I took courses in colour TV during the middle to late sixties.
I understood Walter Bruch's PAL system and our 625 line variant.
But I honestly never troubled to find out how our digital TV system works.
Can someone point me to a sort of "UK Digital TV for geriatrics" that might be helpful?
TIA, Alan
Google the usual best bet - DVB for Dummies? (DVB is the technical
name for UK DTTV.)
If that spurs you on and you want to research
HD then its DVB-T2.
On Sat 29/10/2022 18:54, pinnerite wrote:
I took courses in colour TV during the middle to late sixties.
I understood Walter Bruch's PAL system and our 625 line variant.
But I honestly never troubled to find out how our digital TV system
works.
Can someone point me to a sort of "UK Digital TV for geriatrics" that
might be helpful?
Google the usual best bet - DVB for Dummies? (DVB is the technical name
for UK DTTV.) If that spurs you on and you want to research HD then its DVB-T2.
The connection between T2 and HD is a political decision there is no technical link. You can transmit HD on DVB-T without issue, I know,
I'm doing it.
In article <tjjqfd$3k5oe$1@dont-email.me>,
Woody <harrogate3@ntlworld.com> wrote:
Google the usual best bet - DVB for Dummies? (DVB is the technical
name for UK DTTV.)
Yes.
If that spurs you on and you want to research
HD then its DVB-T2.
Not really.
The connection between T2 and HD is a political decision there is no technical link. You can transmit HD on DVB-T without issue, I know,
I'm doing it.
"Bob Latham" <bob@sick-of-spam.invalid> wrote in message news:5a3f21cdbabob@sick-of-spam.invalid...
The connection between T2 and HD is a political decision there is no
technical link. You can transmit HD on DVB-T without issue, I know,
I'm doing it.
And conversely T2 can be (and is) used for sub-SD channels - ie 544x576 rather than 720x576. PSB3 has 5Select and TBN, and COM7 and COM8 used to
have some sub-SD channels. In fact all the T2 multiplexes had a mixture of
HD and sub-SD but no "full" SD.
It's the same as DVDs can have HD content and BluRays can have SD content. Software players such as VLC will happily play a DVD with HD content (if
you burn the DVD yourself) though I wonder if a dedicated BluRay (and DVD) player will play it.
In article <tjjqfd$3k5oe$1@dont-email.me>,
Woody <harrogate3@ntlworld.com> wrote:
Google the usual best bet - DVB for Dummies? (DVB is the technical
name for UK DTTV.)
Yes.
If that spurs you on and you want to research
HD then its DVB-T2.
Not really.
The connection between T2 and HD is a political decision there is no technical link. You can transmit HD on DVB-T without issue, I know,
I'm doing it.
Bob.
On Sat 29/10/2022 20:59, Bob Latham wrote:
In article <tjjqfd$3k5oe$1@dont-email.me>,
Woody <harrogate3@ntlworld.com> wrote:
Google the usual best bet - DVB for Dummies? (DVB is the technical
name for UK DTTV.)
Yes.
If that spurs you on and you want to research
HD then its DVB-T2.
Not really.
The connection between T2 and HD is a political decision there is no
technical link. You can transmit HD on DVB-T without issue, I know,
I'm doing it.
I am talkjng here about the UK situation. I don't dispute that there are other possibilities but I am replying - hence the insertion of UK - about
how we use it here!!
"Woody" <harrogate3@ntlworld.com> wrote in message news:tjjqfd$3k5oe$1@dont-email.me...
On Sat 29/10/2022 18:54, pinnerite wrote:
I took courses in colour TV during the middle to late sixties.
I understood Walter Bruch's PAL system and our 625 line variant.
But I honestly never troubled to find out how our digital TV system
works.
Can someone point me to a sort of "UK Digital TV for geriatrics" that
might be helpful?
Google the usual best bet - DVB for Dummies? (DVB is the technical name
for UK DTTV.) If that spurs you on and you want to research HD then its
DVB-T2.
If you have the ability to record a DVB data stream to a PC file (eg using NextPVR, TVHeadend or VLC and a DVB-USB tuner), and you are really
fascinated by the technicalities of DVB, I can recommend a free utility called TSReaderLite (Windows only). This is a cut-down version of a
version that costs money.
It shows you all the various tables in the DVB stream which a TV uses when
it does its initial tune/scan and then saves the information to its local memory so when you ask for BBC1 the TV knows which frequency to tune to,
and the stream IDs for video, programme sound, audio description sound, subtitles. There's also TVCapture, made by the same company that makes NextPVR, which can record a 1-minute sample of any DVB multiplex - so you
get all the channels that are contained in the mux. VLC (Media | OPen
Capture Device, Capture mode=TV-digital, Transponder/mux frequency=482,000 (kHz) can tune to any mux (if you have a tuner) and can then record the
whole mux indefinitely. (Substitute one of your correct mux frequencies
where I've written 482,000).
One thing to be aware of: digital SD uses 720x576 because these numbers
are compatible with 625-line analogue TV, which had 575 lines of picture
(the rest was sync pulses) and the bandwidth gave a horizontal resolution (for an old 4:3 frame) of about 720 pixels - ie it could just resolve 720 alternate black and white lines. The reason that UK digital TV uses UHF channels which are 8 MHz apart is that analogue needed 6 MHz to transmit
*a single TV station* and a bit of extra bandwidth was allowed (hence 8 rather than 6 MHz spacing).
That's a good point about statistical multiplexing: it allocates a variable bit rate to each station in the mux according to what it needs to retain
good quality. The hope is that at times when BBC 1 needs a higher bit rate
to reproduce lots of detail and motion (which doesn't compress well), BBC 2, 3 and 4 might happen not to need as much. I imagine that during coverage of the Queen's death, lying-in-state and funeral, broadcasters had to take care not to exceed the total bandwidth of a mux (or hit its brickwall maximum bandwidth, affecting quality) at times when several channels in the mux were showing identical pictures, no the normal rules of statistical multiplexing didn't apply.
Yes I never quite understood Nicam which seemed to have a very short life cycle, coming as it did just before full digital. To be honest my mind
tells me that nicam sound actually sounded better than the current sound which seems to be plagued with leaden audio, which sounds like a wider
band version of some telephone codecs.
Yes I never quite understood Nicam which seemed to have a very short life cycle, coming as it did just before full digital. To be honest my mind
tells me that nicam sound actually sounded better than the current sound which seems to be plagued with leaden audio, which sounds like a wider
band version of some telephone codecs.
Brick wall filtering and lack of dynamics.
I often wondered what might happen to a multiplex if every channel put
out screens of totally random white noise on the video. I'd imagine it
would all go very blocky. These compression systems to get more channels
into less space are after all, a compromise.
Yes I never quite understood Nicam which seemed to have a very short life cycle, coming as it did just before full digital. To be honest my mind tells me that nicam sound actually sounded better than the current sound which seems to be plagued with leaden audio, which sounds like a wider band version of some telephone codecs.
On 30/10/2022 09:45, Brian Gaff wrote:
Yes I never quite understood Nicam which seemed to have a very short
life
cycle, coming as it did just before full digital. To be honest my
mind tells
me that nicam sound actually sounded better than the current sound which
seems to be plagued with leaden audio, which sounds like a wider band
version of some telephone codecs.
NICAM-728 was used for nearly twenty years I think and only ended with Digital Switch Over.
The first is how do the cameras create the colour
signal, ie is it completely digital from the ccd in the camera, then encoded in your format of choice, or did or do we have a system where the old fashioned are converted into the pixels etc later on.
Similarly at the
receiving end, since there appear to be no lines as such, is the actual screen merely created by the software that decompresses and scales the incoming signal once its been de multiplexed to the channel you want to look at.
Another issue that hasn't been mentioned is interlacing. This was
essential in the days of CRT TVs to reduce the perceived flicker without doubling the frame rate. Now that (almost) all TVs have LED screens,
where each pixel can be lit, simultaneously, for the full 1/25 of a
frame period, interlacing is irrelevant.
Do modern TV cameras actually scan the frame interlaced (ie all the odd rows >followed by all the even rows) or do they scan progressively (rows 1, 2, 3,
4 etc)? In other words, do you still get two fields that are exposed 1/50 >second apart, with movement between the fields, or are all the pixels
exposed simultaneously, with no movement between the odd and even fields?
I took courses in colour TV during the middle to late sixties. I
understood Walter Bruch's PAL system and our 625 line variant.
But I honestly never troubled to find out how our digital TV system
works.
Can someone point me to a sort of "UK Digital TV for geriatrics" that
might be helpful?
TIA, Alan
Yes I never quite understood Nicam which seemed to have a very short
life cycle, coming as it did just before full digital. To be honest my
mind tells me that nicam sound actually sounded better than the current
sound which seems to be plagued with leaden audio, which sounds like a
wider band version of some telephone codecs. Brick wall filtering and
lack of dynamics. I often wondered what might happen to a multiplex if
every channel put out screens of totally random white noise on the
video. I'd imagine it would all go very blocky. These compression
systems to get more channels into less space are after all, a
compromise. Brian
If you have the ability to record a DVB data stream to a PC file (eg
using NextPVR, TVHeadend or VLC and a DVB-USB tuner), and you are
really fascinated by the technicalities of DVB, I can recommend a free utility called TSReaderLite (Windows only). This is a cut-down version
of a version that costs money.
So called LED TVs are actually LED (as against cold cathode) backlit LCD ones.
"Woody" <harrogate3@ntlworld.com> wrote in message news:tjjqfd$3k5oe$1@dont-email.me...
On Sat 29/10/2022 18:54, pinnerite wrote:
I took courses in colour TV during the middle to late sixties.
I understood Walter Bruch's PAL system and our 625 line variant.
But I honestly never troubled to find out how our digital TV system
works.
Can someone point me to a sort of "UK Digital TV for geriatrics" that
might be helpful?
Google the usual best bet - DVB for Dummies? (DVB is the technical name
for UK DTTV.) If that spurs you on and you want to research HD then its
DVB-T2.
If you have the ability to record a DVB data stream to a PC file (eg using NextPVR, TVHeadend or VLC and a DVB-USB tuner), and you are really
fascinated by the technicalities of DVB, I can recommend a free utility called TSReaderLite (Windows only). This is a cut-down version of a
version that costs money.
It shows you all the various tables in the DVB stream which a TV uses when
it does its initial tune/scan and then saves the information to its local memory so when you ask for BBC1 the TV knows which frequency to tune to,
and the stream IDs for video, programme sound, audio description sound, subtitles. There's also TVCapture, made by the same company that makes NextPVR, which can record a 1-minute sample of any DVB multiplex - so you
get all the channels that are contained in the mux. VLC (Media | OPen
Capture Device, Capture mode=TV-digital, Transponder/mux frequency=482,000 (kHz) can tune to any mux (if you have a tuner) and can then record the
whole mux indefinitely. (Substitute one of your correct mux frequencies
where I've written 482,000).
One thing to be aware of: digital SD uses 720x576 because these numbers
are compatible with 625-line analogue TV, which had 575 lines of picture
(the rest was sync pulses) and the bandwidth gave a horizontal resolution (for an old 4:3 frame) of about 720 pixels - ie it could just resolve 720 alternate black and white lines. The reason that UK digital TV uses UHF channels which are 8 MHz apart is that analogue needed 6 MHz to transmit
*a single TV station* and a bit of extra bandwidth was allowed (hence 8 rather than 6 MHz spacing).
On 30/10/2022 09:25, Brian Gaff wrote:
The first is how do the cameras create the colour
signal, ie is it completely digital from the ccd in the camera, then
encoded
in your format of choice, or did or do we have a system where the old
fashioned are converted into the pixels etc later on.
You are confusing sampling with digital, and furthermore, you are
specifying a specific technology which is a sampled analogue one. CCD definitely reads out a sequence of analogue values that correspond to
pixels. I suppose the A/D convertor may be on the same chip, so the
analogue signal might not leave the chip.
I'm sure CMOS does the same, except that it is not physically constrained
to reading out lines sequentially.
Similarly at the receiving end, since there appear to be no lines as
such, is the actual screen merely created by the software that
decompresses and scales the incoming signal once its been de multiplexed
to the channel you want to look at.
There are lines on the screen, but there are negligible gaps between them,
so you need to get out a magnifying glass to see them. The images are
also rectangular arrays of pixels, so there are lines in the image as
well. A specialised IC will interpolate the images pixels to fit the
display ones, e.g. "scaler" in the diagram in this 2014 article: <https://www.electronicproducts.com/system-block-diagram-for-atsc-digital-tv/>.
"Brian Gaff" <brian1gaff@gmail.com> wrote in message news:tjlh2u$3a0s$1@dont-email.me...
Yes I never quite understood Nicam which seemed to have a very short life
cycle, coming as it did just before full digital. To be honest my mind
tells me that nicam sound actually sounded better than the current sound
which seems to be plagued with leaden audio, which sounds like a wider
band version of some telephone codecs.
Brick wall filtering and lack of dynamics.
I often wondered what might happen to a multiplex if every channel put
out screens of totally random white noise on the video. I'd imagine it
would all go very blocky. These compression systems to get more channels
into less space are after all, a compromise.
That's a good point about statistical multiplexing: it allocates a
variable bit rate to each station in the mux according to what it needs to retain good quality. The hope is that at times when BBC 1 needs a higher
bit rate to reproduce lots of detail and motion (which doesn't compress well), BBC 2, 3 and 4 might happen not to need as much. I imagine that
during coverage of the Queen's death, lying-in-state and funeral, broadcasters had to take care not to exceed the total bandwidth of a mux
(or hit its brickwall maximum bandwidth, affecting quality) at times when several channels in the mux were showing identical pictures, no the normal rules of statistical multiplexing didn't apply.
On 30/10/2022 10:26, NY wrote:
That's a good point about statistical multiplexing: it allocates a
variable
bit rate to each station in the mux according to what it needs to retain
good quality. The hope is that at times when BBC 1 needs a higher bit
rate
to reproduce lots of detail and motion (which doesn't compress well), BBC
2,
3 and 4 might happen not to need as much. I imagine that during coverage
of
the Queen's death, lying-in-state and funeral, broadcasters had to take
care
not to exceed the total bandwidth of a mux (or hit its brickwall maximum
bandwidth, affecting quality) at times when several channels in the mux
were
showing identical pictures, no the normal rules of statistical
multiplexing
didn't apply.
Wasn't there potentially a similarly problem in analogue days when all the Senders at the big Short Wave sites were transmitting the Queen's Speech
at the same time. It would have played havoc with the National Grid if
all exactly synchronised so they added small delays so not synchronised.
Not only that but the of stages of tuners were and maybe still are affected by the adjacent channel being strong, either desensing the set or intermodulation effects in the rf stages. Obviously they tried not to use Adjacent channels, but often you could get another region almost as strongly as yours. Brian
On 30/10/2022 09:45, Brian Gaff wrote:
Yes I never quite understood Nicam which seemed to have a very short life
cycle, coming as it did just before full digital. To be honest my mind
tells
me that nicam sound actually sounded better than the current sound which
seems to be plagued with leaden audio, which sounds like a wider band
version of some telephone codecs.
NICAM-728 was used for nearly twenty years I think and only ended with Digital Switch Over.
NICAM was used internally by the Beeb from the early 80s (it replaced
the linear PCM streams on their national radio distribution)
In article <20221029185426.f45b47e35be4196c0e590d50@gmail.com>,
pinnerite
<pinnerite@gmail.com> wrote:
I took courses in colour TV during the middle to late sixties. I
understood Walter Bruch's PAL system and our 625 line variant.
But I honestly never troubled to find out how our digital TV system
works.
Can someone point me to a sort of "UK Digital TV for geriatrics" that
might be helpful?
TIA, Alan
Try books by John Watkinson.
Jim
--
Please use the address on the audiomisc page if you wish to email me. Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html
Caldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused?
David Woolley wrote:
So called LED TVs are actually LED (as against cold cathode) backlit LCD ones.Apart from OLED TVs.
Apart from OLED TVs.
On Monday, 31 October 2022 at 09:57:33 UTC, Mark Carver wrote:
Caldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused?
Well, its seemed a pretty short time at the time. I actually only ever had one set like that as it seemed most mono tvs still used the intercarrier fm sound originally developed. Brian
On 31/10/2022 09:43, Brian Gaff wrote:
Not only that but the of stages of tuners were and maybe still areAdjacent channel working is a perquisite for DVB-T, it had to be, in
affected
by the adjacent channel being strong, either desensing the set or
intermodulation effects in the rf stages. Obviously they tried not to use
Adjacent channels, but often you could get another region almost as
strongly
as yours. Brian
order to accommodate six or more muxes per transmitter, in a broadcast
band that now only runs from Ch 21 to 48
Caldbeck has 8 muxes all in a block from 21-28
On Mon, 31 Oct 2022 08:22:37 -0700 (PDT), "wrights...@aol.com" <wrights...@f2s.com> wrote:
On Monday, 31 October 2022 at 09:57:33 UTC, Mark Carver wrote:
Surely you mean photns. Traveling at speed of light they areCaldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused?
everywhere all the time.
On 31/10/2022 09:57, Mark Carver wrote:
On 31/10/2022 09:43, Brian Gaff wrote:
Not only that but the of stages of tuners were and maybe still areAdjacent channel working is a perquisite for DVB-T, it had to be, in
affected
by the adjacent channel being strong, either desensing the set or
intermodulation effects in the rf stages. Obviously they tried not
to use
Adjacent channels, but often you could get another region almost as
strongly
as yours. Brian
order to accommodate six or more muxes per transmitter, in a
broadcast band that now only runs from Ch 21 to 48
Caldbeck has 8 muxes all in a block from 21-28
Was a spacing of three UHF channels (eg 60 and 63) the smallest that
was used between two stations on same transmitter in analogue days, or
did some transmitters use a spacing of two (eg 60 and 62).
Could the tuners on analogue TVs that we made around the time of DSO
have tolerated adjacent UHF channels? Or were even "modern" tuners
unable to reject adjacent-channel signals.
How good is digital at rejecting a weaker signal from a distant
transmitter than happens to be on the same channel as a stronger
signal from the normal transmitter? Is it co-channel interference that
tends to cause an increase in glitches at times of abnormal
propagation, or are glitches normally due to some muxes being weaker
than normal and therefore having poorer SNR? (I'm distinguishing
between random noise and weak but discernable digital signal).
There was a noticeable difference in sound quality between FM and NICAM
- and that's ignoring the rather obvious difference between mono and
stereo.
On 31/10/2022 09:57, Mark Carver wrote:
On 31/10/2022 09:43, Brian Gaff wrote:
Not only that but the of stages of tuners were and maybe still areAdjacent channel working is a perquisite for DVB-T, it had to be, in
affected
by the adjacent channel being strong, either desensing the set or
intermodulation effects in the rf stages. Obviously they tried not to use >> Adjacent channels, but often you could get another region almost as
strongly
as yours. Brian
order to accommodate six or more muxes per transmitter, in a broadcast
band that now only runs from Ch 21 to 48
Caldbeck has 8 muxes all in a block from 21-28Was a spacing of three UHF channels (eg 60 and 63) the smallest that was
used between two stations on same transmitter in analogue days, or did
some transmitters use a spacing of two (eg 60 and 62).
Could the tuners on analogue TVs that we made around the time of DSO
have tolerated adjacent UHF channels? Or were even "modern" tuners
unable to reject adjacent-channel signals.
Nowadays, as you say, some digital muxes are on adjacent channels, and
no-one bats an eyelid at that.
How good is digital at rejecting a weaker signal from a distant
transmitter than happens to be on the same channel as a stronger signal
from the normal transmitter? Is it co-channel interference that tends to cause an increase in glitches at times of abnormal propagation, or are glitches normally due to some muxes being weaker than normal and
therefore having poorer SNR? (I'm distinguishing between random noise
and weak but discernable digital signal).
On Monday, 31 October 2022 at 23:59:36 UTC, BrightsideS9 wrote:
On Mon, 31 Oct 2022 08:22:37 -0700 (PDT), "wrights...@aol.com" <wrights...@f2s.com> wrote:
On Monday, 31 October 2022 at 09:57:33 UTC, Mark Carver wrote:
No I meant the electrons in the coax. All that jiggling about, yet when you press your ear against an aerial downlead you can't hear a thing.Surely you mean photns. Traveling at speed of light they areCaldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused?
everywhere all the time.
Bill
The Luma (black and white) signal on PAL was AMThe chroma was also a derivative of AM.
Indeed on satellite the channels overlap, but alternate ones are polarised horizontal and vertical and on adjacent satellite the pattern is reversed.
Ears are not electromagnetic.
I imagine the "duplicate" frequencies are actually very slightly
different, but evidently much more similar than normal.
"R. Mark Clayton" <notyalckram@gmail.com> wrote in message news:88abee71-93c9-4ec9-af9d-2ba74cf95246n@googlegroups.com...
Indeed on satellite the channels overlap, but alternate ones are
polarised horizontal and vertical and on adjacent satellite the
pattern is reversed.
I've always wondered how a few satellite muxes (eg 11306 H/V) are on the
same frequency and distinguished only by polarisation, when most
transponders are separated both by frequency and polarisation. I imagine
the "duplicate" frequencies are actually very slightly different, but evidently much more similar than normal.
Surely you mean photns. Traveling at speed of light they are everywhere
all the time.
On Monday, 31 October 2022 at 09:57:33 UTC, Mark Carver wrote:
Caldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused? Bill
On 01/11/2022 12:39, NY wrote:If you're talking about signals from adjacent satellites, yes it can be a problem. Sometimes it explains why some muxes are poor when others are good. Better dish alignment or a bigger dish is usually the answer.
I imagine the "duplicate" frequencies are actually very slightlyI don't think enough spectrum is spare between channels for that. I
different, but evidently much more similar than normal.
think it is simply a matter that the receiving dish has to be more
accurately aligned, to reject the other polarisation.
Ears aren't hydraulic but I can hear the water in a pipe.No I meant the electrons in the coax. All that jiggling about, yet when you press your ear against an aerial downlead you can't hear a thing.Ears are not electromagnetic.
Bill
Ears aren't hydraulic but I can hear the water in a pipe.
Bill
On Monday, 31 October 2022 at 09:57:33 UTC, Mark Carver wrote:
Caldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused?
On Mon, 31 Oct 2022 08:22:37 -0700 (PDT), wrights...@aol.com <wrights...@f2s.com> wrote:That probably explains it.
On Monday, 31 October 2022 at 09:57:33 UTC, Mark Carver wrote:
No, they don't care. They've got a negative attitude to everything.Caldbeck has 8 muxes all in a block from 21-28I still can't figure how the electrons know what they're supposed to be doing. Don't they get confused?
On Tuesday, 1 November 2022 at 12:13:59 UTC, R. Mark Clayton wrote:
Ears aren't hydraulic but I can hear the water in a pipe.No I meant the electrons in the coax. All that jiggling about, yet when you press your ear against an aerial downlead you can't hear a thing.Ears are not electromagnetic.
Bill
Bill
On 01/11/2022 12:13, R. Mark Clayton wrote:
Ears are not electromagnetic.
I could "hear" the VLF pulses from the OMEGA transmitter at Criggion
when we visited (many years ago) and went in the coil chamber.
On Tuesday, 1 November 2022 at 12:13:59 UTC, R. Mark Clayton wrote:
Ears aren't hydraulic but I can hear the water in a pipe.No I meant the electrons in the coax. All that jiggling about, yet when you press your ear against an aerial downlead you can't hear a thing.Ears are not electromagnetic.
Bill
Bill
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