Friday, December 31, 2021

SDi physical layer measurement for 3G and 12G; a video presentation.

In the last couple of months I've had to do both training and fault-finding for SDi physical layer measurements. Below is a cut-down video of the half-day training; just so you can get feel for my training style.

I've also been working for a sports broadcaster tracing a problem they have with their incoming OB lines (all via a telco's private cloud J2K SDi route) - the problem was more fundamental than you'd think, but I got to the bottom of it.

I'm very pleased to have a Leader LV5490 with the physical layer measurement option; I can just rock-up at a clients and within minutes be able to give them proper eye measurements with jitter (both 10Hz wander and 10/100KHz-filtered readings). 

Thursday, December 30, 2021

ASUS ProArt PA32UCX monitor - LUTs etc.

My, my; it's been eighteen months since I paid any attention to this blog. Possibly the longest quiet period since I started writing it in 2003! Anyway - it's mostly down to work (I started Media Engineers at the start of 2020; a few weeks before the pandemic started).

Back in 2019 I was approached by ASUS to point a probe at their new PA32U (the first of their 32" monitors to carry the ProArt product name). It had a lot of issues and I wrote up my findings here. I also made a video showing my LightSpace profiling. 

In fairness ASUS issued a firmware update that took in my recommendations about DolbyVision and HLG. Also, in fairness they made their API available to the guys at LightIllusion which is just the thing - monitor manufacturers (almost) universally seem unable to make decent calibration software. 

SO, spin forward to the autumn on 2021 and an old pal sent me his new ProArt PA32UCX monitor and asked me to set it up for two SDR profiles and two HDR profiles;
  1. Rec.709 with a gamma of 2.2
  2. Rec.709 with a gamma of 2.4
  3. HLG - Rec.2020 colourspace with HLG 1.2
  4. DolbyVision - ST.2084 curve
At this point it's worth noting that I didn't have high hopes for the monitor for the following reasons;
  1. It's a single-layer IPS (LCD) display with an LED backlight,
  2. It's a FALD (so zone'd backlight) - like the Apple XDR it's an effort to make an LCD have a higher dynamic range. A typical 10-bit LCD panel (like an Eizo CG319X) can achieve about 1,000:1 but with a zone'd backlight that can be in excess of 1,000,000:1 but with the downside of halation around edges and transitions. Compared to dual IPS (think Eizo CG3146 or Sony HX-310) or OLED (typ. Sony X300) it's poor-man's HDR.
  3. They sell it on the strength of it having "quantum dots"(!) yet it can achieve about the same percentage of DCI-P3 colour space as a modern non-quantum LCD or OLED.  If QD actually exists then surely it should approach laser-projector like primary colours and so get close to Rec.2020 colour primaries? Non-intuitively you need monochromatic primaries to be able to get the largest colour-triangle and that's the promise of Quantum Dots - but since this panel does not have monochromatic primaries where are the quantum effects?!
So - my first thought was that rather than using the hunt & peck four-way controller I'd like to control the monitor from it's software. So, off to download ProArt Calibration 2.0 - first on my Windows 10 calibration laptop and then my other work laptop (15" MacBook Pro 2015 model) and finally my ancient workshop Windows 7 machine - none of them could communicate with the monitor.

I tried several different USB-C cables and eventually I had to resort to a powered hub to get Windows to recognise the device. However, at no point could I get the ASUS software to talk to the display (across three machines, three OSes). Thankfully ColourSpace was able to address the monitor and drive the internal patch generator (more about that later!) - but, first job was to use my CR250 (spectroradiometer) to make a matching profile for my K10A photometer. The reason for this is that the spectro is ultimately accurate but very slow and not good near black whereas the tri-stim K10A is great near black, fast (typ. sub 1 sec per read) but is bedeviled by Specral Power Distribution issues (the K10A is an RGB probe). BUT, with a profile made with the CR250 on the display concerned you can impose spectro accuracy on the photometer.
So, here's the matching profile - for my K10A on this PA32UCX

So, the next job is to profile the monitor so we can make the various calibration LUTs. For a 17-point 3D LUT you need to measure around 5,000 colours (17x17x17) and so even with the fast Klein probe you're looking at two hours. So - I set ColourSpace to drive the internal test signal generator on the monitor and went to make a coffee. When I looked in an hour later I realised something was very wrong; essentially the internal TSG does not seem to generate any blue?!

So, I had to break out my FSI BoxIO which I normally use for patch generation and start again. Two hours later I had a profile and could use ColourSpace to generate LUTs that corrected the monitor to the two rec.709 USER slots.  I saved out the various profiles as Builder Colour Space files (.bcs) and along with the LUTs I made you can grab there at

Now to the HDR settings and I discovered that you have to toggle the HDR-flag in the HDMI stream to get the monitor to switch into HDR mode which is plainly stupid for something that isn't a TV! No matter; break out the AJA Hi5-4K+ and use that to switch the monitor into both HDR modes.

Repeat the profile in ColourSpace and then generate the DolbyVision and HLG LUTs and use CS to upload them to the monitor. The results are not bad; here's a photo of the Eizo's luma scale in DolbyVision mode (so display-referred) and it shows around 650 Cd/m2 (not the >1,000 as their website suggests) once calibrated. In RAW/uncalibrated mode it can hit more than one thousand.

Last thoughts;

  1. If you put it into HDR mode, then switch the i/p to an SDR signal, disconnect/re-connect (which you have to do) it will then let you recall one of the SDR USER settings (so 1 for 2.4 gamma, 2 for 2.2 gamma) BUT it never takes the backlight back down to SDR levels - so you get rec709 with 500Cd/m2 white. You have to manually wind the "Brightness" figure back from 100 to 10
  2. "Brightness" is mislabelled - it should be "Backlight" or somesuch
  3. Brightness is actually called "Black Level"
  4. Their software proved useless - without ColourSpace I would have been left high and dry. 
  5. All this fiddling about took days (whilst I was doing other things) - I would not want to have been faced with this at a client's site. I won't be taking bookings to calibrate these monitors.
It's like a computer monitor they've hit hard with a hammer to kinda behave like a broadcast display but they haven't listened to everything the broadcast guy told them - I would not buy this monitor - for Rec.709 I'd use an Eizo CG-series and for HDR I'd use an LG or Panasonic OLED TV.

Wednesday, August 05, 2020

JVC DLA-Z1 4k projector; terrible calibration software!

I was recently asked to calibrate two JVC projectors for rec.709 and DCI-P3. These projectors have a modest amount of colour adjustment in their remote interface, but none of the factory presets are particularly accurate. For calibration JVC have their own software which is terrible! Why people don't integrate with LightSpace (particularly since Steve and his team are very keen to help manufacturers) I'll never know.
Anyway, before detailing two days of frustration in a couple of grading rooms it's worth reminding ourselves about the difference between Spectroradiometers (AKA "spectro) and Colourimeters (AKA "tri-stim probes")
  • Spectroradiometers measure wide band light energy - everything from 380nm (or lower) - very deep blue through to 740 (or higher) - very deep red. They are slow to make a reading (many seconds) and do not cope well with low light levels. 
  • Colourimeters measure just three wavelengths (just like your eyes) - which we'll typically refer to as Red, Green and Blue (but really are X, Y, Z colour matching functions) and so are vulnerable to metameristic failure (a mismatch between the primary colours generated by the display device and the filters used in the colourimeter) BUT they are fast (my Klein K10A can make a read in less than a second) and they are accurate all the way down to near-black.
So, best practise is to use your spectro to make measurements of primary colours (and peak white to be sure) and use that to calibrate the tri-stim. After that you have the speed and black performance you need with the accuracy of the spectro imposed. I tend to do this every time I encounter a new display even though the K10A comes with a lot of factory profiles and the trick the Klein uses is that their filters are very close to average human vision and so any metameristic mismatch between the probe and the display is close to perception which is all important.

Now, onto the JVC software, the first thing they neglect to tell you is to not run the network setting in DHCP mode if you want to do calibration; the projector tries to renew the DHCP lease every hour and so it's likely you'll loose connection and have to restart the process...

Next you have only two choices of low-end probe - the "DTP special" - the Spyder, and the only slightly better Xrite i1Pro2 spectro (I happen to have one of those) but bear in mind all the things we said about spectro earlier.
The Xrite needs to calibrate itself to it's supplied white reference tile every time you use it BUT the JVC software has not implemented that functionality - so, you have to load up some other software (I use Sony's monitor colour balance software), but LightSpace, ColourSpace or several others would do - connect to the probe, trigger a calibration and then disconnect.

Now you have to position the probe to collect enough light to make measurements - most projector calibrating gets done from the operator's position and probes like the K10A have aiming lights to show you where they are pointing at the screen. BUT, after two days of experimentation I found I had to have to i1Pro2 as close to the screen as possible whilst avoiding it's own shadow. It's marginally improved by offsetting it horizontally (so the long edge of the probe is parallel to the screen) as the shadow is not as significant;

These projectors have a setting for the LD power - you can drive the lasers at three different power levels. At the highest the image is too bright for grading work; around 120Cd/m2 at peak white which would be fine for a 31" grading monitor, but not a projector. At the mid-LD setting you around 60Cd/m2 at peak white which although still bright is OK. Again, what the documentation doesn't tell you is that it take around half an hour for the power to ramp up or down between LD levels. 

Finally, there is one other setting that can really kill you ability to get decent reads with the Xrite i1Pro2 probe and that's limited/full-range video on the input settings - yes! They have sited the internal patch generator before the video range decoder! So, with all this in mind if you don't;
  1. Have the probe as close to the screen as possible,
  2. Have the projector in High LD power mode for at least half an hour,
  3. Have the video input set for full-range video,
Then you will not be able to read a decent way up the 2.4 gamma curve for rec.709 (and the red channel is particularly affected). Have a look at the light levels as they are read;

This results in some terrible response in the resulting profile with the red channel in a terrible state, incorrect low end response and clipping close to black. 

However, if you get those three things right (above) then you get decent reads close to black and a proper response for the range;

How much easier this would have all been if you could use a tri-stim probe like the Klein but by limiting the software to using a Spectro you are bedevilled by low-light issues. Having to do your calibration at High LD and then switch the projector back to mid-LD when your done is silly. 
I suppose the reason it's like this is that these projectors are aimed at high-end domestic/board-room/lecture-theatre applications and not film & TV. The fact the software defaults all SDR gammas to 2.2 seems to indicate this and not having LightSpace support (when LightIllusion have offered to do all the API donkey-work) is unforgivable in the professional display device.

Sunday, May 10, 2020

Kickstarter projects; three out of four ain't bad...

Along with KickStarter there are numerous crowd-funding sites and I've ploughed a bit of money into several. As well as electronics projects I have funded a few artists to record albums and have been very pleased. 
Here are four projects I backed, three of which came out really well and one which kinda got half-way there. The thing you have to remember is that backing things on KickStarter is not like buying something - you have to fully accept that some project just won't deliver.

  • PockEthernet is a tester for ethernet and IP networks. Serious network people use a Fluke DTX-1800 (I used to have access to one) - it's now discontinued, but like the replacement DSX-series all TDRs (Time Domain Reflectometers) are expensive (a few thousand pounds) but if you want to certify an install it is expected. At the other end of the spectrum you have the £50 DC testers that just make sure there is continuity on each of the eight legs and really just allow you to have some certainty in termination polarity etc. The PockEthernet is a half-way house with some TDR capability (not sure home accurate is it) but nice record keeping. Above a little DC-tester (like a ModTap or others) it can do some IP testing; POE, DHCP, VLAN tags etc. and so for me is ideal. 

You interact with it using a BlueTooth-attached app running on 'phone or tablet computer

The measurement reports can be over many circuits (so testing a whole patch-panel at once is do'able) and you can email/save as PDF from the app.

You can even brand the reports with your logo

  • BeeLine bike navigator - I often see folks with their smart 'phone in a waterproof wallet as a bike GPS. That's great, but when I'm cycling somewhere I'm not entirely familiar with I often like to find my way but certain in the knowledge that as I get closer I can make better navigation decisions. The BeeLine is a bluetooth attached smart compass that tells you what direction to go and how far your destination is. I've been using mine for maybe eighteen months and it works really well. It is stable and accurate with good battery life.

wiggly route; it was a Sunday afternoon!

  • Pebble Smart Watch - Although the Apple Watch is undoubtedly a miracle to technology I never felt it was for me; the biggest problem is the battery life; two days at best. It also seems to need a lot of curation. Friends who use them are constantly attending to them and I only really wanted a second screen for my 'phone with good notifications, health tracking and control of media players. The Pebble does just those things really well and nothing else. The battery on mine (Pebble Time Steel variant) lasts for more than a week and when they went bust at the end of 2016 I bought a second one just in case. They charge in about an hour.

The lockdown has been great for sleep but very bad for exercise...

I always return to the same watch-face "Graphite Too" as it has everything I use and is clear.

Thankfully after Pebble went bust and got bought by FitBit a group call Rebble acquired all the source-code etc and have been supporting the watches with new firmware and online services since.
  • Oscilloscope Watch - I know what you're thinking; what a daft idea! I've written a lot about this one in the past because I did get a very janky alpha-version (3D printed case, very early build of the software etc). Still, five years on and the project is still live on Kickstarter and so we live in hope!

Thursday, March 12, 2020

Modifying Blackmagic 6G routers for quiet(er) operation!

You can't deny the value in BMD SmartVideo Hubs - they are a fraction of the price of traditional broadcast video matrices. They have appalling return-loss on the BNC inputs and their control system is very simple (although in lots of cases that's a benefit). The temptation is to stick them in desks in edit, grading and audio suites, but they are noisy! The reasons are;

  1. Cheap, low air volume fans
  2. Tiny holes in the chassis through which to try and pull enough air
  3. No control of the fans even though the ones they supply have a tach output

'scope is showing the tach o/p of one of the fans, yes, I was routing video!

Even though the cheap/noisy fans BMD fit have a tach output it clearly isn't read by the hardware as the fans run at full tilt from power-on. This one had been on and routing video for a couple of hours (with the lid on) and it's like sitting next to a vacuum cleaner.
So, quick look at RS and filtering by size, volts and then listing by highest air volume & lowest noise I got these Papst fans - they also have a tach output (I had no plan to use that) and more importantly are induction-start motors (so they will run on much lower voltages; I had a feeling I could simply control them with a potentiometer with a similar impedance to the coils).

getting them ready to fit in the same JST 1.5mm pitch headers as the stock fans, 10K pots

fitted to replace the stock fans - I had to ream-out the screw holes in the fans for the screws to fit, double-sided tape for the pots.

The other issue is the tiny holes they have in those cases for airflow. With a bit of extruded aluminium and grill material you can get a good look.

Make sure you don't put another piece of equipment directly above it!

So, proof of the pudding and all that; I ran the stock unit for a couple of hours, pulled the lid off and took a photo with my thermal camera and then did exactly the same after the modifications. The results speak for themselves; the client has these in their audio suite and game me four more to modify.

before & after - running cooler and maybe 20dBs quieter

As an aside I found driving these fans at a constant 8v produced the best results.

Friday, November 29, 2019

Rigol Ultrascope software and Windows

Ever since abandoning the faithful Tektronix 2245 oscilloscope I've been a fan of Rigol digital 'scopes; compact and a load of functionality for modest money (FFT and 1Gig samples/sec in my little DS1052E).
Rigol have been less than stellar in keeping the Windows software current and so here are some cobbled-together instruction (from amongst others - but his website is often down?).

  1. Download Ultrascope for your particular series (so DS1000E in my case)
  2. Download the Windows driver (had to find this on the Way Back Machine!), Extract these two files, then go find the device in the Device Manager. Update the driver and point it to the directory where you extract the driver files.
  3. Next, download the NI-VISA Run-Time Engine (v5.0.3 as of this writing). Beware, this file weighs in at 71 MB. Install the VISA runtime with the default options (you could probably get away with just installing the USB portion, but I didn’t try it).
  4. When the NI-VISA installer finally finishes, you might be prompted to reboot. I skipped this step :-). Run the Ultrascope software, and click on Tools –> Connect to Oscilloscope. I was prompted with a list of devices, with none of it making much sense, except the first option “USB0…”

Sunday, October 06, 2019

Experiments with white light (it's complicated!)

I've often run a day's training course for broadcast engineers who want to get up to speed with calibrating monitors and projectors; typically to rec.709 but increasingly to P3 as HDR and 4K/UHD are becoming a thing.  One of the principles I've always struggled to get over is Metamerism; that inability to see/measure colours correctly if your measurement device (camera, eye) is tristimulus and your source of illumination does not have a daylight-like spectrum (so LED lights, typically).

A few month's ago I got one of Chris Wesley's excellent home-brew spectroradiometer kits; from now on referred to as the ghetto-spectro.  Read Chris's excellent documentation about how you can make really quite accurate spectrum measurements with modest parts so long as you can accurately calibrate the thing - and this is where the spectrum of Mercury comes in useful. Mercury has two peaks in the visible spectrum at 546nm and 436nm and you can guarantee that a compact fluorescent bulb will have a decent amount of mercy in it.

the ghetto-spectro pointed at the mercury containing CFL bulb on my workshop bench

the measured output showing the various peaks of different elements

the image from the diffraction grating in the iPhos

So, watch Chris's video which tells you how to calibrate to the two Hg-peaks, and pay special attention between 540 and 550nm as Terbium lurks very closely to the 546nm peak (green) of Mercury.
Terbium is at 543nm, very close to Mercury at 546nm

OK, now I have a calibrated spectro I can turn my attention to experiments with white light and perception. I build a box with two isolated sections, painted inside with a very reflective white primer paint. In the left-hand cavity is one of those RGB-mixer bulbs based on LED technology (and controllable from an app; very 2019!) and in the right-hand section is a broad-spectrum white light. 

Thus equipped I can now mix the RGB values in the left-hand side to produce a white light that matches the right-hand side from my perception. As you can see; the camera in my iPhone does not agree! BUT, I promise you, to my eyes the two white are a really good match. I have spent may years "racking" studio cameras (matching their colourimetry for live TV shows so that the lighting director doesn't shout at you!) and eye-matching displays (typically a good domestic TV to a grade-1 broadcast monitor) - I have a better eye for colour than most.

So, at this point I should show the spectro output for the two light sources;

the right-hand broadband white light; reasonably continuous spectrum

the RGB-mixer bulb; three clear peaks

So; I took photos using three different cameras; an iPhone 8 using the native Apple photo app, a low-end Android tablet using the Google photo app and a 2015-vintage Fuji Finepix 5600 bridge camera. All three rendered the RGB-white differently (remember , that to my eyes it's the same white as the broadband white bulb) and they also minimized the differences in the colours of the juggling thuds I used as colour references in the two box sections.

From the iPhone 8

from the Android tablet

from the Fuji Finepix

Finally I should make a note of how my perception of the colours varied;

I need to think about this a bit more to relate the spectra of the two bulbs to the likely sensitivities of the cameras; but, it does show that observer metameristic failure is a things!