shadows/framework/src/main/java/org/robolectric/shadows/ShadowMediaMuxer.java
@Implementation
  protected static void nativeWriteSampleData(
      long nativeObject,
      int trackIndex,
      @NonNull ByteBuffer byteBuf,
      int offset,
      int size,
      long presentationTimeUs,
      @MediaCodec.BufferFlag int flags) {
    int toWrite = size - offset;
    byte[] bytes = new byte[toWrite];
    byteBuf.get(bytes, 0, toWrite);

    try {
      getStream(nativeObject).write(bytes);
    } catch (IOException e) {
      throw new RuntimeException("Unable to write to temporary file.", e);
    }
  }
@Implementation
  protected static void nativeWriteSampleData(
      long nativeObject,
      int trackIndex,
      @NonNull ByteBuffer byteBuf,
      int offset,
      int size,
      long presentationTimeUs,
      @MediaCodec.BufferFlag int flags) {
    int toWrite = size - offset;
    byte[] bytes = new byte[toWrite];
    byteBuf.get(bytes, 0, toWrite);

    try {
      getStream(nativeObject).write(bytes);
    } catch (IOException e) {
      throw new RuntimeException("Unable to write to temporary file.", e);
    }
  }
Writes the given data to the FileOutputStream for the associated muxer.