Remarks that grabbing samples using ISampleGrabber

最新推荐文章于 2011-02-27 12:23:00 发布

原创最新推荐文章于 2011-02-27 12:23:00 发布 · 1.2k 阅读

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本文探讨了SampleGrabber滤镜的一些使用限制，包括它不支持顶部到底部方向（负biHeight）的视频类型、FORMAT_VideoInfo2格式类型以及表面步长与视频宽度不符的情况。此外，还介绍了MediaDetector对象作为抓取位图的一种更简单方法。

R1.

The filter does not support video types with top-down orientation (negative biHeight) or with format type FORMAT_VideoInfo2. Also, it rejects any video type where the surface stride does not match the video width. This means that for some video types, the Sample Grabber will not connect to the Video Mixing Renderer (VMR).

R2.

If you simply want to grab a bitmap from a video file, it is easier to use the Media Detector (MediaDet) object. See Grabbing a Poster Frame for details. The Sample Grabber is more flexible, however, because it works with nearly any media type (see ISampleGrabber::SetMediaType for the few exceptions), and offers more control to the application.

R3.

Regardless of what type you set, the Sample Grabber Filter rejects any video types with top-down orientation (negative biHeight), or with a format type of FORMAT_VideoInfo2. In this case, although the SetMediaType method succeeds, the filter will not connect.