1 files changed, 99 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/audio/ChannelMappingAudioProcessor.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/audio/ChannelMappingAudioProcessor.java
new file mode 100644
index 0000000000..e8496d4608
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/audio/ChannelMappingAudioProcessor.java
@@ -0,0 +1,99 @@
+/*
+ * 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 androidx.annotation.Nullable;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Assertions;
+import java.nio.ByteBuffer;
+
+/**
+ * An {@link AudioProcessor} that applies a mapping from input channels onto specified output
+ * channels. This can be used to reorder, duplicate or discard channels.
+ */
+@SuppressWarnings("nullness:initialization.fields.uninitialized")
+/* package */ final class ChannelMappingAudioProcessor extends BaseAudioProcessor {
+
+  @Nullable private int[] pendingOutputChannels;
+  @Nullable private int[] outputChannels;
+
+  /**
+   * Resets the channel mapping. After calling this method, call {@link #configure(AudioFormat)} to
+   * start using the new channel map.
+   *
+   * @param outputChannels The mapping from input to output channel indices, or {@code null} to
+   *     leave the input unchanged.
+   * @see AudioSink#configure(int, int, int, int, int[], int, int)
+   */
+  public void setChannelMap(@Nullable int[] outputChannels) {
+    pendingOutputChannels = outputChannels;
+  }
+
+  @Override
+  public AudioFormat onConfigure(AudioFormat inputAudioFormat)
+      throws UnhandledAudioFormatException {
+    @Nullable int[] outputChannels = pendingOutputChannels;
+    if (outputChannels == null) {
+      return AudioFormat.NOT_SET;
+    }
+
+    if (inputAudioFormat.encoding != C.ENCODING_PCM_16BIT) {
+      throw new UnhandledAudioFormatException(inputAudioFormat);
+    }
+
+    boolean active = inputAudioFormat.channelCount != outputChannels.length;
+    for (int i = 0; i < outputChannels.length; i++) {
+      int channelIndex = outputChannels[i];
+      if (channelIndex >= inputAudioFormat.channelCount) {
+        throw new UnhandledAudioFormatException(inputAudioFormat);
+      }
+      active |= (channelIndex != i);
+    }
+    return active
+        ? new AudioFormat(inputAudioFormat.sampleRate, outputChannels.length, C.ENCODING_PCM_16BIT)
+        : AudioFormat.NOT_SET;
+  }
+
+  @Override
+  public void queueInput(ByteBuffer inputBuffer) {
+    int[] outputChannels = Assertions.checkNotNull(this.outputChannels);
+    int position = inputBuffer.position();
+    int limit = inputBuffer.limit();
+    int frameCount = (limit - position) / inputAudioFormat.bytesPerFrame;
+    int outputSize = frameCount * outputAudioFormat.bytesPerFrame;
+    ByteBuffer buffer = replaceOutputBuffer(outputSize);
+    while (position < limit) {
+      for (int channelIndex : outputChannels) {
+        buffer.putShort(inputBuffer.getShort(position + 2 * channelIndex));
+      }
+      position += inputAudioFormat.bytesPerFrame;
+    }
+    inputBuffer.position(limit);
+    buffer.flip();
+  }
+
+  @Override
+  protected void onFlush() {
+    outputChannels = pendingOutputChannels;
+  }
+
+  @Override
+  protected void onReset() {
+    outputChannels = null;
+    pendingOutputChannels = null;
+  }
+
+}