Green square in top right corner of TV screen?
Flingle Bunt
Last night while watching Trust on BBC 1 (analogue off Sutton
Coldfield/Kidderminster transposer)I saw a green square appear and
disappear in the top right hand corner of the screen. Anybody else see
it, or know what it was? I thought it was an MPEG proplem at first but
it was too small,stable and seemed to happen at a scene boundary.
John.
P.S Off thread, durring the cold snap we had recently, why didn't the
frost form on the tarmac over the cable TV ducting? RF heating pehaps?
Mark Carver
"Flingle Bunt" <john....@ntl.com> wrote in message
news:334be06d.03011...@posting.google.com...
> Hi All.
>
> Last night while watching Trust on BBC 1 (analogue off Sutton
> Coldfield/Kidderminster transposer)I saw a green square appear and
> disappear in the top right hand corner of the screen. Anybody else see
> it, or know what it was? I thought it was an MPEG proplem at first but
> it was too small,stable and seemed to happen at a scene boundary.
Didn't see that watching on D-Sat. The Beeb used to use cue dots top left
for tallying live studios and OBs? but I've not seen them for a few years now.
> P.S Off thread, during the cold snap we had recently, why didn't the
> frost form on the tarmac over the cable TV ducting? RF heating perhaps?
Phantom power maybe? Also don't BT blow compressed air into their ducts
from the exchange end to keep moisture out ?
Ian Clark
> Hi All.
>
> Last night while watching Trust on BBC 1 (analogue off Sutton
> Coldfield/Kidderminster transposer)I saw a green square appear and
> disappear in the top right hand corner of the screen. Anybody else see
> it, or know what it was? I thought it was an MPEG proplem at first but
> it was too small,stable and seemed to happen at a scene boundary.
If the right bit of a mpeg block is lost some decoders do default to
just displaying it solid green. Approximately how big was it?
> P.S Off thread, durring the cold snap we had recently, why didn't the
> frost form on the tarmac over the cable TV ducting? RF heating pehaps?
New tarmac is slightly water repellant, might explain it if the cable
was put in recently.
JohnandRhiannon
>
>P.S Off thread, durring the cold snap we had recently, why didn't the
>frost form on the tarmac over the cable TV ducting? RF heating pehaps?
>
This is a result of the build up of dropped frames in the duct. From time to
time these will be ignited by a realy hot piece of porn and the duct will
smolder for weeks!
Matthew Sylvester
news:b08p8u$eu9$1$8302...@news.demon.co.uk...
> Flingle Bunt wrote:
> > Last night while watching Trust on BBC 1 (analogue off Sutton
> > Coldfield/Kidderminster transposer)I saw a green square appear and
> > disappear in the top right hand corner of the screen. Anybody else see
> > it, or know what it was? I thought it was an MPEG proplem at first but
> > it was too small,stable and seemed to happen at a scene boundary.
>
> If the right bit of a mpeg block is lost some decoders do default to
> just displaying it solid green. Approximately how big was it?
If it was seen on analogue, then it would be unlikely to be an mpeg
artefact...
Steve
news:b09bj4$acf$1...@nntp0.reith.bbc.co.uk...
There is every possibiliy that the digital transmission could have been used
somewhere along the path.
>
>
Matthew Sylvester
"Steve" <st...@spamtrap.org> wrote in message
news:b09f0k$mvopk$1...@ID-155449.news.dfncis.de...
> "Matthew Sylvester" <mss...@yahoo.co.uk> wrote
> > If it was seen on analogue, then it would be unlikely to be an mpeg
> > artefact...
>
> There is every possibiliy that the digital transmission could have been
used
> somewhere along the path.
Digital yes, mpeg no.
Dave Liquorice
>> P.S Off thread, during the cold snap we had recently, why didn't
>> the frost form on the tarmac over the cable TV ducting? RF heating
>> perhaps?
How long ago was the cabling laid? The replacement backfill will have
different thermal properties to the orginal ground. Also the different
surface will have different properties with regards formation of dew
and thus frost. I've seen the opposite over trenches, frost on the
trench line but not on the adjacent ground.
> Phantom power maybe?
If they are losing enough power to prevent frost no wonder the cable
TV companies keep going bust/taken over.
> Also don't BT blow compressed air into their ducts from the exchange
> end to keep moisture out ?
Not the ducts but some paper insulated cables are pressurised with dry
nitrogen to prevent water ingress. They do use compressed air to blow
fibre down the ducting though.
--
Cheers new...@howhill.com
Dave. Remove "spam" for valid email.
Flingle Bunt
> > Hi All.
> >
> > Last night while watching Trust on BBC 1 (analogue off Sutton
> > Coldfield/Kidderminster transposer)I saw a green square appear and
> > disappear in the top right hand corner of the screen. Anybody else see
> > it, or know what it was? I thought it was an MPEG proplem at first but
> > it was too small,stable and seemed to happen at a scene boundary.
>
> If the right bit of a mpeg block is lost some decoders do default to
> just displaying it solid green. Approximately how big was it?
>
Hi Again.
The block was quite small possibly 8 by 8, but I thought with it been
green it would have been 16 by 16, not sure, if 4:2:2 level? I know
more about the audio bit than the picture bit.
TV is just really wireless with pictures,
It'll never catch on you know.
John
Stephen Neal
334be06d.03011...@posting.google.com, "Flingle Bunt"
<john....@ntl.com> wrote:
> Ian Clark <ya...@cows.yarn.org.uk> wrote in message
> news:<b08p8u$eu9$1$8302...@news.demon.co.uk>...
>> Flingle Bunt wrote:
>>> Hi All.
>>>
>>> Last night while watching Trust on BBC 1 (analogue off Sutton
>>> Coldfield/Kidderminster transposer)I saw a green square appear and
>>> disappear in the top right hand corner of the screen. Anybody else see
>>> it, or know what it was? I thought it was an MPEG proplem at first but
>>> it was too small,stable and seemed to happen at a scene boundary.
>>
>> If the right bit of a mpeg block is lost some decoders do default to
>> just displaying it solid green. Approximately how big was it?
>>
>
The green block could also have been added by BBC Birmingham - checking that
they were opted out of Network before the Ten O'Clock News?
BBC Cambridge used to use a little white square bottom right (to avoid
confusing Obs who may have been expecting Pres cue dots top of screen - now
unused...) This was used to confirm that the vision mixer in Cambridge was
in-circuit to the transmitter, by monitoring off-air.
Steve
Steve
Don't some analogue relays get feed via DSAT?
Matthew Sylvester
Not BBC ones, no. In this case as the original posting said the programme
was watched from the Kidderminster analogue relay which rebroadcasts Sutton
Coldfield.
Mark S
All BBC analogue TV services are derived from the digital services. The
outputs for DSat and DTT are simply arced to the correct aspect ratio in the
digital transmission suites and fed to the transmitters. The programmes etc
are stored on servers which are MPEG2.
Mark.
Matthew Sylvester
news:b0bvqf$nvnbl$1...@ID-83117.news.dfncis.de...
> All BBC analogue TV services are derived from the digital services. The
> outputs for DSat and DTT are simply arced to the correct aspect ratio in
the
> digital transmission suites and fed to the transmitters. The programmes
etc
> are stored on servers which are MPEG2.
Ok, but I wouldn't call the server part of the transmission chain as such.
Obviously a playout server is an error-less medium (excepting major
failures) and wouldn't create the sort of artifact we are discussing. Once
the signal has left the server as SDI there is no mpeg in the chain (or
indeed any dct-based compression which could give similar effects).
Besides, an mpeg error would almost certainly show up as a brief flash (no
more than one GOP i.e. approx 0.5s) rather than a static square. Even
continual errors would show up in different parts of the picture.
Are we bored yet? ;-)
Paul Ratcliffe
> All BBC analogue TV services are derived from the digital services. The
> outputs for DSat and DTT are simply arced to the correct aspect ratio in the
> digital transmission suites and fed to the transmitters. The programmes etc
> are stored on servers which are MPEG2.
What bitrate do these servers use?
Flingle Bunt
Hi Again
I posted the above couple of week ago, last night while watching
"Trust" on BBC1 (same reception conditions as last time) I saw the
green square again at about 21:35, this time accompanied by a brief
change in sound quality (severe LF cut). I've watched other programmes
at this time of night on BBC1 and I have only noticed this square on
this programme at this time. Is it on the sourse material, or does the
analogue distribution system reconfigure it self at this time, but
only on Thursdays?????
Cheers
John
Stephen Neal
334be06d.03013...@posting.google.com, "Flingle Bunt"
<john....@ntl.com> wrote:
As I posted before - I think you will find it is a test signal inserted to
demonstrate that an "opt-out" from Network has successfully taken place.
The green square is inserted into the incoming network signal, probably in
the mixer of the regional studio, then the output of this studio is switched
to the transmitters, rather than the direct feed of network. This tests
that the opt-out switching is working correctly. (Though not on DTT for
network red-light reasons)
This allows a test of regional opt-ing kit, without disrupting the content
of the channel. The LF cut is probably due to the network sound going into
and out of an analogue sound desk in the studio (and being decoded and
recoded to DSIS for the NICAM feed?)
BBC Cambridge used to use the same technique to test their opt-out gear
(though it was a white square bottom left) and BBC North West insert cue
dots I believe.
Steve