Add AudioGraph test verifying silence outputs correct amount of bytes.

PiperOrigin-RevId: 559072505

libraries/transformer/src/test/java/androidx/media3/transformer/AudioGraphTest.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2023 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 androidx.media3.transformer;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.media3.common.C;
+import androidx.media3.common.Format;
+import androidx.media3.common.MediaItem;
+import androidx.media3.common.MimeTypes;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import java.nio.ByteBuffer;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unit tests for {@link AudioGraph}. */
+@RunWith(AndroidJUnit4.class)
+public class AudioGraphTest {
+  @Test
+  public void silentItem_outputsCorrectAmountOfBytes() throws Exception {
+    EditedMediaItem item = new EditedMediaItem.Builder(MediaItem.EMPTY).build();
+    Format format =
+        new Format.Builder()
+            .setSampleRate(50_000)
+            .setChannelCount(6)
+            .setPcmEncoding(C.ENCODING_PCM_16BIT)
+            .setSampleMimeType(MimeTypes.AUDIO_RAW)
+            .build();
+
+    AudioGraph audioGraph = new AudioGraph(new DefaultAudioMixer.Factory());
+    GraphInput input = audioGraph.registerInput(item, format);
+
+    input.onMediaItemChanged(
+        item, /* durationUs= */ 3_000_000, /* trackFormat= */ null, /* isLast= */ true);
+    int bytesOutput = drainAudioGraph(audioGraph);
+
+    // 3 second stream with 50_000 frames per second.
+    // 16 bit PCM has 2 bytes per channel.
+    assertThat(bytesOutput).isEqualTo(3 * 50_000 * 2 * 6);
+  }
+
+  /** Drains the graph and returns the number of bytes output. */
+  private static int drainAudioGraph(AudioGraph audioGraph) throws ExportException {
+    int bytesOutput = 0;
+    ByteBuffer output;
+    while ((output = audioGraph.getOutput()).hasRemaining() || !audioGraph.isEnded()) {
+      bytesOutput += output.remaining();
+      output.position(output.limit());
+    }
+    return bytesOutput;
+  }
+}