Wednesday, December 9, 2009 at 11:49 pm
Why is there no Teletext in my HDTV?
I have been asked why there is no Teletext in some HDTV transmissions/streams like in ORF1HD and ORF2HD via aonTV. Personally I used to love browsing Teletext. I would just lie in front of the TV and click through the pages with color buttons or by entering the numbers directly. Of course one had to know that tonights TV program starts at 300, the weather at 600 and 460 is also sometimes interesting… but that was in the 90ties!
Today we have Internet everywhere. Teletext is a waste of bandwidth.
Anyway, it would still be possible to have Teletext with HDTV. The standardization of VBI data like DVB Teletext via MPEG-TS is valid (ETS 300-472) for SD and HD and there is room for VBI data in HD-SDI (SMPTE 292M-1998) known as the VANC and HANC data. There is however no global standard for VBI in HD-SDI. That leaves a gap in the signal processing chain from DVB-S/S2 source via receiver/descrambler/decoder via HD-SDI to encoder to MPEG-TS over IP stream. There are regional standardization efforts in SMPTE-2031 (ATSC countries) and OP-47 (Australia). [1]
Another thing: forget reading Teletext directly with your LCD/Plasma-TV. The times of the “Vertical Blanking Interval” are definitely over when using HDMI. There simply is no blanking interval in 720p oder 1080p. Instead EBU Tech-3333 describes “Teletext Services” as mandatory/recommended to be decoded, stored and displayed using the Settop Box (except with SCART). [2]
No. 1 — December 10th, 2009 at 8:01 am
well, having my computer (and internet) only 2 meters away from my tv and my iphone on the couchtable i still prefer looking at page 100 on teletext to see what i’m watching right now and what’s up next (most channels have this feature on teletext). looking it up on tvtv.at (on the mac) or in “tv select” (on the iphone) takes considerably longer and is much less comfortable than turning on teletext for 5 seconds.
No. 2 — December 10th, 2009 at 6:44 pm
that is of course a valid usecase… for analog tv… in the 90ties ;)
aontv, upc digital and almost all dvb-s & t receivers have a short and full epg to show this information onscreen. that’s why they added sending epg data via dvb.