4/3/2023 0 Comments Closed captionThis example uses the ICaptureGraphBuilder2::FindInterface method to locate the IAMLine21Decoder interface. PLine21->SetServiceState(AM_L21_CCSTATE_Off) &LOOK_DOWNSTREAM_ONLY, // Look downstream from pCap For example, you can turn off the captioning display using the IAMLine21Decoder::SetServiceState method, as follows: // Use the FindInterface method to find the interface. To control the captioning display, use the IAMLine21Decoder interface on the Line 21 Decoder filter. The following diagram shows a filter graph with the VBI Surface Allocator. The RenderStream method adds this filter if it is required. This pin must be connected to the VBI Surface Allocator filter, which allocates surfaces to hold the captured VBI data. If the capture device uses a video port, the capture filter might have a video port VBI pin (PIN_CATEGORY_VIDEOPORT_VBI). New applications should use the VBICodec filter, which is documented in the Microsoft TV Technologies documentation. The CC Decoder filter was removed in Windows Vista. If the capture filter has a CC pin instead of a VBI pin, the CC pin is connected directly to the Line 21 Decoder filter. The Capture Graph Builder's RenderStream method adds these filters automatically. The downstream filter (in this case the Overlay Mixer) overlays the bitmaps onto the video. Translates the CC byte pairs and draws the caption text onto bitmaps. Decodes CC data from the sampled VBI waveforms provided by the capture filter. Microsoft provides VBI codecs for Closed Caption, NABTS, and World Standard Teletext (WST). Accepts the VBI information from the capture filter and splits it into separate streams for each of the data services present on the signal. This graph uses the following filters for closed caption display: The following diagram shows a typical filter graph for displaying closed captions. Hr = pBuild->RenderStream(&PIN_CATEGORY_CC, 0, pCap, 0, 0) hr = pBuild->RenderStream(&PIN_CATEGORY_VBI, 0, pCap, 0, 0) To preview closed captions, call ICaptureGraphBuilder2::RenderStream with the VBI pin category, and if that fails, call it again with the CC category.
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