[mythtv] [experimental patch] vbi decoder for IVTV cards
staffan.pettersson at sverige.nu
Wed Mar 2 21:21:51 UTC 2005
> Got the patch applied now thanks, first impressions of actual decoding
> is very good. Current issues I have, sorry don't have time to
> investigate much, but thought you might like the feedback:
> Using Hauppauge PVR-350 for recording, playback using EPIA TV-out
> (Unichrome & Software).
> So the only relevant one may be:
> 1) 888 subtitles are not 100%, this could be reception issues -
> difficult to tell, however my picture is crystal clear and other txt
> pages I tried did not present any typical bad reception type errors.
> Other comments (This is my first experience of TText on Myth so these
> comments may be more general?)
> 2) Text fonts/colours (obviously only grey scale when using
> Unichrome), I presume just a matter of tweeking the theme? But when
> using software decoding impossible to read without contrasting
> 3) OSD offsets do not work for me, so text is often off the right of the
> 4) Using XvMC_VLD Unichrome decoding, has the usual performance issues
> with heavy use of OSD - but then this has nothing to do with your
> Anyway must dash,
> On Tue, 1 Mar 2005 22:47:58 +0100, Martin Barnasconi
> <mythtv at barnasconi.net> wrote:
>> Here the first experimental patch for the vbi decoding for PVR cards
>> using the
>> IVTV drivers. Although its far from perfect (that's why it's classified
>> experimental;-) it gives you some idea how things are implemented and I
>> challenge you to contribute to fill in the missing gaps or to improve
>> What it does:
>> it relies on having embedded vbi in the MPEG stream as defined in the
>> doc's. The embedded vbi stream includes the magic cookies "itv0' and
>> to mark the beginning of a vbi private stream. That's why some
>> lines are added to the avformatdecoder and ffmpeg decoder classes, to
>> recognize a vbi data steam. If detected, it will start decoding in the
>> vbidecoder class. An additional OSD overlay osdtypeteletext is used for
>> teletext and subtitles. Whole process is controlled from tv_play
>> Pages are updated after receiving new content, so even subtitling pages
>> 888) do work!
>> What it does not do yet (TODO ;-)
>> - It overrules the 'T' key for teletext/CC for non-encoder cards
>> (bttv/saa7134) . The original vbi code (part of
>> is still in, but I rather see this becoming part of this new vbidecoder
>> class. Like to see 'C' for CC/subtitles and 'T' for teletext. Problem:
>> function already in use...
>> As some people have a mixed PVR/bttv setup, we should detect which card
>> operational and select the correct vbi decoder.
>> - CC is not working yet, as we do not have this here in Europe. Please
>> the results in ccbuffer and in your stderr terminal and please report
>> - Teletext is text-only. No mosaic or other fancy stuff like blanking,
>> blicking, reveal functions yet. Uses current CC_font in OSD. Should be
>> teletext font in future. for the OSD overlay, we suffer from the color
>> mapping of YUV420 here. Use a font with sufficient width (eg bold fonts)
>> be able to read the blue or red text.
>> - other embedded data like WSS/PIL/CNI/VPS/PDC captured but not used.
>> Framework in place, detection and corresponding actions (e.g. signals
>> slots) to be defined.
>> - TT OSD overlay is now transparent. Future work is to have black,
>> transparent, or even left-TV/right-TT (for 16:9 screens) or TT-PIP
>> implemented (for big screens)
>> Give it a try and report your findings. Improvements are very welcome.
>> mythtv-dev mailing list
>> mythtv-dev at mythtv.org
> mythtv-dev mailing list
> mythtv-dev at mythtv.org
Can this be implimented for dvb to? I't would be great if someone make
this work, many channels of my provider sends teletext subs.
More information about the mythtv-dev