Android 视频缩放/放大

1. 原理

不直接改变Codec输出的视频宽高比，而是改变视频播放器窗体的大小。

2. 设置Window

须要将Window设置未能够超出屏幕尺寸

mWindow.setFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS, WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);

3. SurfaceView保持宽高比

mSurfaceHolder.setFixedSize(mVideoWidth, mVideoHeight);

4. 改变Surface窗体大小

ViewGroup.LayoutParams layoutParams = (ViewGroup.LayoutParams) mSurface.getLayoutParams();
if (scale > 4.0f) {
    scale = 4.0f;
} else if (scale < 0.25f) {
    scale = 0.25f;
}
layoutParams.width = (int) (windowWidth * scale);
layoutParams.height = (int) (windowHeight * scale);

mSurface.setLayoutParams(layoutParams);