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!

Monday, September 23, 2019

What I saw at IBC2019

Eizo CG3145 “mk.2?” – Revision of the current model “Prominence” monitor - see my post from last year.

It’s exactly the same dual Panasonic IPS (LCD) display module and modulated LED backlight as the current version (and indeed the Sony X310 replacement for the X300) with the following upgrades;
  1. Quad 3G and single-link 12G inputs for current gen 4K/UHD/HDR standards. If you need to go to 18G standards (so 4K, 12 bit, RGB and 60P) it still supports HDMI 2.0 and DP. Once nicety is that it has SDi out and can convert signal standard as an active loop-through (but not converting colour space, sampling structure etc – obviously),
  2. Internal probe; a higher quality photometer than the 319X but I’ll have to test it against a “proper” probe before we make comment; they assured me ColourNavigator’s “sensor correlation” function would work as other CG-series displays. See my video.
  3. Three user-defined cages and BITC as per Sony’s 4k monitors – this has been mentioned by several facilities as reasons why they won’t leave Sony – aside from the BITC feature having been broken in the Sony displays since v.2 firmware I don’t believe grading room displays need either of these, but it’s good to have an answer (I’d say exactly the same as point 1. Above)
  4. Much nicer control via a big knob on the front.
  5. Price – will be the same as the current CG3145
  6. Availability – they reckon there will be pre-production demo examples in January and supply at start Q2.
They made some point about having improved the FPGA code in the panel for better sharpness – sounded like marketing waffle; and in truth savvy customers don’t want a monitor “sharpening up” their pictures; pixel-to-pixel is what’s needed; brutal honesty rather than the picture processing you get on a domestic TV.

Emerald KVM system from Black Box; it comes in three product skews;
  • The basic – tops out at 2 x single-link displays (1920x1200) 
  • The “professional” – same performance but has tighter integration with their manager
  • The 4K – supports a single 4096-pixel wide display.
Points to consider;
  1. Price – the basic and professional are very akin to Amulet pricing (bear in mind Amulet Tera2 products do 4 x single link or 2 x 4K displays) – so typically £1,000 per end-point (sender and receiver); Amulet external T2 would be £1,400 (sender) + £700 (receiver). The 4K product which is what now competes with DX-H4T/DZ4 from Amulet is around twice the price (about £3,900 for sender/receiver pair). Add onto this the cost of a broker (their own 1u Linux box) AND they heavily push you to Black Box managed switches (essential if you’re using all the broker features),
  2. Encryption – AES256 with key-exchange is the clear via the broker’s database; we couldn’t sell this to anyone who is looking at a TPN audit,
  3. Bandwidth – max’es out a gigabit Ethernet (in fact you need the second NIC if you want to use two screens); remember, Amulet plays nicely with internet-type bandwidths
  4. Switch requirements – As mentioned, BlackBox manages switches preferred, but whatever you use jumbo frames and IGMP-snooping is required. Amulet plays nicely with all layer-2 ethernet switches.
  • Broker is better to use than Tera connection manager
  • ZC supports both PCoIP and RDP (their protocol is Windows RDP!)
  • As you’d expect from a modern KVM it is reasonably transparent, but full-screen HD video playback was (I thought) worse than Amulet (and remember Amulet tops out at 200Mbit/sec rather than the 2 x GigE that the Emerald needs)
So in fairness I don’t think there is any scenario (other than owning existing plant) where we could sell it as a better option than Amulet (or a Teradici option).

Streambox’s DolbyVision remote workflow

StreamBox have implemented eCMU functionality in their Chroma range which means they can take the DolbyVision metadata across the IP-SDi feed and decode the rec.709 fold-down data at the far end and display dual-6G outputs on and HDR monitor and a rec.709 display (typ. a decent TV). The powerful thing is that by having the Dolby tone-mapping algorithm with all the lift/gamma/gain tweaks in the HDR stream they can produce a pixel & colour accurate SDR version at the far end with no extra bandwidth required. Super-cool.

Canon DP-V3120 4k/UHD/HDR grading monitor

We sold a few of the earlier gen Canon DP-V3010 4k displays and although they were good 4k displays their HDR abilities were more limited than the X300 – in fact today they would be an equivalent to a £3.5k Eizo CG319X.
The new monitor uses the same Panasonic panel & backlight as the Eizo and Sony, but in this case it is a single-layer IPS which means the blacks are probably not as good as the CG3145 and the X310. I’d have to test that when we can our hands on one.
  • 2,000Cdm-2 max light output – probably because it’s only a single layer, they’re letting all the light through. Not sure why this is a benefit as nobody (Netflix, Fox, Warners) are specifying 2,000Cdm-2 deliverables and the next bump to DolbyVision will be to 4,000Cdm-2 so this seems to be neither fish nor fowl – much like the Flanders 3,000Cdm-2 monitor.
  • Tone-mapped false colour display – this is very nice; As far as I could tell this is nerly as good as Leader’s “CineZone” display but available in the monitor.
  • Same set of inputs as the new Eizo
  • Sub £20k price tag

ColourSpaceCMS colour management and LUT building software.

We sometimes sell a LightSpace license with Klein colour probes and I tend to then provide a day’s training (doing it next week at a customer's).
  • Much more modern interface – lots of people complain that LightSpace looks a bit 1990s and things like loading LUTs and talking to patch generators takes a few mouse clicks rather than being auto-detected. ColourSpace seems to address all of this. I've never found this to be an issue; if you've spent thousands on a probe and software you should really get familiar with it.
  • Profiling engine can run whilst you are manipulating LUTs – very cool; will go some way to addressing the two hours of thumb-twiddling I have to do whilst profiling a display.
  • Multiple probe support – you can be profiling two displays at a time; but with probes costing >£6k I wonder who will use this?! Monitor manufacturers at their factory, probably.
  • Price – near-free upgrade from LightSpace depending on age of license.
We never really offer LightSpace as a product by itself; always as part of a package and as part of the colourimetry training day.

Leader LV5900 – 8K test and measurement
  • 8K (so quad 12G) version of the LV5600/LV7600 series we sell.
  • Price – silly money! >£50k basic

AJA Image Analyser – HD/UHD/4K/HDR test and measurement

They’ve been selling this for a year as a competitor to the Leader but I don’t know it’s HDR abilities.
  • Quad-12G – now can operate as a 4 x 4K machine; perhaps an OB that is sourcing Slog3 cameras and delivering both HLG and rec.709 would find this udeful?
  • Price - £16k (so cheaper than an HDR/4K optioned Leader)
Also – all the Hi5-4K+ and associated boxes now support Dolby metadata passthrough so no more hooking up the USB control to force displays to switch between rec.709/PQ/HLG. Nice.

The Bryant Unlimited cable manufacturer's meal - the highlight of my professional year!

Saturday, August 03, 2019

Calibrating the Calibrator - Colour management with Eizo CG319X

I've spent a lot of time demo'ing these monitors recently and the thing that tickles customers the most is correlating the internal sensor to an external probe.


Saturday, April 20, 2019

Electronics, disasterous career choices and good techy YouTubers...

The last few months have been a bit of an education for me; I changed jobs twice and kinda wished I hadn't - neither has been ideal. However, I wound up with six weeks with not much to do (I did a few days of freelance colour work) but I took the opportunity to finish off my home fixing bench;

After this I resorted to my usual cathartic activity of building a hand-held games console based around a RasPi and fitted into the dead carcass of an old Gameboy/Gamegear etc. I didn't make any videos of this project (unlike the Gamegear from last year;

BUT, back to the most recent build; I was really pleased how it worked out, probably the most tidy one I've done to date. I also implemented a proper shut-down script so the power button doesn't just crash the Pi (and I monitor the LiPo's voltage to avoid the system crashing that way too).

The other thing I took to whilst off was to start learning the Python programming language - if you're looking to get back up to speed with coding Python seems to cover a lot of the principles of modern scripting languages - the thing that has blown me away the most so far is the list data type - a list can have different data types within it! Perhaps all modern languages have this, but my degree in Maths and Programming in the mid-eighties did not prepare me for such things!
Can I recommend Jamie Chan's book "Learn Python in one day and learn it well" - as someone who still has a bit of C and VB experience it has bee good for me.

I have also been catching up on my favourite electronics YouTubers;
Louis Rossman - Apple repair guy and the best example of surface-mount rework and diagnostics you'll see.
Big Clive - more focussed on big volts and tearing down badly made power electronics!
Great Scott! My kind of small project builds with something of a focus on Arduino
A brother broadcast engineer who fixes stuff
The Post Apocalyptic Inventor - motors and generators are the emphasis of his builds
Dave Jones of the eevBlog is a design engineer who seems to know everything about electronics; really engaging style too.

So, not sure how 2019 is going to play out - one thing I have realised is that my plans of giving up all this broadcast engineering nonsense are perhaps closer than I thought; maybe the teaching PGCE is even closer than I thought...