Interlaced Video

[Sci-Fi-Fan]

Can any of you guru's out there explain to me why a Tv Network here in the United Kingdom is still using Interlaced Video in 2017?

As far as I understand it, interlacing was used decades ago to double horizontal resolutions for ancient crt tvs that could only display 256 horizontal scan lines.

But with modern HD and 4K progressive digital displays that limitation has long since gone the way of the dinosaur.

So I just cannot fathom why a studio is still using such an obsolete technology in our modern digital world..

Can any makes sense of this?

[Katie Boundary]

Can any of you guru's out there explain to me why a Tv Network here in the United Kingdom is still using Interlaced Video in 2017?

Because whatever program they're showing was originally made that way and deinterlacing it would be more trouble than it's worth?

As far as I understand it, interlacing was used decades ago to double horizontal resolutions for ancient crt tvs that could only display 256 horizontal scan lines.

Then you understand incorrectly. NTSC sets like the ones used in the USA and UK have 480 scanlines, and nothing about CRT technology inherently prevented us from making a TV standard with 100,000,000 scanlines or any other number we wanted. The real reason for interlacing was to maximize the screen refresh rate without increasing bandwidth usage.

[hello_hello]

My understanding is interlacing is also a way to squeeze more out the available bandwidth.

It's true that very early CRTs could only scan a limited number of lines per second (as opposed to displaying them) so for interlaced video they'd refresh every even line, then every odd line, which also helped reduce flicker and increase the smoothness of motion. At 50Hz the limit was originally a little over 200 scan lines per 1/50th second, so the UK system began as 405 line system and later increased to 625 line as technology improved. I don't know when the UK switched but I'm pretty sure the very early episodes of Doctor Who were 405 line.

I'd imagine the motivation for interlacing today would still be bandwidth/compression related, but 1080i has a higher temporal resolution than 720p at the same frame rate, so I assume it'd be more likely to be used for sporting events where there's lots of motion, or maybe broadcasters think 1080i sounds more impressive than 720p, although I'd prefer the latter most of the time.

In Australia the switch from mpeg2 to mpeg4 has been slow because many early HD TVs and set top boxes can't decoded mpeg4. I watch almost no free-to air TV, but I think some broadcasters are using mpeg4 for some non-primary channels these days, while the rest is still overly-compressed mpeg2 crap. The latest "Freeview certified" devices only have to support 576p, 720p and 1080i, although mpeg4 is mandatory. We might have 4k TVs but I can't see free-to air broadcasts being 4k for a long time. I don't know what the situation is in the UK.

[hello_hello]

Then you understand incorrectly. NTSC sets like the ones used in the USA and UK have 480 scanlines, and nothing about CRT technology inherently prevented us from making a TV standard with 100,000,000 scanlines or any other number we wanted. The real reason for interlacing was to maximize the screen refresh rate without increasing bandwidth usage.

Not true. Aside from the fact the UK used PAL sets, not NTSC, a CRT picture is "drawn" one line at a time by an electron beam and there were lots of limitations to overcome, hence the original UK system only being 405 line.
https://en.wikipedia.org/wiki/Interlaced_video#History

Edit: Or depending how far back you go, as I discovered here (https://en.wikipedia.org/wiki/John_Logie_Baird), the BBC briefly broadcast using a 240 line progressive system and even a 30 line system before that.

[Sci-Fi-Fan]

Thank you hello_hello

Ok from a broadcast / bandwidth pov it has some merits, but on a brand new Blu-Ray filmed in 2016, broadcast and released in 2017, surely it would be filmed and mastered in 1080p.
Then again doctor who didn't move from standard definition to HD until. 2010.

Interlacing may use less bandwidth, but imo the loss of quality is not worth the compromise.

[kolak]

Can any of you guru's out there explain to me why a Tv Network here in the United Kingdom is still using Interlaced Video in 2017?

As far as I understand it, interlacing was used decades ago to double horizontal resolutions for ancient crt tvs that could only display 256 horizontal scan lines.

But with modern HD and 4K progressive digital displays that limitation has long since gone the way of the dinosaur.

So I just cannot fathom why a studio is still using such an obsolete technology in our modern digital world..

Can any makes sense of this?

Because they have tons of equipment which supports only 50i and they not going to invest millions to replace it. TV is so legacy :)
Movies are actually transmitted in progressive mode ( at least on some channels), so it's not true that everything is shown as interlaced. It will also depend on original nature of the content. There is still plenty interlaced shot content. Next step would be to move to 50p (not 25p as this is problematic) which requires quite a big hardware changes. They just not willing to invest, that's why you have Netflix etc which was first to stream 4K/HDR etc. Technology is changing fast and broadcast is very slow to adapt as it require a lot of investment.

[poisondeathray]

Ok from a broadcast / bandwidth pov it has some merits, but on a brand new Blu-Ray filmed in 2016, broadcast and released in 2017, surely it would be filmed and mastered in 1080p.
Then again doctor who didn't move from standard definition to HD until. 2010.


ok, but was it a "film", actually filmed ? A theatrical piece ?

Or was it "video", like you originally stated ?

Because one common reason is BD doesn't support 1080p50 or 1080p60 , so if you need the temporal resolution, they are released as "i" . Although 720p50 / 720p60 are valid for BD , marketing says "1080" "sounds" better than "720"

And if it's a 24p theatrical film conversion to "25p" , the actual content most likely is 25p, not interlaced .

[kolak]

Movies are actually transmitted as progressive (at least this is what my TV is telling me), so no problem here.

[hello_hello]

Thank you hello_hello

Ok from a broadcast / bandwidth pov it has some merits, but on a brand new Blu-Ray filmed in 2016, broadcast and released in 2017, surely it would be filmed and mastered in 1080p.

I'd agree, but according to this it's not a UK phenomenon. 1080i is a world-wide thing for free to air TV.
https://en.wikipedia.org/wiki/1080i#Broadcast_standard
Worldwide, most HD channels on satellite and cable broadcast in 1080i. In the United States, 1080i is the preferred format for most broadcasters, with Discovery Communications, Viacom, Time Warner, Comcast owned networks broadcasting in the format; along with most smaller broadcasters. Only 21st Century Fox-owned television networks and Disney-owned television networks, along with MLB Network and a few other cable networks use 720p as the preferred format for their networks; A+E Networks channels converted from 720p to 1080i sometime in 2013 due to acquired networks already transmitting in the 1080i format.

Would it necessarily be a bad thing if the content is progressive though, because the Progressive segmented frame (https://en.wikipedia.org/wiki/Progressive_segmented_frame) system allows progressive video to be treated as interlaced, and I assume the fields only need to be recombined again for a progressive frame. If it's broadcast that way though, I don't know what happens at the TV end.... whether the fields are just combined rather than de-interlaced.... or if there's a way to distinguish it from real interlaced video, or if a TV would de-interlace blindly or only when combing is detected etc. I assume the chroma sub-sampling is the same as for interlaced but I've not really thought about any of that before. Someone else will probably know more, but in a perfect world PsF would be distinguishable from interlaced (EDIT: going by what kolak has said, it appears that's the case).

Then again doctor who didn't move from standard definition to HD until. 2010.

I'm not sure if it's changed, but 576p (as opposed to 576i) was/is considered to be HD, at least in respect to government regulations in Australia. I kind of remember 576p being pretty common and being pretty peeved about it. For all I know, it still is.

[Sci-Fi-Fan]

ok poisondeathray has hit the nail on the head. the uk pal standard of 25 fps is not blu-ray compliant at 1080p resolution, so as to be encoded as interlaced, or in the case of the blu-ray i'm referring to which is encoded as MBAFF.
so in all likely hood it is filmed as progressive but encoded as interlaced / MBAFF to be compliant with the blu-ray spec.

I Guess when they created the blu-ray spec they didn't take the PAL 25fps standard into consideration :/

Kolak also makes a very valid point about the cost of upgrading / replacing outdated equipment.

[kolak]

Problem is that some older broadcast equipment doesn't even support PsF as this was introduce bit later than original interlaced specs.

This is probably how movies are transmitted- as PsF when they start at transmission room. At consumer end (on TVs decoders) this is treated as progressive and it's indistinguishable from "real" progressive.

[hello_hello]

ok poisondeathray has hit the nail on the head. the uk pal standard of 25 fps is not blu-ray compliant at 1080p resolution, so as to be encoded as interlaced, or in the case of the blu-ray i'm referring to which is encoded as MBAFF.
so in all likely hood it is filmed as progressive but encoded as interlaced / MBAFF to be compliant with the blu-ray spec.

According to the info here (http://www.x264bluray.com/home/1080i-p) for Bluray compatibility 1080p25 has to be encoded with x264 using it's "fake interlaced" option, which I've never really understood completely.
The info here (http://www.chaneru.com/Roku/HLS/X264_Settings.htm#fake-interlaced) says it simply marks a progressive stream as interlaced, but given interlaced and progressive video are different in respect to chroma subsampling, I don't understand how that effects (or not) the way it'd be decoded.

[kolak]

It's just treating 25p as interlaced, but with no offset between fields in time. Because there is no offset in time between them they can be perfectly put back into whole frame.
At the end you get the same picture (progressive). It's just a "hack" as 25p has been not included in BD spec for whatever reason!

[hello_hello]

How does the decoder know it's fake interlaced though, as opposed to the real thing, and how would the player/TV know not to de-interlace it but treat is as progressive?

The same questions in relation to chroma subsampling. The way I understand it the chroma for each field is subsampled individually for interlaced video, given each field is a different moment in time, but how would the decoder know the "fake interlaced" video has progressive chroma subsampling rather than interlaced chroma subsampling? I'm thinking it should matter, but maybe not??

I assume for PsF, how it's done is part of the specification (although I can't find definitive information on how PsF's chroma-subsampling works) but "fake interlaced" seems like it'd be a different story.

[sneaker_ger]

x264 "fake interlaced" is PAFF. In the bitstream there are flags to show the decoder which frames are progressive and which are made of two fields. This is allowed. And then x264 simply doesn't mark any frame as interlaced.

[kolak]

Which should translate to perfect progressive decode.
PsF is related to SDI and handling it is defined by strict SDI spec. PsF doesn't really exist outside SDI world. PsF SDI signal by many video cards is translated to progressive HDMI signal (sometimes to interlaced).
It's all legacy.

[Katie Boundary]

Sorry, I just checked and the UK uses PAL, not NTSC. I could have sworn that I once saw a standards map that showed the UK as NTSC.

I stand by everything else that I said.

[hello_hello]

I stand by everything else that I said.

Well if you're going to be wrong, why not be proud of it? :)

[hello_hello]

x264 "fake interlaced" is PAFF. In the bitstream there are flags to show the decoder which frames are progressive and which are made of two fields. This is allowed. And then x264 simply doesn't mark any frame as interlaced.

Ahh..... that makes sense.

Cheers.

[StainlessS]

PAL

Afghanistan
Algeria
Argentina (N)
Austria
Australia
Bangladesh
Belgium
Brazil (M)
China
Denmark
Finland
Germany
Hong Kong
Iceland
India
Indonesia
Iraq
Ireland
Israel
Italy
Jordan
Kenya
Kuwait
Liberia
Malaysia
Netherlands
Nigeria
Norway
New Guinea
Pakistan
Singapore
South Africa
South W. Africa
Sudan
Sweden
Switzerland
Thailand
Turkey
Uganda
United Kingdom
United Arab Emirates
Yugoslavia
Zambia


NTSC

Canada
Chile
Costa Rica
Cuba
Dominican Republic
Ecuador
Japan
Mexico
Nicaragua
Panama
Peru
Philippines
Puerto Rico
South Korea
Taiwan
U.S.A.


NTSC, Rumoured to stand for Never Twice the Same Colour.

[Groucho2004]

nothing about CRT technology inherently prevented us from making a TV standard with 100,000,000 scanlines or any other number we wanted.I don't expect you to understand anything about electronics or manufacturing limits of cathode ray tubes but even common sense should be sufficient to realize the nonsense you're uttering.

[johnmeyer]

Original analog TV (NTSC, PAL, SECAM) was interlaced to provide more fluid motion within the constraints of the bandwidth allocated to each over the air channel (which was the only way most people could view video at home until the late 1970s). When home video recording equipment became available, that constraint actually got worse, because the "engineering tradeoffs" between cost and usability reduced that analog bandwidth even more. This was true regardless of the system: Beta, VHS, 8mm all had similar constraints.

So when TV went from analog to digital, why was interlacing still used, and in fact, used a LOT?

Same problem: engineering constraints. For those not familiar with that term, the more common way to say it is that you can't put ten pounds of stuff in a five pound bag.

The OTA frequency allocation is precisely what it was back in 1948. Digital did not change the laws of physics, and more frequency allocation is out of the question because the electromagnetic spectrum has a finite energy spectrum available for broadcasting.

Even when it comes to delivery by streaming, Blu-Ray, etc., similar constraints come into play. For instance, computer speeds stalled out over a decade ago, and we are not likely to see any faster CPUs for a long time. We are way down the learning curve on video compression (I was very much involved with this back in the early 1990s) and you aren't going to be able to get high quality video into smaller containers. While many systems can satisfactorily play 60 fps progressive material, not all satellite and cable channels can carry it.

The OP seems to think that we can just keep adding resolution and go to higher framerates, but in fact, with the technology we have today and the infrastructure that is in place to carry digital video and audio, even 4K is barely making it to most screens. There is no OTA 4K, and DirecTV and cable has almost no live 4K. Most 4K programming is a download then watch affair.

Finally, true interlacing, where the alternate lines are displayed 1/60 (or 1/50) of a second apart, actually works extraordinarily well and looks just fine. It is only when the display can't handle interlacing natively and only when the deinterlacing is botched that we have a problem. Most deinterlacing built into modern displays works amazingly well: I am very critical and have not once watched my 5-year-old LCD big screen and thought, "wow, I can see deinterlacing artifacts."

So, deinterlacing lets you get the fluidity of 50 or 60 events per second, but at 1/2 the bandwidth (more or less) that would be require to get 50 or 60 complete frames per second.

[Katie Boundary]

I don't expect you to understand anything about electronics or manufacturing limits of cathode ray tubes but even common sense should be sufficient to realize the nonsense you're uttering.

Keep in mind that I'm talking about what's physically possible, not what would be practical.

[StainlessS]

Keep in mind that I'm talking about what's physically possible, not what would be practical.

Tut, tut, not physically possible (this century), nor practical.

EDIT: I seem to recall that sample(pixel) signal for PAL TV was something like 30MHz, so if new system has 100,000,000 scanlines
then might be about vertically (100,000,000 / ~625) 160,000 times greater, and making assumption that display is about 160,000 times
wider, then 160,000 * 160,000 = 2.56 *10^10 * 30MHz = 7.68 * 10^17 = 7,680,000,000,000,000,000 Hz.

Anybody know at what frequency X-Rays start ? (C/Wavelength, 300,000,000/Wavelength of XRAY)

XRays start at about 10 nano meters, so, 300,000,000/1.0*10^-8 = 30,000,000,000,000,000 Hz

So, would be well into XRays, or maybe even beyond that, (whats above XRAYS ?)

Numbers above are probably riddled with errors, but probably not that ridiculous.

Me guessin' not possible even beyond this century. (unless you watch from behind 6 inches of leaded glass).

EDIT: My brother is an X-RAY engineer, maybe I ask him (specializing in TV, ie monitors in MRI scanners etc)

[hello_hello]

Keep in mind that I'm talking about what's physically possible, not what would be practical.

Keep in mind I provided a link where it was explained how the physical limitations of early CRT technology limited the number of scan lines used but you've chosen to ignore it.

Even if your distinction was accurate, which it isn't, in the real world what's possible is usually limited to what's practical so they often amount to much the same thing.

[johnmeyer]

... nothing about CRT technology inherently prevented us from making a TV standard with 100,000,000 scanlines or any other number we wanted. The real reason for interlacing was to maximize the screen refresh rate without increasing bandwidth usage.The second sentence is absolutely true. The first sentence is wrong. StainlessS' response to this obviously incorrect assertion addresses one reason why 100,000 scan lines cannot be done. You also have to dramatically increase the voltages used to deflect the electron beam. As many of the older people in these forums will remember, when the first large color TVs started to appear in the mid-1960s, there was quite a bit of concern about the level of X-rays they emitted. This happened because of the high voltages needed to drive only 525 lines at 60 fields per second:

Ionizing radiation in CRTs (https://en.wikipedia.org/wiki/Cathode_ray_tube#Ionizing_radiation)

If you build a circuit to drive the scanning lines faster, the x-ray level will increase dramatically. I can't even begin to calculate how much power would be required. If any of you have ever driven by one of the big nuclear accelerators, like SLAC at Stanford or the big cyclotron outside of Chicago, you get some idea of how much energy it takes to deflect particles (electrons in this case).

You also have to build an electronic circuit capable of scanning that many lines in a fraction of a second. The quote Scotty from Star Trek: " We can't even do that in the twenty-third century."

[hello_hello]

A bit of trivia (at least for me).

Where I am, the ABC (Australian equivalent of the BBC) have used the same logo (or variations of it) since the 1960s. Until now I'd been completely oblivious as to it's origins. I stumbled on this while reading other broadcast related pages. You can learn something every day.....

https://en.wikipedia.org/wiki/Australian_Broadcasting_Corporation#Lissajous_curve_logo
https://en.wikipedia.org/wiki/Lissajous_curve

[Groucho2004]

whats above XRAYS ?gamma radiation. The TV will cause hair loss.

[StainlessS]

gamma radiation. The TV will cause hair loss.

Arh well, no change there then. :)

[Sci-Fi-Fan]

Thank you all for a very informative discussion.

In my op I was specifically referring to Blu-ray technology which was designed / Intended for High Definition Video Content, And have been recently frustrated to find that 2 Blu-Ray boxsets of Tv Shows (I recently brought) produced for
The BBC in the UK contained some older seasons that are clearly upscaled ports of the standard definition DVD versions of the series while the latest seasons are in full HD 1080i/p.

Now HD Capable displays have been around for a good decade now, so I wanted to understand why some tv networks are lagging so far behind in production / filming technology at least for Blu-ray.

As far as ota broadcasting goes, HD content can always be down scaled to fit into broadcasting limitations, but as has been pointed out, the cost of upgrading / replacing legacy equipment for smaller tv networks is prohibitive.

[wonkey_monkey]

Can any of you guru's out there explain to me why a Tv Network here in the United Kingdom is still using Interlaced Video in 2017?

Everyone's still using it. It was, and still is, a very quick and very efficient way to reduce bandwidth. Just chuck out half the lines and let the human brain - or a deinterlacer - fill in the gaps.

Arguably the need for a deinterlacer is onerous, but they were needed and made, and they are quite good these days. When the UK started shifting to digital broadcasts, everyone still had CRTs would require interlaced signals, so no point changing things then. As flat screen TVs came out, they needed to support interlacing. HD specs are old, so interlacing was still part of it, and it's supported by new TVs anyway so there was no good reason to stop using it.

I Guess when they created the blu-ray spec they didn't take the PAL 25fps standard into consideration :/

They did take into consideration. They realised it wasn't necessarily, because it can be perfectly (well, almost perfectly; not so you'd ever see the difference) encapsulated in 1080i50, which is part of the spec. This same encapsulation doesn't work between 1080p24 and 1080i60, so they are both in the spec.

And have been recently frustrated to find that 2 Blu-Ray boxsets of Tv Shows (I recently brought) produced for The BBC in the UK contained some older seasons that are clearly upscaled ports of the standard definition DVD versions of the series while the latest seasons are in full HD 1080i/p.

If it's Doctor Who, then the older seasons were only shot in SD. They're not upscales of the DVDs, but upscales of the SD master tapes.

The BBC had only just started experimenting with HD when Doctor Who restarted. They shot Torchwood in HD partly as an experiment, and as a result some of the first season episodes are a dark blurry mess because they didn't know exactly what they were doing. Effects for Doctor Who would also have been prohibitively expensive in HD back then - Torchwood's were more limited.

[hello_hello]

If it's Doctor Who, then the older seasons were only shot in SD. They're not upscales of the DVDs, but upscales of the SD master tapes.

My perception of time must be pretty bad. I would have assumed the BBC had been shooting everything in HD before the new series of Doctor Who (which is dead to me now) started.
Obviously not. Seems the first four season were SD. Do they put disclaimers on the Bluray packaging?

After reading your post I consulted Google and did some more reading:

https://en.wikipedia.org/wiki/List_of_Doctor_Who_home_video_releases#Blu-ray
The 1996 telemovie received a Blu-ray release on September 19, 2016. Curiously, despite being shot entirely on film, the Blu-ray release is simply an HD upscale of the 480p broadcast copy

How pissed would you be if you'd paid good money for that?

[sneaker_ger]

Everyone's still using it.
There are channels that use 720p50 or 1080p50. On DVB-T2 in Germany I think not a single channel uses interlacing. HEVC interlacing is inefficient.
If you look through some older posts on this forum you may also find such result with x264. You still save bandwidth in the encoding chain and power on encode/decode but in terms of DVB bandwidth interlacing is not good anymore.
Think about it: throwing away lines is a very stupid way of compression (as is chroma sub-sampling). It shouldn't be surprising for AVC, HEVC or other modern lossy compression schemes to surpass it.

[SeeMoreDigital]

Too bad that the french 819-line system (https://en.wikipedia.org/wiki/Analog_high-definition_television_system#French_819-line_system) never took off in the analogue TV world ;)

[Sci-Fi-Fan]

How pissed would you be if you'd paid good money for that?

I payed over £100 to import "Merlin Complete Series Blu-Ray" from Amazon.com (as it was not availlable in UK) only to find that the first 3 Seasons are SD upscales of questionable quality.

So yeah I was pissed.

And no they don't tell you in the pakaging or description that they are upscales.

[kolak]

Yep- common practice, specially these days when they expect you to do Blu-ray almost for "free". They use any existing master even if it was done ages ago and it's not good enough to use as Blu-ray source.
No one cares anymore, all what counts is sell numbers.
Spoken with my friend who is in BD/UHD BD industry and UHD is doing terribly bad. After initial not bad start now almost no one (except few big places in the whole world) doing UHD projects. When he told me what studios offer for authoring UHD+BD+DVD I'm not surprised- it just doesn't make sense from authoring facility business point. Now it's all in hands of big places which are factories- only numbers count, so don't expect any attention to details or polished transfers. 10 years ago there were many smaller authoring houses in London, today there is none.
My old company left BD+DVD business few year ago and even then it was already barely profitable.
Shame as Netflix with its sub 20Mbit UHD encodes is far from delivering high-end quality experience at home.

[Sharc]

..... It's just a "hack" as 25p has been not included in BD spec for whatever reason!
It is included in the specs as 720x576 25p (or 25i), Level 3.2, for Secondary Video.

[kolak]

We are talking about HD.
Yes, you can have 576 25p as secondary video, so why not have HD 25p as primary in the spec?
Decoding power needed for 25p compared to 24p is about the same.

[wonkey_monkey]

It is included in the specs as 720x576 25p (or 25i), Level 3.2, for Secondary Video.

But are they separate, or is 25p available simply as a by-product of 50i, as it is at HD resolution?

so why not have HD 25p as primary in the spec?

There's no need for it. 1920x1080x50i covers it.

[poisondeathray]

There's no need for it. 1920x1080x50i covers it.



"Covered", but not as "ideal" as native progressive .

1) Progressive > MBAFF > PAFF in terms of encoding efficiency or quality at a given bitrate .

2) It's not really an issue with BD playback, and even less so with "50Hz" area equipment, but there is potential for deinterlacing progressive content depending on the playback setup. It's been known to happen with "29.97p" encoded as fields with software (MBAFF or PAFF triggers deinterlace instead of content based detection for weave or 2:2 pulldown removal)

[Katie Boundary]

I seem to recall that sample(pixel) signal for PAL TV was something like 30MHz,

What the hell does that have to do with anything? I never said "100,000,000 scanlines @ 30 million samples per second", did I? Did I say anything about the refresh rate, or pixels per scanline?

(unless you watch from behind 6 inches of leaded glass).

I can't even begin to calculate how much power would be required. If any of you have ever driven by one of the big nuclear accelerators, like SLAC at Stanford or the big cyclotron outside of Chicago, you get some idea of how much energy it takes to deflect particles (electrons in this case).

Again, the whole "possible" versus "practical" distinction.

You also have to build an electronic circuit capable of scanning that many lines in a fraction of a second.

The error in your statement has been indicated in bold.

gamma radiation. The TV will cause hair loss.

It could also turn you into The Incredible Hulk.

[StainlessS]

@ Katie,

You excel yourself. [EDIT: although 30MHz was probably a little bit high, maybe knock off up to one '0' from the given numbers]

[johnmeyer]

She isn't even making any sense. Her last reply where she boldfaced my statement (where I said that you have to draw scanlines in a fraction of a second), claiming that was "the error in your statement" is either stupid, intentional trolling, or the product of some drug that I haven't had the pleasure to have experienced.

So she isn't even being a decent troll anymore because that dubious occupation at least requires making statements that make enough sense that they can get people riled up. I am totally baffled by the posts she's made the last few days.

[StainlessS]

Perhaps Katie would like to expand upon what it is that she thinks is possible, if not practical. (it would make it unnecessary to guess what it is that she means).

[johnmeyer]

Perhaps Katie would like to expand upon what it is that she thinks is possible, if not practical. (it would make it unnecessary to guess what it is that she means).
Maybe she's training to be a mystic, you know, those people who can say things that you can't quite figure out, and don't exactly make sense. You are then challenged to decide whether the person is simply nuts, or whether they have a much deeper understanding of the universe than any of us mere mortals could possibly comprehend.
"Mysticism and exaggeration go together. A mystic must not fear ridicule if he is to push all the way to the limits of humility or the limits of delight." -- Milan Kundera

Clearly no fear of ridicule in this instance.

[Katie Boundary]

Okay then...

1) What is the exact maximum number of scanlines that a functioning CRT can have?

2) Are CRTs with one scanline more than this number just impossible to make, or can they be made but they just won't function?

3) Why is it exactly this number?

[Sharc]

Okay then...

1) What is the exact maximum number of scanlines that a functioning CRT can have?
Infinite minus one

2) Are CRTs with one scanline more than this number just impossible to make, or can they be made but they just won't function?

Both, because of 1) which is the maximum
3) Why is it exactly this number?
Physical / technological constraints and cost.

[SeeMoreDigital]

Back in the 'olden days' when everything was still being broadcast in analogue and digital was in its infancy, Sony had some gear which supported 1125 lines. And Barco had some very good CRT monitors too.

There was even HD laserdisc :)

[StainlessS]

Okay then...

1) What is the exact maximum number of scanlines that a functioning CRT can have?

2) Are CRTs with one scanline more than this number just impossible to make, or can they be made but they just won't function?

3) Why is it exactly this number?

You say nothing about pixel width nor framerate nor physical sizes, and so nobody could attempt to answer your question.

It would all involve frequencies and amount of power required for scan coil deflections, and power applied to the electron beam fired at phosphor dots on CRT face, which must be powerful enough [EDIT: at pixel/dot frequency] to to excite the phosphor dots long enough to achieve the persistence required for for required framerate.
EDIT: Even if you had unlimited power, you would be limited by physical limits of materials, eg phosphor dots would have to be capable of not bursting into flame or turning into some kind of plasma.

So I would say that your question 1) amounts to "How long is a piece of string ?".

EDIT: You could only really ask if a particular spec CRT could be made, not what is max scanlines, as it all is inter dependent upon other parts of spec.
Even if you could more fully spec your requirements, eg giving FPS, frame aspect ratio and DPI (and eg fixed physical size, or physical size varying with number of scanlines), I doubt if anyone on the D9 could answer it.

[hello_hello]

Back in the 'olden days' when everything was still being broadcast in analogue and digital was in its infancy, Sony had some gear which supported 1125 lines. And Barco had some very good CRT monitors too.

The HP (Sony) Trinitron computer monitor I'm using at the moment, which is obviously progressive, goes all the way up to 2048x1536 (which would be a tad over 3k if CRTs had pixels). That appears to make it a QXGA (https://en.wikipedia.org/wiki/Graphics_display_resolution#QXGA_.282048.C3.971536.29) monitor. It seems that's the limit (https://en.wikipedia.org/wiki/VGA_connector#Cable_quality) for a VGA cable. How would the 2048x1536 limit for an analogue cable translate into required broadcast bandwidth? I've no idea.

Did CRT computer monitors ever get bigger than 22" inch, at least monitors capable of that sort of resolution? I'm not sure I've ever seen one in person if they did.

Anyway... the monitor has no problem displaying 2048x1536 at 85Hz, although I'm not sure when that much resolution on a 22" CRT display would be useful. Text becomes somewhat tiny. :)

[Katie Boundary]

Infinite minus one

Ah, you finally see things my way :)

You say nothing about pixel width nor framerate nor physical sizes... it all is inter dependent upon other parts of spec.

So in other words, you can make a CRT with whatever number of scanlines you want as long as you're willing to sacrifice other specifications? That sounds a lot like exactly what I've been saying this whole time.

So I would say that your question 1) amounts to "How long is a piece of string ?".

No, I'm asking for the maximum possible length of a piece of string, regardless of what it's made of or any other practical considerations, because you all claimed that such a limit existed, and now you're yammering on about how there's only a finite number of yaks in the world and you refuse to make string out of anything but yak fur even though I already told you I don't give a shit what the string is made of.

[StainlessS]

I've tried my best, it was lacking, I give up.

[hello_hello]

So in other words, you can make a CRT with whatever number of scanlines you want as long as you're willing to sacrifice other specifications? That sounds a lot like exactly what I've been saying this whole time.

Sounds more like a funny attempt at backpeddling to me. You said "nothing about CRT technology inherently prevented us from making a TV standard with 100,000,000 scanlines or any other number we wanted". Are you really trying to claim that wasn't based on the assumption the picture needs to be watchable?

No, I'm asking for the maximum possible length of a piece of string, regardless of what it's made of or any other practical considerations, because you all claimed that such a limit existed, and now you're yammering on about how there's only a finite number of yaks in the world and you refuse to make string out of anything but yak fur even though I already told you I don't give a shit what the string is made of.

As you've been shown, although you continue to ignore it, when the BBC began broadcasting, a little over 200 lines per 1/50th second was the limit of CRT technology, so that was the maximum length for a piece of string at the time (resulting in 405 line). Please explain how they could have implemented a 100,000,000 line system as you've claimed.

Here's some more information for you to ignore:
NTSC Lines_and_refresh_rate (https://en.wikipedia.org/wiki/NTSC#Lines_and_refresh_rate)
The actual figure of 525 lines was chosen as a consequence of the limitations of the vacuum-tube-based technologies of the day. In early TV systems, a master voltage-controlled oscillator was run at twice the horizontal line frequency, and this frequency was divided down by the number of lines used (in this case 525) to give the field frequency (60 Hz in this case). This frequency was then compared with the 60 Hz power-line frequency and any discrepancy corrected by adjusting the frequency of the master oscillator. For interlaced scanning, an odd number of lines per frame was required in order to make the vertical retrace distance identical for the odd and even fields, which meant the master oscillator frequency had to be divided down by an odd number. At the time, the only practical method of frequency division was the use of a chain of vacuum tube multivibrators, the overall division ratio being the mathematical product of the division ratios of the chain. Since all the factors of an odd number also have to be odd numbers, it follows that all the dividers in the chain also had to divide by odd numbers, and these had to be relatively small due to the problems of thermal drift with vacuum tube devices. The closest practical sequence to 500 that meets these criteria was 3×5×5×7=525. (For the same reason, 625-line PAL-B/G and SECAM uses 5×5×5×5, the old British 405-line system used 3×3×3×3×5, the French 819-line system used 3×3×7×13 etc.)

100,000,000 is an even number of scanlines, isn't it. :)

[hello_hello]

The "vertical retrace distance" in the info above had me a little perplexed in respect to the requirement of an odd number of lines for interlaced scanning. I think I understand it a little better now, and those half lines at the top and bottom of the picture.... the "vertical retrace distance" seems to be what they're about. Ahhhh.....

back to reading this and trying to get my brain to absorb it.
Interlaced Scanning (http://www.infocellar.com/television/scanning.htm)

[johnmeyer]

There are too many designs elements that interact to answer the questions. Perhaps another way to approach it, assuming we are talking about what can actually be achieved in this real world, and within the constraints of the laws of physics, is to look at what was actually achieved before the CRT gave way to LCDs and digital technology.

Runco (and Barco) were at the top of the high-end CRT manufacturers. In order to get the most out of an SD signal, they would first double or quadruple the number of lines using a Faroudja line quadrupler. This was then fed to a CRT that was capable of 2x the normal number of scan lines, and was also displaying at 60 frames per second, progressive (i.e., 60p). Here is the description of one such product:

Runco DTV-991 CRT Projector (http://www.avrev.com/home-theater-front-projectors/crt-projectors/runco-dtv-991-crt-projector.html)

The price of the line doubler and CRT projector together was $50,000 (1999 dollars).

This represented the most that any engineer could design and build. It was designed for a crowd that would pay anything to get better quality. If 2,000 lines or 4,000 lines could have been built, it would have, but this was pretty much as far as they could go with CRT technology.

So, rather than argue theoretical points, as an engineer I look to what was actually built and claim that, like the old Oklahoma song, it "was about as fer as they could go."

[Katie Boundary]

If 2,000 lines or 4,000 lines could have been built, it would have, but this was pretty much as far as they could go with CRT technology.

Errr, no, that was just the fanciest hardware that anyone wanted to build for the purpose of displaying standard-definition (480i) content. CRT computer monitors with resolutions of 2048x1536 used to be quite common, and a hell of a lot less expensive than $50k. The main reason why we never went higher was because, for resolutions that high to mean anything, the screens had to be quite big, and while a 4-foot-wide CRT might be suitable for a home theater (which would only be displaying 480i content anyway), it's definitely not something to put on your desk.

Sometimes, the real reason why things don't get built is because they're stupidly impractical, not impossible (https://www.youtube.com/watch?v=bvYUq6Ox0Hc).

[hello_hello]

Errr, no, that was just the fanciest hardware that anyone wanted to build for the purpose of displaying standard-definition (480i) content. CRT computer monitors with resolutions of 2048x1536 used to be quite common, and a hell of a lot less expensive than $50k. The main reason why we never went higher was because, for resolutions that high to mean anything, the screens had to be quite big, and while a 4-foot-wide CRT might be suitable for a home theater (which would only be displaying 480i content anyway), it's definitely not something to put on your desk.

It's no different to claiming there's nothing about aviation technology that inherently prevented the first flight by the Wright brothers from being in a supersonic jet aircraft. Well maybe that wouldn't be quite as silly as your 100,000,000 scan line claim, given we do have supersonic jet aircraft now.

You haven't tried to explain how it'd be possible, leading to the obvious conclusion you have no idea, and you're vainly trying to defend a claim you simply made up.

[johnmeyer]

This conversation is so pointless ...

[nussman]

We had an interessing conversation but then you all decided to argue with this Katie troll.

Imho for pal (ntsc as well) interlaced content via DVB is still very important.
We need 50 or 60 fields/frames per second for video content (quick sport etc.) and for original 24p/25p content a 50i/60i broadcast is lossless.
Using 50p for original 24/25p content doesnt make it "better". Its just need more satellite bandwith.

My question: Is switching between 25p and 50i/p covered by DVB broadcast standards (DVB-S2 etc.)?

[kolak]

Not sure, but BBC transmits movies as 25p and other programmes mostly as 50i, so this works.
50p may not be in DVB-S2 spec.
TV stations are also not so happy to invest money into bits which won't translate directly into bigger profits. People would not even notice that they watch 50p not 50i :) Stations are more interested in capping bandwidth, so they can start another channels which in 50% transmits adverts :)

[nussman]

Ah ok. That's cool. :)
25p/50p would be even better.
We get 720p50 here in germany, so its possible via DVB-S2 but I dont think 720p50 makes sense for the most content.

[wonkey_monkey]

Not sure, but BBC transmits movies as 25p and other programmes mostly as 50i

Not mostly - entirely.

Edit: sorry, I misread your post. What I meant to say is that, to the best of my recollection, all BBC HD output is only ever 1080i50, doing the same kind of "wrapping" as happens on what would otherwise be 1080p25 Blu-ray, for example.

That's broadcast output. iPlayer uses 720p25/50.

[nevcairiel]

50 fields are 50 fields, the only difference is from which point in time you take them. Both from the same time and its progressive. Technically they call this "progressive segmented frames" (PsF). Add some signaling to tell the receiver not to deinterlace, and you're done.

Or as an alternative, use 2:2 pull-down (ie. telecine), which is strictly speaking not the same thing as PsF, but thats probably just because different organizations standardized those.

[kolak]

Not mostly - entirely.

Edit: sorry, I misread your post. What I meant to say is that, to the best of my recollection, all BBC HD output is only ever 1080i50, doing the same kind of "wrapping" as happens on what would otherwise be 1080p25 Blu-ray, for example.

That's broadcast output. iPlayer uses 720p25/50.

Possibly, but my TV is showing me 1080p for movies and 1080i for most other things. There is something different in how they send movies which allows for TV to switch to 25p mode.

[kolak]

This is some hint:
https://ukfree.tv/article/1107051635/Freeview_HD_will_be_1080p25_and_1080i25_

And this even better:
http://www.bbc.co.uk/faqs/help-receiving/bbchd_channels_schedule

I'm using Freeview.

[kuchikirukia]

Does anyone even broadcast in 50/60p? Because anything under 50fps is garbage.

[manono]

Does anyone even broadcast in 50/60p?
There are US channels that broadcast 720p60. Earlier posters mentioned 720p50 in Europe.

Because anything under 50fps is garbage.
So, virtually every movie you've ever seen in a movie theater is 'garbage'?

[nevcairiel]

Some german stations broadcast in 720p50 instead of 1080i50 like many others.

[sneaker_ger]

Plus 1080p50 on German DVB-T2.

I believe 720p50 was kinda recommended by the European Broadcasting Union (EBU) so there ought to be other countries using it as well.

[Sharc]

I remember that 1080i vs 720p created a lot of emotions when HDTV broadcasting was introduced. Eventually we got both.

Just an example from the "pro 720p" campus:
http://www.bluesky-web.com/numbers-mean-little.htm