WST Codec Filter

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]


This component has been removed from Windows Vista and later operating systems. It is available for use in the Microsoft Windows 2000, Windows XP, and Windows Server 2003 operating systems.


Starting in Windows Vista, this filter is replaced by the VBICodec filter, which is documented in the Microsoft TV Technologies documentation.

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 Codec corresponds to the CC Decoder filter for NTSC transmissions. The WST Decoder corresponds to the Line 21 Decoder for NTSC; these filters create the bitmaps that are sent to the Overlay Mixer or the Video Mixing Renderer.

This filter has two input pins, VBI and HWCC. The VBI pin is used for raw VBI data, and the HWCC pin is used when the VBI decoding is performed in hardware by the capture filter. When the data is received on the HWCC pin, the WST Codec operates in "pass-through" mode, and sends the data directly to the WST Decoder without processing it in any way. If the capture filter exposes an HWCC pin, it must be connected directly to the corresponding pin on the WST Codec.

The WST Codec filter appears in the "WDM Streaming VBI Codecs" filter category (AM_KSCATEGORY_VBICODEC).

Because this is a kernel-mode filter, applications cannot create it directly using CoCreateInstance. Instead, use the System Device Enumerator. For more information, see Creating Kernel-Mode Filters.

DirectShow Filters

Viewing World Standard Teletext