VideoInfo2 Format Type
A preview pin's preferred media type might be a type with a VIDEOINFOHEADER2 format. This format structure supports special features such as interlaced video and picture aspect ratios.
The VMR-7 and the VMR-9 both support VIDEOINFOHEADER2 directly. When you connect the VMR to the decoder, they will negotiate the best format. The older Video Renderer filter, however, does not support VIDEOINFOHEADER2. To use VIDEOINFOHEADER2 format types with the Video Renderer filter, you must insert the Overlay Mixer filter into the graph.
- Enumerate the preferred media types on the decoder filter's output pin, using the IPin::EnumMediaTypes method.
- Check the first media type in the enumeration sequence.
- If the format type is FORMAT_VideoInfo2, connect the output pin to the Overlay Mixer. Then connect the Overlay Mixer to the video renderer. (See Video Port Pins.)
If you do not care about these features, you do not have to use the Overlay Mixer. Connect the decoder directly to the Video Renderer, and it will connect with a VIDEOINFOHEADER format instead.