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The IQualPropinterface is exposed by renderers, typically a video renderer, to return information about the performance achieved—for example, the number of frames per second (fps). The values returned through the interface are reset each time the filter is run. The base classes of the Microsoft DirectShow Software Development Kit (SDK) have a standard property page that displays the information available from this interface.
When to Implement
The IQualPropinterface is implemented by the DirectShow video renderer. Other video renderers might want to implement this interface as well, although it is optional.
When to Use
Applications use this interface to retrieve video renderer performance information.
Methods in Vtable Order
| IUnknown methods | Description |
|---|---|
| QueryInterface | Returns pointers to supported interfaces. |
| AddRef | Increments the reference count. |
| Release | Decrements the reference count. |
| IQualProp methods | Description |
| get_AvgFrameRate | Retrieves the average frame rate achieved. |
| get_AvgSyncOffset | Retrieves the average time difference between when a frame was due for rendering and when rendering actually began (this is returned as a value in milliseconds). |
| get_DevSyncOffset | Retrieves the average time difference between when a frame was due for rendering and when rendering actually began (this is returned as a standard deviation). |
| get_FramesDrawn | Retrieves the number of frames drawn since streaming started. |
| get_FramesDroppedInRenderer | Retrieves the number of frames dropped by the renderer. |
| get_Jitter | Expresses the average time between successive frames delivered to the video renderer. |