RE: On Screen Display - STV5730A IS being discontinued :-(

["Kevin Hawkins" <lists@xxxxxxx>]

Ah yes =96 the BBC days =96 when you could get at everything ea=
sily
! They occupy a box in my loft too accompanied by an Acorn Atom, a
Commodor=
e
Pet & several Compukit UK101=92s  =96 add a few Sinclair units and
Nascom=
=92s  to
flavour=85..

=20

What I=92d meant here was actually using a Teletext ENCODER chi=
p
to generate whatever signal is superimposed on a normal TV broadcast signal
(the actual data in the very first scan lines) =96 and then to make use of
=
the
internal Teletext decoders that are built into almost every TV as the on
screen display =96 using the subtitle bit as well if possible to get pop up
windows. What would be required is some clever switching to effectively
superimpose, interleave or substitute your own Teletext data for the
broadcast one. Sort of strip a few scan lines and insert some of your own I
guess. I just wondered if there was any practical or cost effective way of
doing this =96 probably not I suspect it=92s very expensive as it will be
l=
ow
volume on the encoder side.

It wouldn=92t have a nice facility for opacity in overlays eith=
er.

=20

Kevin

-----Original Message-----
From: Keith Doxey [mailto:ukha@xxxxxxx]=20
Sent: 12 June 2003 03:05
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] On Screen Display - STV5730A IS being discontinued
:-=
(

=20

Hi Kevin,

Back in the days of the BBC Micro, it had 8 different video modes using
varying amounts of the 32K ram available for both program and display. Mode
7 was the most frugal mode using only 1K of RAM for the whole screen. This
it did by having a teletext chipset in addition to its graphics controller.

I wrote most of my programs using Mode 7 and had a teletext feel to most of
the screens, down to the title bar which had a continuous data/time display
at the top.

At the time, I looked for suitable chipsets to to do the task but there
wer=
e
very few options as TV sets got more complex. Looking round the Philips
Semiconductor website last night for OSD chips I found that they also didnt
have any discrete OSD chips.

The tendancy now is to cram almost the whole TV or Monitor chipset into a
single LSI chip that deals with Tuning, Scannning, Teletext, other OSD etc.
Its one of the things that has emabled the price of TV's to plumet with a
manufacturer being able to offer a whole range of sets where the only
differences between the sets are the size of the cabinet and tube.

Part of the SCART specification relates to the use of Pin 16 (Fast
Blanking/RGB). This is the pin you must activate to allow RGB signals into
the TV. Normally this is also used with Pin 8 for allowing an external
source to override the internal tuner, but the STV5730A datasheet mentions
using it in RGB mode to allow coloured text to be overlaid. It does this by
taking the tuners output from SCART and locking the signal to it, then just
using the Fast Blanking pin to overlay the test.

People on the list have previously mentioned that they have accidently used
this "feature" of the SCART when they have had RGB equipment
connected but
havent actually selected Pin 8. Sadly, different TV manufacturers implement
the SCART standards in different ways so that functionality isnt always
guaranteed to work.

With the increase in low cost graphics cards and all in one motherboards
such as the VIA ITX board that have TV out there are other possibilities.
Using such a board at 640x480 would enable good quality text and graphics
t=
o
be sent to a TV by choosing a suitable font size that was optimised for TV
viewing.

To get a superb quality text and graphics display would require a graphics
card that could output at RGB instead of S-Video or Composite. The
difference would be like going from Tivo/Digibox menus as Composite to
menu=
s
as RGB. However, that would still lack the "Overlay" capability
that we
really need. To do that would mean that the graphics card would have to be
Genlocked to the existing Video screen. That was definately possible in the
days of the BBC Micro because the ones they used on the TV shows had been
modified with an external video input to lock the signal to. If I could
fin=
d
out what they did the I could re-use the 6 BBC B's that I have stored in
th=
e
loft!

Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: Kevin Hawkins [mailto:lists@xxxxxxx]
> Sent: 12 June 2003 01:10
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] On Screen Display - STV5730A IS being
> discontinued
> :-(
>
>
> Thinking laterally on this one =96 are there any chips that
> generate teletext
> information =96 in a way that you could use such a chip on a
> standard video
> source to insert your own teletext pages into a video signal
> ? Or is this
> really big kit / big bucks stuff.
>
> If there was a practical way of adding your pages into an existing TV
> broadcast signal either by substituting your page for an
> existing page =96 or
> even better a non existent but valid page then you could use
> the inbuilt
> teletext decoders as your overlay.  If you could simulate one of the
> subtitle pages that would be even more useful. Plus you
> wouldn=92t get the
> video deterioration that some of the other overlay systems
> introduced, and
> it might work over RGB =96 component and S-Video . I=92m guessing
> this is a non
> starter but =85..
>
>
>
> How about that as a project Keith ?? Would be a great =91Elektor=92
type
> project.
>
>
>
> Kevin
>
>
>
> -----Original Message-----
> From: Keith Doxey [mailto:ukha@xxxxxxx]
> Sent: 11 June 2003 19:09
> To: UKHA Discussion (E-mail)
> Subject: [ukha_d] On Screen Display - STV5730A IS being
> discontinued :-(
>
>
>
> Hi All,
>
> Been mentioned several times on the list in the past, not
> least because of
> doubts about the availability of the STV5730A.
>
> Yesterday I had a call from my account manager at Rapid
> Electronics and I
> asked her to find out pricing and availability of said
> chip... not good news
> :-(
>
> It IS being discontinued. It is currently on "Lifetime Buy"
> status where
> this is the last chance for people to buy all they will ever
> need for the
> lifetime of their product before it disappears forever. Even
> if you want to
> buy it at the moment it is on very long lead times.
>
> She did manage to find some stock, she could get me 2500 of
> them but the
> asking price was over =A36 each and they have to be bought in
> tubes of 28
> devices.
>
> I asked her to check if there was a replacement chip and the
> answer once
> again is NO.
>
> Presumably with the increase in TV/Computer convergence ala
> TiVo etc, there
> is little need for OSD chips as the graphics processors used
> in such devices
> handle all the overlay stuff as a matter of course.
>
> I also notice that http://www.stv5730a.co.uk  aka
BlackBox
> Camera Co still
> have their OSD boards available but no longer supply just the
> chips so that
> they can prolong the life of their product by keeping all the
> stocks for
> themselves.
>
> I did buy some chips from them a couple of years ago and they
> were only
> about =A35 each which is less than the current quantity trade price
:-(
>
> Looks like a video overlay device for xAP and xPL will need a bit of a
> redesign if it is to be a long term project.... sorry Frank!
>
> To sum it up in one word..... BUGGER !!!!!
>
> Keith
>
> www.diyha.co.uk
> www.kat5.tv
>
>
>
>
>
>
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