Classes of Analog TV Hardware Devices

In the context of building an analog TV filter graph, there are two basic classes of analog capture cards: (1) those that send the video data directly to video memory through a direct hardware connection called a video port, and (2) those that send the video data first to host memory via the PCI bus, or over a USB or IEEE 1394 connection, and then to the graphics card.

From an application's point of view, there are two basic differences in the filter graphs for video port devices and PCI/USB/1394 devices:

• Graphs based on video port devices will require an extra filter, the Video Port Manager. This filter is needed to allocate extra video memory on the video graphics adapter for the VBI bitmaps. It connects to the VPVBI output pin on the capture filter.
• Graphs based on video port devices will use the Bt829 capture filter and graphs based on PCI (and 1394/USB) devices will use the Bt848 capture filter. Graphs using the Bt848 filter will not use the Video Port Manager.