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jmac698,

The current test pattern was made available at the request of this forum's members. I added several elements to make it compatible with CBC's monitoring and alarm system. Your patterns would not have that material.

Secondly, I don't think it would be wise for me to start airing submissions from the general public. So thanks, but no thanks.
 

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jmac698 said:
To put this in plain english, did the upconversion box force a color conversion?
Are we talking about the 10 minutes of HD bars at the start of the programming day? Those are true HD bars, not an upconvert.
 

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measurements

The measurements I took were from a recording at 6/29, 2:15 EST, on CBC HD. They had SMPTE color bars with PLUGE, -I at 20IRE, and animated logo in the bottom right hand side, and were 4:3. I will definitely have to catch those HD bars.

My interest, which applies to very few people, is to automate the process of calibration on an HTPC. If the colorbars are off by +-2 it doesn't matter, as long as I know what they are, the program can do the calculation.

I have been able to calibrate an analog TV card to within +-1 of perfection, at worst.

The benefit of new colorbars to the general public are probably nil, as you can't adjust a TV by eye to that precision anyway. However, a test of color standard, or deinterlacing performance, and aspect ratio could be useful -- of course, that's up to you folks to debate :)

And Marc, thanks for the quick response, and I won't say anymore until I've done a thorough doublecheck of my testing methods. Anyhow, it's more for my curiosity of tracing the signal from source to home. And I didn't mean to imply that you had done anything wrong with the colorbars, it's fantastic that they are even there and I'm amazed everytime I see the communication you provide to the public.
 

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FYI, the files at www.w6rz.net are made in this way:
"The color bar patterns (and in fact, all the patterns on my website) are authored directly in 4:2:2 YCbCr. There's no conversion from RGB. I then use a DVS uncompressed file server connected to a hardware real-time HD MPEG-2 encoder over HD-SDI. It's a "bit perfect" environment.

I also spot check patterns with an in-house professional bitstream analyzer." - w6rz, the author.

I'm am working to have my test clips from CBC-HD, as received, analyzed in his "professional bitstream analyzer". I'm just curious if we receive bitperfect signals in our homes all the way from CBC.
 

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To be clear, the primary purpose of the upconverted signal is to keep our monitor alarms from triggering between sign off and sign on. It's not a serious calibration tool.

We have a number of probes across the country that trip an alarm in Toronto if certain signal parameters are not met for a period of time. That test loop has just enough audio, video and data to keep the alarms silent. If we didn't run this loop the alarm would sound causing a distraction for the operator who is monitoring programming in other time zones.

The real HD pattern airs just before sign on. Check my earlier post for the time and other details.
 

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rec.709

The signal I get here has a flag in it which specificly says to decode with rec.709 matrix. It's called a sequence_display_extension. If you make recordings with an HDTV card, you can check yourself, download Elecard Streameye, use it to open your file, click the headers tab, click sequence_display_extension, click colour_description.

Digital tv (and mpegs, divx,...) is stored as a brightness plus two axis of colors - imagine a color box rainbow, the color you want is at x,y... well this is called U,V. So Y, U, V is the color. A formula called a matrix converts this to the RGB your display uses. There are various matrixes, but two common types are called rec.601 or 170M, another is called rec.709. If you specify "green" with rec.601, but decode with rec.709, the green changes to an innacurate color (in this case, a brighter green).

All HDTV should use rec.709, but all sdtv should use rec.601, that's why Marc griped about "resolution independent production". Also, the SD colorbars had to have the video stream rewritten, so that it would come out right with rec.709. That means the numbers in the video had to go through a conversion matrix, which adds slight errors as these are integers. That's probably why I could measure +-2 differences.

The proper values for PLUGE are Y=7 (blacker than black), 16 (black), 25 (dark grey).

Why do all this conversion? YUV compresses better. However, you always lose a little accuracy as cameras work in RGB so at least two conversions occur (as integers) before you see the picture again :(
 

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jmac698 said:
The proper values for PLUGE are Y=7 (blacker than black), 16 (black), 25 (dark grey).
Forgive me if I'm wrong, but I think that you are mixing up the use of Y in this.

The numbers you are using to describe the black level should be RGB (or more correctly R'G'B', I always mix up the two) values.

As I understand my Poynton, the correct way to manage colour conversions is to always use RGB as the basis. In other words you should always author the source in the appropriate RGB space and then use the 601 or 709 matrix to generate the YCbCr values.

Similarly, if you are receiving YCbCr and you want to calibrate, you should use the appropriate transform to get back to RGB and use those values as your standard.
 

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PLUGE values

SMPTE 170M-1999 has all the info you need. White is defined as 100IRE and setup as 7.5IRE.
An improvement was made in SMPTE EG 1-1990 Color Bar Pattern which has the PLUGE and other bars.
The +-4 refers to IRE levels (an NTSC unit). IRE stands for Institute of Radio Engineers (now called IEEE). PLUGE stands for Picture line-up generator. 100 IRE is defined as white, and blanking (blacker than black) is 0IRE. There is 7.5IRE setup to reach black, so there is 92.5IRE from black to white. So 1 IRE=219/92.5=2.37 of Y units.

IRE Y R=G=B
-4 7 -11
0 16 0
4 25 11

It's somewhat arbitrary to use +-4 IRE though, and yes you need to now what RGB is produced by your device, because that is what will be displayed. I usually think in terms of Y because I get to look at the digital signal before it's converted which gives me slightly more information on the accuracy of the source. I like to isolate each conversion separately in each device, in fact with the color yellow I can tell if there was an 8bit matrix or a 10bit matrix.
 

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You should be careful about using IRE as a unit since it is a relative scale and is often confused.

As an example, what does 100IRE really mean on a digital interface? In the analog NTSC world it usually mean reference white = 0.7V. But in digital video reference white is R=G=B=235. Anything above that is the so called whiter than white or "peak white".

If you haven't already done so, I'd suggest taking a look at Poynton's website. There are a couple of really good papers there that cover this in detail.
 

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I agree about IRE; be careful when relating to physical values. I also agree to not believe everything you read on the internet (such as my statements). It took careful research to convince two open source programmers to agree on the correct colorbars, over a few weeks. As a philosophy, I hope to see ideas adopted solely on their merit, as I believe this is fair and unbiased.

This quickest evidence I can give you is this:
Rec. ITU-R BT.801-1, Annex 2, P13-15, http://www.itu.int/rec/R-REC-BT.801-1-199510-I/en
Code:
Rec. ITU-R BT.801-1
Description of encoded colour-bar signals according to the 4:2:2 level
of Recommendation ITU-R BT.601
100/0/75/0 colour bars
color		Y	Cb	Cr
white		235	128	128
yellow		162	 44	142
cyan		131	156	 44
green		112	 72	 58
magenta		 84	184	198
red		 65	100	212
blue		 35	212	114
black		 16	128	128
SMPTE 170M-1999, Page 7, http://www.smpte.org/smpte_store/sta...&CurrentPage=5
Code:
White Level.....100IRE
Black (Setup) Level... 7.5IRE
Derivation, 92.5IRE=[16,235]. You can do the calculations yourself. We must both agree, as long as we can agree that the two black and white points are the same ones. I support the current derivation by this measurement:

Source: Sony DVW-A500P (internal pattern-generator)
Digitized with: Avid Adrenaline Nitris (OMF 1:1)
(all values agree with the tables in the standard, and with my calculation)

Also, my measurements of CBC HD agree:
Code:
IRE area   Y code
black	16
+4	25
(the -4 IRE area reads 16, I don't receive blacker than black)

I have also collected a dozen colorbar pictures from the internet (including the greatdv site), and found that all of them are wrong. (colorbars of the web, http://forum.doom9.org/showthread.php?p=800670#post800670)

http://www.greatdv.com/video/smptebars3.htm which advertises NTSCBARS.BMP from Adobe has been proven wrong. We concluded by calculations that this was an analog capture. The picture is noisy and doesn't correlate in any linear way to either the tables in the standard or to calculations. Trust me it took a long time to prove it wrong, it had the effect of reputation, this made people biased to avoid giving the ideas merit. A good lesson in psychology.

Follow the long arguments here:
http://forum.doom9.org/showthread.php?t=108266
http://forum.doom9.org/showthread.php?t=107682&page=2

ps I have a copy of "An Introduction to Digital Video", Charles Poyton. Also, you can mathematically construct a matrix to convert rec.601 directly to rec.709 without any reference to RGB. If you use RGB, sometimes you can get negative numbers which can't be displayed, for example -4IRE is R=G=B=-11. -I and +Q also can't be displayed in RGB.
 

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Any ideas if the HD test pattern is still running or if it will again soon? I have recorded after the sign off time and befrore the start up but only appear to be getting the SD pattern. I have neen using channel 802.

Thanks
 

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The HD pattern should be on all CBC english stations, with a possible exception for CBOT-DT Ottawa. Channel 802 doesn't mean anything to me without your location and service provider. Including that data in your user profile is a good thing.
 

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Last call for the HD test pattern. CBC goes 24/7 on Monday.
 

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Last call for the HD test pattern. CBC goes 24/7 on Monday.

wow I can't believe I've just discover this thread... as I am a big calibration freak!

I've recorded a 1 minute clip of your HD colorbar test, and this is quite great, thanks!

but I will have love to be able to keep a saved clip of your complete set of 15 minutes test patern that you seem to have run in the past.. any chance your might run it one last time before the CBC HD goes 24/7 ?
 

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I think Lunnar is referring to the HD test pattern compilation tape I ran many months ago. Sorry, but that won't be airing any more.
 

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So is tonight (saturday October 7th) the last night that CBC will be running the HD test pattern on CBCHD?? I tried recording it last night with my PVR and when I watched it today it came out in the 4:3 (SD) format... I'm with Shaw Calgary, and was recording channel 309.
 

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If anyone in the Toronto and West areas are interested I have a Spyder2 Pro that I will rent out for a small fee. Just drop me a PM
 

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farfromover

If recorded the up-converted SD signal, you recorded at the wrong time. Did you record between 2:45 and 3:00 AM PDT or, I assume, 3:45 to 4:00 AM MDT?

From what Marc has said, I assume it should be on for the last time tonight at 2:45 AM PDT or 3:45 MDT on Sunday morning October 8 for 15 minutes.
 
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