Microsoft DirectX 8.0 |
World Standard Teletext (WST) is the European standard for data transmission using VBI on PAL analog television signals. Both captioning and data services are provided using this standard. The WST Codec is a kernel-mode filter that receives raw VBI samples and, optionally, decoded Teletext samples from the Capture Filter via the Tee/Sink-to-Sink Converter filter. This codec decodes and/or duplicates the decoded and forward-error-corrected Teletext data for the WST Decoder filter. The WST Decoder then creates the bitmaps that are sent to the Overlay Mixer.
The WST Codec appears in GraphEdit in the "WDM Streaming VBI Codecs" category. Because this is a kernel-mode filter, applications cannot co-create it directly, but must use the System Device Enumerator to instantiate it, as described in Enumerating Devices and Filters.