AudioSource和VideoSource都是MediaSource的子類(lèi)，它們同樣是包裹在C++外的一層，它們的功能是承載一個(gè)或多個(gè)AudioTrack/VideoTrack。

//AudioSource完全繼承了父類(lèi)，并沒(méi)有任何的重寫(xiě)
public class AudioSource extends MediaSource {
  public AudioSource(long nativeSource) {
    super(nativeSource);
  }
}

//同樣是繼承了父類(lèi)的所有的方法，但是新增了一個(gè)方法是，適應(yīng)外界輸出的分辨率
public VideoSource(long nativeSource) {
    super(nativeSource);
  }

  /**
   * Calling this function will cause frames to be scaled down to the requested resolution. Also,
   * frames will be cropped to match the requested aspect ratio, and frames will be dropped to match
   * the requested fps. The requested aspect ratio is orientation agnostic and will be adjusted to
   * maintain the input orientation, so it doesn't matter if e.g. 1280x720 or 720x1280 is requested.
   */
  public void adaptOutputFormat(int width, int height, int fps) {
    nativeAdaptOutputFormat(nativeSource, width, height, fps);
  }

  private static native void nativeAdaptOutputFormat(
      long nativeSource, int width, int height, int fps);