer, 0, endBufferSize);
+    inputBuffer.get(endBuffer, endBufferSize, remaining);
+    endBufferSize += remaining;
+
+    buffer.flip();
+  }
+
+  @Override
+  public ByteBuffer getOutput() {
+    if (super.isEnded() && endBufferSize > 0) {
+      // Because audio processors may be drained in the middle of the stream we assume that the
+      // contents of the end buffer need to be output. For gapless transitions, configure will
+      // always be called, so the end buffer is cleared in onQueueEndOfStream.
+      replaceOutputBuffer(endBufferSize).put(endBuffer, 0, endBufferSize).flip();
+      endBufferSize = 0;
+    }
+    return super.getOutput();
+  }
+
+  @Override
+  public boolean isEnded() {
+    return super.isEnded() && endBufferSize == 0;
+  }
+
+  @Override
+  protected void onQueueEndOfStream() {
+    if (reconfigurationPending) {
+      // Trim audio in the end buffer.
+      if (endBufferSize > 0) {
+        trimmedFrameCount += endBufferSize / inputAudioFormat.bytesPerFrame;
+      }
+      endBufferSize = 0;
+    }
+  }
+
+  @Override
+  protected void onFlush() {
+    if (reconfigurationPending) {
+      // This is the initial flush after reconfiguration. Prepare to trim bytes from the start/end.
+      reconfigurationPending = false;
+      endBuffer = new byte[trimEndFrames * inputAudioFormat.bytesPerFrame];
+      pendingTrimStartBytes = trimStartFrames * inputAudioFormat.bytesPerFrame;
+    } else {
+      // This is a flush during playback (after the initial flush). We assume this was caused by a
+      // seek to a non-zero position and clear pending start bytes. This assumption may be wrong (we
+      // may be seeking to zero), but playing data that should have been trimmed shouldn't be
+      // noticeable after a seek. Ideally we would check the timestamp of the first input buffer
+      // queued after flushing to decide whether to trim (see also [Internal: b/77292509]).
+      pendingTrimStartBytes = 0;
+    }
+    endBufferSize = 0;
+  }
+
+  @Override
+  protected void onReset() {
+    endBuffer = Util.EMPTY_BYTE_ARRAY;
+  }
+
+}