用mcisendstring实现一个简单的播放AVI的播放器。可以定位到某一特定的帧，同时可以把该帧截图保存为一个bmp文件。-Mcisendstring with the player to achieve a simple AVI player. Can be targeted to a particular fr a me, the fr a me at the same time can be saved as a bmp screenshot file.