excellent rant

I have to get a smart phone just to use a TV? Here I was about to get a TV... I'll put that off until smart phones have gone.

Yeah, they *use* TVs. My friend has been legally blind for some time now and has some favorite programs he hasn't given up. News for example...

What??? I believe the idea is that the unit "learns", not so much the user. Still, I think a standard remote would be preferable by those with vision problems.

Over here every program with foreign language audio is subtitled. There is a separate subtitle channel for use by blind people, which besides the normal translated spoken language also can provide scene descriptions. Blind people use it to drive a speech synthesizer to hear the programme's audio in their own language.

(in some other countries I have seen channels where scene descriptions, together with the normal audio, are available as a separate audio channel)

Don't be stupid. He said "you'd probably get away with...", and he's right. I have two HDMI inputs on my TV used and also use its WIFI but if there were only one HDMI input, it wouldn't be the end of the world. HDMI switches are pretty cheap and I'd probably have bought a home theater receiver with the switch built in, instead of a sound bar.

Just because he mentioned "smart phone" the Luddites go nuts.

Felt cheated, huh? ;-)

We've had "SAP" (secondary audio program) for some time. It is typically used to present, e.g., spanish language for the program.

Closed Captioning has been available even longer (~40 years?). (neighbors were Gallaudet allumni so being naturally curious, they were the horse's mouth)

It works best for prerecorded content as "live TV" requires live transcription (which is often hampered by typographical and other errors for which there simply is insufficient time to correct before the "next" word has to be transcribed).

The digital signal is encoded in the vertical blanking interval. With old analog TV's, you could patiently adjust the vertical hold to "roll" the blanking interval down onto the screen where you could see a changing series of white "dashes" interspersed in the otherwise "black" field.

Originally, a separate decoder box was required to extract the signal and present the text -- mixed back into the (RF) video. With the introduction of STB's and digital sets, the decoder became part of the TV itself. Many sets also give you the ability to control the visual presentation of that text.

There are several different closed caption "channels" available in the video stream (IIRC, 6?). These have differing content and all -- or none -- may be available in a given program.

This is somewhat common on prerecorded media (DVD's) as "Descriptive Video Service" (or something like that). If you don't "need" the capability, it can be difficult to get used to (if you elect to "try it" -- especially if you also have access to the closed captioning information AND the actual video content. It seems to be too much information for most folks to handle, simultaneously.

OTOH, it's an inexpensive way to get a feel for what a visually impaired person would have to put up with to enjoy the same content (just close your eyes!)

Probably not. It was the population that got stuck with Never The Same Colour Twice who were cheated. It's kind of like the US constitution - you seem to have to see how the system can go wrong before you can build one that works well.

Here in Europe such services are part of the Teletext service which has been available for the past 40 years (although currently more and more channels are phasing out the original "news and info" part of it), and indeed on analog it was sent as one or two lines with digital coding on it. But rarely anyone uses analog anymore, and now it is just a separate stream in the MPEG Transport Stream used to transmit the video and audio.

In this system the use of multiple audio programs is no problem at all, there can be as many as you like. E.g. there is a "european union information channel" that has like 16 audio programs associated with it, where the same press item can be presented in many languages.

For subtitling and scene description the parts to show it on the screen are present in every TV sold here, but to use the external synthesizer you need a special external box made for this purpose.

It is available on state TV channels in some European countries. (commercial channels normally don't provide this service - the programs they transmit are only fillers between the commercial messages they want to sent, so the average viewer won't zap away and miss the commercials. viewers with special needs are not of interest to them, so they don't cater for that. State TV is different, or at least used to be)

I have sometimes listened to it, e.g. on BBC. You can have the TV on without watching all the time :-)

Initially there was two Teletext lines on each field (100 lines/s total), but later nearly all unused lines above the active picture was used for Teletext, reducing the update time considerably.

Depends on the country and company.

Teletext subtitling was popular especially with analog satellite operators, which might have a half a dozen languages within the satellite footprint. The subtitles for different languages were inserted into different Teletext pages and the only thing that the viewer had to do was to select the correct Teletext page which automatically put the TV into "mixed" mode (video+Teletext).

These days DVB subtitling is used, in which the subtitles are sent as separate bit map (2 level) images. In fact any bit map images (such as glyphs for any writing system) could be used. There can be several such bit maps for different languages in a Transport Stream and the user selects which language (if any) is mixed with the video.

The DVB bitmap contains a time stamp when the image should be shown and removed. Some early receivers did not handle DVB subtitling at all, some handled the timestamp erroneously, causing early or late display of subtitling and a few required a huge amount of time to process the bitmap. For this reasons, some broadcasters sent these bitmaps several seconds in advance. This is annoying since zapping between channels, the subtitling appears several seconds after the zap.

This was not done here... but I have a receiver that buffers all teletext pages for a channel even when teletext is not shown, so when hitting the teletext button after being tuned to the channel for some time, all pages (including rotating pages) are available immediately. This is IMHO very necessary to use the service comfortably.

I know about that system, it is used in some countries here, but not in my own country. Here the subtitles are either embedded in the video or sent separately as teletext. It would be better if they were never embedded and sent in the DVB subtitling system instead, as this allows everyone to select their preferred way (subtitles off or another language).

My receiver can display teletext subtitles in the same rendering quality as those embedded or DVB subtitles typically have. But not all receivers can do that, many still display them in the classical teletext font or a slight improvement thereof, and have difficulty with readability on some backgrounds (unless you have that ugly bad box)

My receiver does that too.

Unfortunately it is a bit dumb, when there are multiple video streams and a single common Teletext stream in the same transport stream, zapping between video streams in the same TS requires waiting for the Teletext stream to reload :-)

The DVB subtitling easily handles .e.g. various Latin or Cyrillic fonts even on the same subtitle line. However, with SD and HD simulcasts, there is the question, at what size should the subtitles be displayed. The best solution would be that the viewer could zoom the subtitles.

Same here, but with external STB/recorder with SD resolution selected, this might not be the case. With a HD display and STB/recorder displaying SD material, it is usually better to have the STB-TV link set to HD all the time and let the STB/recorder do the upconversion, this should not be an issue.

Does any Teletext receiver still use the 7x9 matrix font ?? For semigraphics, 2x3 bit map is still used.

I think that is a reason why it is not used here. (HD viewers complaining about small subtitles)

My receiver does that all the time. It outputs 1920x1080 over HDMI and YPbPr and upscales SD. This has the added advantage that I can select in detail what it should do with 4:3 SD material, so I don't have to use the crappy format conversion in my TV. (I prefer to see 4:3 material in "pillarbox", i.e. with black bars on the sides, while the manufacturer of my TV preferred to use the entire screen area and implemented some nonlinear scaling that makes the picture look like the TV is defective)

It will usually be a a larger matrix, that is why I mentioned "slight improvement". However my receiver has much nicer fonts with anti-aliasing and also an automatic "shadow" added when the programme material is bright, so you can still see the characters. It does not do that when overlaying normal teletext over the picture. There I can select a black box to display the subtitles, as was standard on early teletext TVs, but that looks even more ugly.

There's a reason why NTSC was referred to as "Never Twice the Same Color".

--sp