Text capture: Difference between revisions
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The PAL standard uses teletext, while the NTSC standard uses closed captioning. |
The PAL standard uses teletext, while the NTSC standard uses closed captioning. |
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TV capture chipsets implement these in different ways, and the code to support text capture is still missing or incomplete on some chipsets. |
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Finally, different applications implement support in different ways. The following notes are just a start to describe the current state of affairs. |
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Revision as of 06:57, 22 April 2005
The PAL standard uses teletext, while the NTSC standard uses closed captioning. TV capture chipsets implement these in different ways, and the code to support text capture is still missing or incomplete on some chipsets. Finally, different applications implement support in different ways. The following notes are just a start to describe the current state of affairs.
Applications
ntsc-cc
The application ntsc-cc handles closed captioning on bttv devices. For ntsc-cc to work, you typically need to be running an application for viewing or recording television, such as xawtv and mencoder. If no such application is running, ntsc-cc tends to produce garbled output.
tvtime support for closed captioning
tvtime has built-in support for closed captioning for bttv and saa7134 cards (also other?).
In early 2004, Kevin Ko wrote a patch with useful comments to tvtime's vbidata.c; see his detailed account and the tvtime bugreport.
Unsupported cards
There is currently no code supporting closed captioning on cx88 cards.