The BBC's electronic TCF generator. Does anything like this exist outside of the BBC?

[TonyDuell]

One thing that worries me is that I would be very surprised if the Science Museum had made a backup of said EPROMs. Meaning they will be lost for ever when they develop bit-rot.

[inaxeon]

I have emailed them about it. If they ever respond I am going to tell them this. Surely they have people who know how to do stuff like that.

[PaulM]

Originally posted by inaxeon
Surely they have people who know how to do stuff like that.

Hmmm., seems highly unlikely in my experience with the Science Museum.

We use a hybrid chart constructed from a standard F card from 'Test Card Maker', but with a 'new' insert of the girl from a high-quality 35mm slide that can be found online. It's then converted to a BMP at which point text can be added using something like 'Paint'. Finally, it's uploaded to surplus Oxtel 'Miranda' image stores which output SD SDI. That can then be converted to RGB or PAL as required. Our 'Mirandas' have been modified for SS hard drives and they work really well. The files must be 'native' at 720x576. I know it's not EPROM, but it does the job in our OB trucks and workshops with several versions for the likes of 'IBA Southern' etc. We've also committed Test Card C and Marconi No. 1 to the 'Miranda' and they can be selected as required.

BTW, Test Card F is not solely copyright BBC. It was shared with the now defunct IBA and BREMA. Interesting thread here:
https://forums.digitalspy.com/discus...wns-testcard-f

Personally, that wretched clown doll always gave (gives) me the creeps - something out of a horror movie! Ughhhh!

Best regards,

Paul M

BECG www.becg.tv

[inaxeon]

Yes and there is a good point in all of this. I've had further discussion Richard Russell who is combative on this topic. He argues it doesn't matter about the TCF generator hardware because its output is arguable inferior to the original optical version. I guess if we mostly only care about the test card its self then that is true.

I personally wouldn't take that view. It is a real thing that people went to a lot of trouble to build, and it generated a version of TCF that millions saw on their TV screens. It would be a shame if it were lost because the necessary measures weren't taken to preserve it.

[PaulM]

We use our versions as a tool and as a reference image for visitors. For a quick line-up and check, it's pretty good, but it's a 'summary' chart - a jack of all trades. For measurements, it's no good - you need specific test charts and/or electronically generated waveforms. It has its uses, and the 'Miranda' is a good delivery tool of high quality.

The original analogue generated version would likely have been sourced from a flying spot scanner (FSS) using a 35 mm colour slide. They were far from perfect, although good. For geometry, they relied on the scanning CRT linearity and stability to be perfect and consistent which it could never be 100%. The colorimetry would have been good, but, again, far from perfect, albeit not quantised. The frequency response (both LF and HF) depended on many tweaks - again, something needing setting-up and maintenance. Smoothing of diagonal lines would be inherent to the analogue scanning. Gamma would be analogue electronic - again not perfect or fully stable. Always some noise with FSS, but given the correct exposure, quite acceptable.

The older monoscope cameras for test card generation could never be colour, so they were out of the question, although it may have been possible to use one with a colour insert from a FSS. They still had all the same CRT issues of geometry etc.

A mixed bag really, and it assumes that the FSS was kept operating to a very high standard. The digital version may be quantised and flawed in some areas, but at least it would have been consistent. It would also have been cheaper than a FSS - especially as they needed new tubes fairly regularly for top quality reproduction.

I still hate that clown!

Best regards,

Paul M
BECG www.becg.tv

[inaxeon]

Originally Posted by PaulM

A mixed bag really, and it assumes that the FSS was kept operating to a very high standard. The digital version may be quantised and flawed in some areas, but at least it would have been consistent. It would also have been cheaper than a FSS - especially as they needed new tubes fairly regularly for top quality reproduction.
BECG www.becg.tv

That is really interesting. I have to say this kind of information about flying spot scanners isn't something I've come across before. Pictures of them are also hard to find.

So in conclusion the optical TCF perhaps was higher fidelity, but the electronic was more consistent. I'm certainly not disappointed by that. Very interesting to me because I came into this with a focus on software generated complex test cards, and from the BBC's own materials it is indeed such a thing, and a very early example of one at that (except the central photo).

[inaxeon]

Originally Posted by inaxeon

He argues it doesn't matter about the TCF generator hardware because its output is arguable inferior to the original optical version.

Amendment to that statement, it actually said inferior to a digital image of the test card (due to digital->analogue conversion losses), not the optical test card.

[PaulM]

There was no digital in the early days, so no conversion at all. Analogue end-to end. Much depended on transmission losses through the whole analogue chain, the maintenance standards throughout that chain, and what was considered to be 'acceptable losses'.

The world changed as <<digital>> started to take root. The IBA's DICE was arguably the beginning of that new era. The BBC didn't like the 'upstart' making the pace, but DICE was a watershed, and for 1973, a truly remarkable piece of kit. An all-digital 525-625 standards converter? Now that was revolutionary and a digital test card F was nothing in comparison! Yes, we have a DICE - an incredible piece of kit which ushered in the digital era.

This is the production version:
http://marconiintelevision.pbworks.c...0Converter.pdf

Don't let me put you off your quest - it's useful - but so too would making our DICE work properly!

Best regards,

Paul M
BECG www.becg.tv

[Cathovisor]

Originally Posted by PaulM

The original analogue generated version would likely have been sourced from a flying spot scanner (FSS) using a 35 mm colour slide.

Cintel or BBC BA/10, I wonder?

[PaulM]

BA/10 is possible in the 70's, but I don't know how good/bad it was. Earlier BBC developed models would be a possibility, as would - as you suggest - Cintel. The latter had IP and patents on the technology of CRT based FSS, so I'm surprised that the BBC felt empowered to develop something like the BA/10 at the time. Cintel closely guarded their IP and that's probably why (so far as I know) nobody took up licensing the design. Perhaps it wasn't very good? Marconi was bitten over the technology and it probably scared folk off until patents expired. Another of the 'don't know' bits of TV history which needs research.

P.

[PaulM]

BA/10, good or bad(?) is here: http://www.bbceng.info/EDI%20Sheets/10097.pdf

P.

[inaxeon]

Wow. That is a monster. Full height rack! It has enough knobs and dials to keep even the keenest very busy and a socket outlet or three for the cleaners to plug their hoovers into!

[PaulM]

Nah, that's a baby. You should see our Cintel 'MkII' FSS telecine - now that's a big FSS machine - six 19" rack bay equivalent. It still has to go up to our museum from here, but haven't summoned up the energy or resources yet . . .

Best regards,

Paul M
BECG www.becg.tv

[Station X]

Thread restored to public view following editing.

Can we stay off the subject of Intellectual Property and Copyright as much as possible please. The discussion was starting to get confrontational.

[PaulM]

FSS is a very old TV technology dating back to the late 1920s using mechanical television techniques. Manfred von Ardenne is credited with its incarnation in CRT form. See: https://www.earlytelevision.org/ardenne_fss.html

CRT based FSS soon found its place in post war TV for telecine and slide scanning. It's full of problems but a basic scanner was always a favourite for Amateur TV using the ubiquitous 931A photomultiplier. I built my first one as a teenager with said 931A in a slide projector where the lamp should be, looking at a blank raster from a portable TV. With the right LAG (Long Afterglow Correction), the monochrome pictures from 35 mm slides were really very good. What I really needed was a short-persistence CRT and one was procured improving results greatly. Colour was much more tricky - short-persistence CRTs were usually blue/green with almost no red content. 'Coloured' pictures, yes, but 'good' colour, no. Eventually, at about 18, I acquired an EVR (Electronic Video Recording) machine which was a very clever 2 channel <<domestic>> FSS - monochrome with the colour encoded as 'stripes' on the B Channel. I found that there was some red content from the CRT and that using a dichroic and 3 photomultipliers, a colour picture could be produced from 35 mm slides. I wrecked that EVR in the process - I wish that I still had one - but it led me eventually to a work project for a 360 degree panning FFS for military imaging simulation. Worth the sacrifice, I guess! Would love to have one now . . .

What a shame the EVR wasn't made compatible with Super 8 film and 35 mm slides. Now that would have worked commercially rather than the quirky proprietary system which was a dead-end.

Unlike a 3 or 4 tube colour TV camera, the colour registration is perfect - it's the same raster addressing red, green and blue.

The bottom line here is that once the problems and limitations were understood, it wasn't that hard to produce quality pictures from an FSS. The BBC's BA10 is not something that I ever had any dealings with, but it wasn't that hard to make something that produced good still pictures. Hence the use of FSS for slide scanning using a short persistence CRT having enough red to deliver colour to an acceptable standard. The other problem was that photomultipliers had little red response, compounding the problem of poor reds, but with a bit of gain (and tolerating the noise), the red could be acceptable.

Better than a <<digital>> rendition? Yes, when all set up properly, but it would have been costly and not 100% perfect most of the time.

I believe that the colour bars at the top of the test card were electronically generated and keyed in, but I can't prove that. There were probably many iterations of the technology.

I still love FFS - it's clever and yet simple, at least in principle.

Best regards,

Paul M
BECG www.becg.tv

[inaxeon]

Originally Posted by PaulM

I believe that the colour bars at the top of the test card were electronically generated and keyed in, but I can't prove that.

In the BBC's own words:

"All of the geometric patterns were generated by computer techniques with reference to the original drawings. Edges were both horizontally and vertically anti-aliased to give the most accurate realisation of Test Card F. The central picture of the girl was copied from a side by means of a YUV 'picture grab', and the resulting data were inserted into the geometric pattern during the computer preparation process." (taken from this: http://www.bbceng.info/additions/201...%20(large).pdf)

Long story short. They re-did it almost from scratch thus it is a bona-fide, true electronic, software generated test card, probably the most perfect rendition of TCF ever. The process described is exactly how Philips designed test cards from 1989 onwards.

[Electronpusher0]

Originally Posted by inaxeon

I have emailed them about it. If they ever respond I am going to tell them this. Surely they have people who know how to do stuff like that.

When I e-mailed them about the 16mm projector I got a reply saying the query had been forwarded to Bradford, where the projector actually resided, I then heard nothing for a few weeks until they sent the scans so be patient, they are slow but helpful.

Peter

[PaulM]

Long story short. They re-did it almost from scratch thus it is a bona-fide, true electronic, software generated test card, probably the most perfect rendition of TCF ever. The process described is exactly how Philips designed test cards from 1989 onwards.

They did this with early 80s digital technology and it would be a standard analogue PAL coder anyway. By then it was possible to do even that digitally, but this looks like it had a normal coder. The devil is in the detail - for instance, how were the gratings rendered and other key features? They should have bandwidth limited rise/fall times with proper edges. You can do that in many ways, but with early 80s technology it wouldn't be simple. Was it mapped to sub-pixel rendition before entry to memory?

It would be interesting to see the output of the digital test card F and compare it against the original. Some aspects would undoubtedly be better - geometric accuracy and S/N ratio as two examples, but the subtlety of the transitions and the quality of the early 80s anti-aliasing would be debateable. 'Software' and 'digital' does not necessarily equate to 'best' or 'perfect'

Best regards,

Paul M
BECG www.becg.tv

[HurtyAC]

Hello all. What an interesting subject! I always wanted a testcard F generator when I worked in the service trade 1977-1980 but not possible until you had a VTR which I obtained in 1978. A Philips N1500 with a Test Card F off air recording, you can now use a DVD to produce a good result. For the three years I did television servicing there where two blemishes on the card, one on an upper right hand grey square and one on a lower left hand grey square. In 1980-1982 I worked for the BBC at Television Centre being posted to the Telecine Department which was on the 2nd and 3rd floor and we had some machines at Lime Grove where Nation Wide came from. When I had settled in I went to find the Test Card F slide generator which was kept in the Central Apparatus Room. It was a flying spot (CRT) slide scanner and I thought it was a Rank Cintel unit based on the Mk 2 Cintel Scanner but don't correct me on this as I only went to look at it mainly to see where and what it was? and guess what, there were the two blemishes that I had always seen so they where on the 35mm slide! Whilst I was there they always complained about the cost and time to maintain this slide scanner. In telecine itself we had 35mm Rank Cintel Mk1's, 16mm Rank Cintel Mk 2's an a 35mm and 16 mm Rank Cintel Mk 1 Polygon machines for variable speed film playback There where also some Rank Cintel Hopping Patch machines, that drove like a VTR, you could fast spool them. The new kid on the block were the Rank Cintel Mk 3 Digiscan machines. A digital YUV store bolted on their output, this enabling them to do both 525-30 and 625-25 video standards, the fancy stuff being done in the digital store. All the telecine machines gave out RGB and for use where fed to a PAL encoder.

Now onto testcard generators for us mere mortals. Dave Grant I think in collusion with Richard Russell came out with a Test Card C generator which I heard about but didn't expect it would be that good until I saw the unit at an amateur TV event, knocked my socks off! All the TTL logic circuitry had now been programmed into a MACH programable logic chip and the picture stored into two e-proms as before, it worked very well. Having got this I then wanted Test Card F so spoke to Dave with an idea I had which led me to Richard Russell to run the idea past him. He approved the idea and Dave produced the said Test Card F generator, it worked first class. I knew the copyright was not just the BBC's. I then wrote in turn to the ITC, BREMA and the BBC for use of the Test Card F image so it could be used by people with an interest in "405 Alive" and older TV restoration which was the only club/subscription open to people like us in restoring old television equipment. I was working closely with BREMA at the time on caption burn on the new Plasma TV's (1998) so knew them well. I wrote to all three and they all gave permission for us to use the Test Card F image on a non-profit or non-commercial basis but offer this to members on an "at cost" basis. This is how the Test Card F colour generator came about on Dave's TestCard "U" like site. I have the permission paperwork still from each party involved. The Test Card C and Test Card F images are stored as 8 bit samples which includes the sync pulses all clocked with a 12Mhz clock which is fine for a composite image maintaining subcarrier phase easily. Test Card C takes two e-proms and Test Card F takes 8 e-proms as it has to maintain an 8 field sequence including the bruch blanking so an 8 field image. On the Test Card C generator a 2 field image, again stored in two e-proms as you have to address one then the other to get the speed up. Don't forget in these earlier days memory and TTL logic speeds where rather low, as was e-prom addressing speed. Don't forget that composite saturation levels where only 75% on the UK analogue TV system which made the 8 bit sample levels work very well.
Hope this adds a bit more interest to this fascinating subject.

[inaxeon]

Originally Posted by HurtyAC

Now onto testcard generators for us mere mortals. Dave Grant I think in collusion with Richard Russell came out with a Test Card C generator which I heard about but didn't expect it would be that good until I saw the unit at an amateur TV event, knocked my socks off!

Ah yes Richard Russell, you may have seen earlier that I've already spoken to him about this. He dismissed my endeavour as being entirely pointless >:| (I suppose technically speaking everything we do here is pointless) but it is a bit disappointing considering that it turns out he was quite involved in all of this.

Thanks for the extra information, and I wonder if you had any idea who was originally involved with the digitisation of TCF? We know the outcome was probably pretty good, but who did it, and how? Back in those days the most high end computer (aside from mainframes) was an XT. This must have been quite difficult!