[cjgpers]

Good to see the blacker-than-black dot now clearly visible when I pushed the brightness up too high. Now, all we need is a decent 1440 resolution test on the testcard.

[Andy Quested]

Best way to record the test card. Check the off air time add 60 mins and record for 15 mins. So if we finish at 00:30, record 01:30 - 01:45. The test card is about 65 minutes into the promo loop. There will be another test signal (AV sync) as soon as we are happy with the signal. This will be about 50 mins after the test card but I will confirm that as soon as I am sure,

Andy

[Clive T]

Apologies (especially to Andy Quested) if I've got completely the wrong end of the stick on this one - this is my first post - but...

The colorimetry on the colour bars section of the new HD test card seems to be wrong. When I converted to RGB using BT709 colorimetry on PC I expected either red/green/blue peak level on bars to be about 235 (8-bit words) with black level at 16 or at levels 255 and 0 if re-scaled for PC use. Neither was true. The values I got on my capture system were very similar to those that I got from captured images that other users have posted. I've also checked on latest 'sub black' version today.

To keep the PC and RGB conversion out of the loop, I've kept things in the video domain. My test setup is: Pace DS810XE receiver feeding Focus Enhancements MCSDI-1 interface (in both HDMI and Y,PB,PR formats) then HDSDI feed to Blackmagic capture card or to Tektronix WFM5000 waveform monitor.

I assume that the colour bars are 100.0.100.0 (i.e. 100% bars - fully saturated at full amplitude). Looking at the test card signal, the luminance steps etc look OK for the monochrome areas of the picture except that peak white level (level 235 or 700mV) is set as the peak of the 'superwhite' dot instead of the normal white level. For 100% colour bars, I would have roughly expected to get the following voltage levels on the video signal (assuming BT709 spec):
White Bar: Y=700mV, PB=0mV, PR=0mV
Yellow Bar: Y=649mV, PB=-350mV, PR=32mV
Cyan Bar: Y=551mV, PB=80mV, PR=-350mV
Green Bar: Y=501mV, PB=-270mV, PR=-318mV
Magenta Bar: Y=199mV, PB=270mV, PR=318mV
Red Bar: Y=149mV, PB=-80mV, PR=350mV
Blue Bar: Y=51mV, PB=350mV, PR=-32mV
Black Bar: Y=0mV, PB=0mV, PR=0mV

What I measured on the Tek WFM5000 was approximately:
White Bar: Y=690mV, PB=0mV, PR=0mV
Yellow Bar: Y=590mV, PB=-245mV, PR=30mV
Cyan Bar: Y=490mV, PB=50mV, PR=-245mV
Green Bar: Y=440mV, PB=-200mV, PR=-245mV
Magenta Bar: Y=200mV, PB=230mV, PR=280mV
Red Bar: Y=150mV, PB=-70mV, PR=290mV
Blue Bar: Y=50mV, PB=290mV, PR=-20mV
Black Bar: Y=0mV, PB=0mV, PR=0mV

It a bit more obvious on the photos I've got! Essentially the luminance values seem to be incorrect on all coloured bars except blue, red and magenta. The PB and PR signals only reach peaks of +290mV and -245mV so are too low and assymetric. Obviously none of the vectors were in their boxes on the vectorscope display. Nor did the figures seem to match up with other theoretical colour bar saturations (eg 95% - 100.0.100.25 or 75% - 100.0.75.0).

Anybody got any bright ideas or am I completely on the wrong track?

Very good to see the test card back, especially in HD, and, yes, I did get the 'Test Card F' answer right on 'Have I Got News for You' last week!

[Andy Quested]

Well Mr Clive T I really do congratulate you on your knowledge and am envious of your home set-up (really) but you have just demonstrated why we cannot let out the true test card. You are correct the pk white level is the super white spot. This will make the pk levels slightly incorrect across the test but it is for domestiv display line-up only Also the colour bars are not 100% or EBU level. I did say in a previous post the pk white was not correct and therefore the grey scale would be slightly off. If you have a professional display to line up I really must point you to commercial suppliers.

Andy

[Clive T]

Thanks Andy for your most helpful reply. In fact you gave the answer I was rather hoping for... I was expecting the slight change in luminance level due to the peak white level but I hadn't heard any comments on the colour bar parts of the test card. I have to admit that colorimetry is not my strongest subject (I always to defer to anything written by Charles Poynton on that topic...) so I thought I was mis-understanding the BT709 colorimetry in some way - or, of course, that the colour bars weren't what I thought they were.
Thanks again and congratulations on arranging for the test card to be broadcast in HD.

Clive T.

[delphiplasma]

Hmmmm...I assume that the test card can only be used for the basic set-up such as geometry and black level settings?

I was hoping to try and check the calibration of my display with my colorimeter, however, I would have to calculate the readings manually, as I have a Plasma screen which I calibrate using 10% windows. Never mind, at least the geometry and black level adjust was of good use. Better than nothing.

Just got me wondering whether that SMPTE colour bar display I found is correct? I've already had my colorimeter on it and after a bit of calculation managed to get quite good results. The results also showed that I had the saturation level set a little too low.

Thanks for the information.

[Andy Quested]

There is another reason for not putting out the full test card - we have the rather embarrassing proof it does burn in after only a few minutes! The card is still good for many things though and now you have the figures kindly supplied by CliveT, with a bit of spread sheet work you can calculate the offsets to apply to you colorimeter.

Another update on the AV sync signal - we got to the bottom of the coder flashing on the AV sync test signal this afternoon and the modified version will be added to the master tapes on Monday or Tuesday - hope ot have it on air Wednesday night or Thursday. (sorry it takes so long but we need to check each step to make sure a AV sync test is actually sync!)

[delphiplasma]

Forgot about that, you're quite right with the burn in issue. I suppose that's why 90secs was chosen?

I'll work with Clive's findings.

Out of interest, if you were going to recommend a domestic flat screen display, which would enable the viewer the best image from the HD production, what would you recommend? Make and model.

I've always been under the impression that plasma is a cut above LCD when it comes to image quality. However, I see the BBC R&D have worked closely with Vutrix to produce LCD monitors. Chromaticity is suppose to be spot on and have adjustable gamma (Not sure whether they would meet the 2.35 EBU recommended level?) However, there are still issues with black level and poor screen backlighting uniformity over the entire screen and the fact you move off the centre axis the image quality degrades considerably.

Be interested to see if you have a recommendation for both LCD and Plasma.

Thanks

[Andy Quested]

In my blog i will be recommending the test card is only on for a maximum of 2 minutes for screen under 3 months old, and no more than 5 minutes for older screens. As for screens, I think this is a personal choice now - just like buying speakers. When I was looking around for an HD TV my first criteria was stunning HD but after I had a short list the one I bought did the best SD, after all even I watch quite a bit on SD channels. Re our work on HD displays, these are for the broadcast market not domestic, so unless you fancy paying about £500 per inch I'm not sure these are ready for the high street!!

[delphiplasma]

And another question..!(Sorry, seems that I've churned out question after question in such a short space)

Is it true that OFCOM (Or some kind of ‘OF…?) have allocated 4 HD channels on ‘Freeview’?

I hear that those 4 channels will use the BBC ‘DIRAC’ compression technology, to provide BBCHD, ITVHD, CH4HD and CH5HD. Would this form of compression mean a slightly degraded picture quality compared to Freesat?

If this does happen, what would the main HD platform be? Satellite or Terrestrial?

[Clive T]

Don't forget that HD on Freeview may mean 1280x720 pixels (progressive) not 1920x1080 (interlaced at present) as on Freesat. I guess move to 1080p on Freesat is awaiting 3Gbit/s production hardware and is a few years away. No doubt others will be more 'in the know' about what current thoughts are on both issues.

Clive T.

[Geordie_Cy]

Originally Posted by cjgpers

So, let me get this clear. With the new version of the BBC HD Test Card, I should be able to see all 4 white/black dots on my TV - the white, white-than-white, black, and blacker-than-black.

No, the brightness should be adjusted until one of the black dots just disappears, then contrast adjusted until one of the white dots disappears.

[Geordie_Cy]

Originally Posted by cjgpers

So, let me get this clear. With the new version of the BBC HD Test Card, I should be able to see all 4 white/black dots on my TV - the white, white-than-white, black, and blacker-than-black.

No, the brightness should be adjusted until one of the black dots just disappears, then contrast adjusted until one of the white dots disappears.

[2Bdecided]

Originally Posted by Geordie_Cy

No, the brightness should be adjusted until one of the black dots just disappears, then contrast adjusted until one of the white dots disappears.

If I understand correctly, then given the "adjustment" Andy has made to prevent this broadcast testcard being accurate, making one of the white dots disappear will actually cause your TV to clip below peak white in a valid and legal video signal.

In other words, if either white dot disappears, your TV is too bright (actually too much contrast).

Cheers,
David.

[Andy Quested]

new blog up now BUT the sub black spot is being chopped somewhere between Red Bee and Siemens! We are going to chase after end of programmes tomorrow morning.

The Blog explains (I hope) how to do it with pictures but for brightness
1. Turn up the brightness until you can see 2 spots in the black patch on the grey scale
2. Turn down the brightness until the right hand black spot (sub black) disappears BUT you can still see the left hand spot (2% above black)

However if they don't get it sorted tonight I will have to re-do the blog. You can do it without the sub black spot

1. Turn the brightness up until you clearly see the lighter spot
2. Turn the brightness down until it disappears
3. Turn the brightness up on number at a time until you can just see the spot against the black block on the grey scale

Contrast is a matter of choice - the broadcast test card has been modified (see the blog) so you should see two white spots at the top of the grey scale but some displays cannot handle that level of detail at peak white so as long as you can see the left spot AND you are happy with the "look" of the picture it's fine

Andy

[Andy Quested]

Black spot back! And the test signals are all going out as expected.

Andy

[delphiplasma]

Andy,

Regarding adjusting the vertical/horizontal scan size, when I adjust the test card so that the tips of the arrows are just touching the edge of the screen, the circle doesn't seem to be truly round, I have to provide a little more vertical underscan to get a perfect circle.

Would this be something to do with the fact my display has a native resolution of 864 lines?

I never had problems when I use to adjust 4:3 displays using the 4:3 test card, using the same arrow method above?

Thanks

[Dave-H]

Originally Posted by delphiplasma

Andy,

Regarding adjusting the vertical/horizontal scan size, when I adjust the test card so that the tips of the arrows are just touching the edge of the screen, the circle doesn't seem to be truly round, I have to provide a little more vertical underscan to get a perfect circle.

Would this be something to do with the fact my display has a native resolution of 864 lines?

I never had problems when I use to adjust 4:3 displays using the 4:3 test card, using the same arrow method above?

Thanks

Some LCD screens, especially the smaller sizes, are actually 16:10 panels, not 16:9.
To get the correct shape on 16:9 transmissions, you will either have to have some black lines at the top and bottom, or lose a bit at the sides.
Losing the side castellations at the left and right of the card will probably be pretty much it.

[guitardave]

I've calibrated my tv using the blu-ray of HDBasics, so the only adjustment I need to make for my tv viewing is whether to have my Sky+HD box contrast setting set to low, medium or high. Medium looks just fine to me.

I recommend HDBasics to anyone wanting a good calibration of their tv.



Dave

[dwhite]

Originally Posted by guitardave

I've calibrated my tv using the blu-ray of HDBasics, so the only adjustment I need to make for my tv viewing is whether to have my Sky+HD box contrast setting set to low, medium or high. Medium looks just fine to me.

I recommend HDBasics to anyone wanting a good calibration of their tv.



Dave

What you actually have done is calibrated your bluray player for your TV. It doesn't necessarily mean you can use those settings as calibrated for all inputs, as each source can have its own display characteristics. Although they are likely to be close and better than out of the box settings. Thats why the testcard is useful being broadcast on BBC HD, it allows you to now calibrate SkyHD or FreesatHD for your tv.

[delphiplasma]

Thanks, Dave-H

The screen is a 32inch Plasma 16:9.

So not that?

I can only assume there must be something a miss in my set-up if everyone else is getting a perfect circle with zero overscan.

Not to worry.

Thanks

[guitardave]

Just checked Anytime this morning, to be greeted with the "HD Christmas Test Card"! Fun!



Dave

[Orbitalzone]

Originally Posted by guitardave

Just checked Anytime this morning, to be greeted with the "HD Christmas Test Card"! Fun!

Dave

Wow what a poor test card that is!

It doesn't appear to be aligned correctly the lip sync test isn't a very scientific calibration either (plus is seems to vary) and then the card seems to go to SD mode at the very end.

And yes, my TV looks perfectly aligned using the BBC test card.

Still, it's marginally better than no test card I guess

[chris2k2]

Originally Posted by Orbitalzone

Wow what a poor test card that is!

It doesn't appear to be aligned correctly the lip sync test isn't a very scientific calibration either (plus is seems to vary) and then the card seems to go to SD mode at the very end.

And yes, my TV looks perfectly aligned using the BBC test card.

Still, it's marginally better than no test card I guess

Well I'm glad that with the santa card my new tv all looks good.

[chenks]

does anyone know where to get the UK/europe version of the DVE HDBasics ?
had a look on ebay and could only find RegionA US versions.

i would be playing the bluray on a UK PS3