Microsoft DirectX 9.0

Line 21 Decoder Filter

This Line 21 Decoder filter decodes line 21 data and draws the caption text onto bitmaps.

The input pin connects to any line 21 data provider, typically either a DVD video decoder or the CC Decoder filter. The CC Decoder provides line 21 data from the VBI of an analog television signal. The output pin connects to a secondary pin on the Overlay Mixer or to another video renderer, such as the VMR.

This filter accepts line 21 data in the standard byte-pair format or, for DVD, as a packet for the whole group of pictures (GOP). For every GOP in the DVD video stream, there can be a user data packet that has that particular GOP's header information and line 21 data.

Two versions of this filter are available:

Filter CLSID
Line 21 Decoder CLSID_Line21Decoder
Line 21 Decoder 2 CLSID_Line21Decoder2

The version 1 filter is used on Microsoft® Windows® 9.x and Windows 2000 platforms. The version 2 filter is available only in Microsoft Windows XP, and is used whenever the Video Mixing Renderer is in the graph.

The information in the following table applies to both versions of the filter:

Filter Interfaces IAMLine21Decoder, IBaseFilter
Input Pin Media Types Major Type: MEDIATYPE_AUXLine21Data


  • MEDIASUBTYPE_Line21_BytePair (standard line 21)
  • MEDIASUBTYPE_Line21_GOPPacket (DVD line 21)

Format Type: FORMAT_VideoInfo or GUID_NULL.

Input Pin Interfaces IMemInputPin, IPin, IQualityControl
Output Pin Media Types Major type: MEDIATYPE_Video



Format Type: FORMAT_VideoInfo

Output Pin Interfaces IMediaPosition, IMediaSeeking, IPin, IQualityControl
Filter CLSID See previous table.
Property Page CLSID None
Executable qdvd.dll
Merit Line 21 Decoder: MERIT_NORMAL

Line 21 Decoder 2: MERIT_NORMAL + 2

Filter Category CLSID_LegacyAmFilterCategory

See Also