Line 21 Decoder Filter

This component is available for use in the Microsoft Windows 2000, Windows XP, and Windows Server 2003 operating systems. It may be altered or unavailable in subsequent versions.

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. The format of the byte pairs is defined in the EIA/CEA-608-B standard; please refer to that standard for more information.

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® 95/98/Me and Windows 2000 platforms. The version 2 filter is available in Microsoft Windows XP and later, 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_AUXLine21DataSubtype:
  • 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_VideoSubtype:
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_NORMALLine 21 Decoder 2: MERIT_NORMAL + 2
Filter Category CLSID_LegacyAmFilterCategory


DirectShow Filters

Closed Captions and Teletext

DVD Filter Graph Configuration