IMediaDet Interface

The IMediaDet interface retrieves information about a media file, such as the number of streams, and the media type, duration, and frame rate of each stream. It also contains methods for retrieving poster frames from a video stream.

The Media Detector (MediaDet) object exposes this interface.

To obtain information about a file using this interface, perform the following steps:

1. Create an instance of the Media Detector by calling CoCreateInstance. The class ID is CLSID_MediaDet.
2. Call IMediaDet::put_Filename to specify the name of the source file. (Alternatively, call IMediaDet::put_Filter.)
3. Call IMediaDet::get_OutputStreams to obtain the number of output streams in the source.
4. Call IMediaDet::put_CurrentStream to specify a particular stream.
5. Call any of the following methods: IMediaDet::get_StreamType, IMediaDet::get_StreamMediaType, IMediaDet::get_StreamLength, or IMediaDet::get_FrameRate.

To retrieve poster frames, call IMediaDet::GetBitmapBits or IMediaDet::WriteBitmapBits. Alternatively, call IMediaDet::EnterBitmapGrabMode and then IMediaDet::GetSampleGrabber to obtain a pointer to the ISampleGrabber interface. All three of these methods put the media detector into a new mode, called bitmap grab mode. The informational methods described previously do not work in this mode. Therefore, obtain any information you need before retrieving poster frames, or else create new instances of the media detector for each stream.

The IMediaDet interface does not support VIDEOINFOHEADER2 formats, so you cannot use this interface to get interlaced fields or information about interlacing. Also, if the upstream decoder supports only VIDEOINFOHEADER2, you cannot use IMediaDet. This might be the case with an MPEG-2 decoder, for example.

Requirements

Requires Qedit.h.

In addition to the methods inherited from IUnknown, the IMediaDet interface exposes the following methods.