Friday, September 28, 2012

Windows HD .WTV files; what can you do with them?!

I record off-air TV using Windows Media Centre. Those channels that broadcast in HD do so over the DVB-T2 standard, and in the UK at the moment that means H.264 in the transport stream. Media Centre wraps them as .WTV file which are almost unusable (other than playing back). You can't even re-wrap them to the earlier .dvr-ms format that other PVRs use (and is more convertible)

But, it turns out that the new version of Handbrake can handle them and convert them to vanilla H.264 with lots of pre-sets for iPad and other platform. Then you can use Quicktime to trim them (remove ad-breaks etc).

Thursday, September 27, 2012

Some interesting domestic electronic fixes

Fridge/Freezer earthing conundrum

I've had my Miele fridge for maybe six years and it's one of those frost-free models; I assume an extractor fan maintains negative pressure inside so that moist air that has entered when you open it gets drawn out. About three years ago (after I'd re-arranged some of the mains in the kitchen) it started icing up every few months like an old-style freezer. Of course it was outside it's warrantee so we lived with it. Around eighteen months ago whilst cleaning behind it I noticed the mains cord had been tugged and the earth was disconnected. Of course I re-ended the cable but since then the freezer has stopped icing up.
I've searched online for a schematic for this model to see if I can figure out what is going on. I'm reluctant to disconnect the earth to prove it, but I'm left wondering (and no other engineer I've mentioned it to can give me an answer) why the anti-frost mechanism didn't work without the safety earth? I stuck the freezer on my trusty Martindale 2100 PAT tester and it was fine; no excessive residual earth current and all isolation good; even at 8A.

When is a micro-switch not a switch?

My Valiant combination boiler has the usual configuration of a butterfly valve that routes hot water to either the taps or the heating pump. There is a micro-switch on the valve such that when you open the hot water tap the boiler is forced on (it's unlikely it was on heating the radiators exactly when you needed to wash your hands). The boiler is fifteen years old and I've replaced that micro-switch two or three times before. Earlier this year it seemed to have gone again yet removing the connections and testing for continuity when the valve opened showed the switch (seemed!) to be working. In the end I admitted defeat and got a heating guy in. He concluded the same as me and he 'phone the Valiant tech support line.

"Replace the micro-switch"

"No, no - it's not the switch, it buzzes out correctly when the valve closes"

"Never mind that, replace the switch"

Because it's a common model of boiler and the micro-switch goes often he had the kit in his van. Sure enough, he replaced the switch and the boiler starting working correctly. I was now beginning to doubt a lifetime of electronics knowledge! I got him the call the helpline back and the chap at the other end explained that it's not just a DC voltage that gets switched but the i2c data link! Yes, I was amazed; I can only assume it's part of a wider control system (maybe common across much more complicated boilers); but if there is any electrical noise or impedance on the switch data doesn't get back to the control board and the boiler CPU doesn't fire up the gas.

XBox 360 and failed DVD drive.

What would imagine would be the part most likely to fail in any kind of consumer device? The mechanical part that has a 50p laser diode AKA the DVD drive. Given that it has two connection - SATA and power it should be a user-serviceable part and given you can buy them from eBay and spare parts suppliers home tinkerers like me should be able to fix their XBoxes. But no, the XBox OS is keyed to the firmware serial number of the drive that is installed at the factory and if it sees another drive it not only refuses to read the disk, but it informs the XBox Live! (why the exclamation?) mothership and your account is banned for being a game-stealing pirate.
In the end you have to get the same model of DVD drive (there have been four revisions over the lifetime of the '360) and swap the board between drives so that your new mechanics have an old firmware. It worked for me. 

Wednesday, September 26, 2012

How to do RS422 properly on the big Blackmagic Universal Videohub?

A job we're working on at the moment needs a big 288x288 HD/SDi and RS422 router. Budget means that the Black Magic is the only one that can be considered and it's hard to argue with sub £100k - Probel, Quartz-Everts etc would all cost four times that amount and so we're trying to figure out how to cable this one nicely.
The issue is going to be with the RS422; video will dress nicely on the cable tray down each side of the cabinet but the remotes are presented on a proprietry connector in the centre of each card. The only way of connecting to this is via a pre-made breakout cable that in only a metre long. So, after a lot of thinking and measuring we've come up with a solution.
 So far I've not been able to locate this connector - anyone have any thoughts?!
 Chopped breakout cable to see what the colour code of the cores is.

Nice 1/2u high cat7 jackfield which we'll use (need a dozen of them) to run down the intermediate rackstrip at the rear of the matrix to allow proper RS422 breakout.

The colour code we've settled on for this router when it's being cabled on cat6.

Tuesday, September 25, 2012

Avocent HMX-series KVM-over-IP, a few notes

Although I'm a fan of Amulet Hotkey for sending 2 x DVI, USB & audio i/o over ethernet networks (and even slow connections; works over a domestic internet connection) we did fit an Avocent HMX system on a recent job. 
Unlike the Amulet where you can do remote admin of both the transmitters and the receivers (referred to as Zero Clients) over a web interface with Avocent you have to use a serial connection (see my post about RS232 for making a null-modem cable!) with a slightly unusual comms setup.

The clever thing is that if you want to connect to a transmitter (the gadget that sits behind the server or workstation) you have to do it via a receiver that is logged onto that transmitter over the KVM-network. I suppose this allows you to administrate a very distant workstation's sender from where you are.
So - RS232 port (male, therefor a DTE, therefor a null-modem cable required) and you can see what you might not be getting any video from the remote computer.
What I discovered is that unless the EDID (or DDC if you're doing it over SVGA) profile matches the resolution of the sending machine you get no video! What is the point of that - the only reason to pass an EDID or DDC profile is to allow the graphics card to tell the system what resolution is being expect.
Anyhow - fixed that by logging onto the machine locally.

By the way - is there a decent PuTTY-like app for OS-X. Good job I keep Windows on my MacBook Pro for situations like this.

Wednesday, September 19, 2012

Fifteen years of HD displays in one morning!

I had to visit a new client to calibrate four different display devices and it struck me that they represented the gamut(!) of HD displays since the mid-90s. They didn't have an OLED display for me, but a Sony BVM-D24, a VuTrix Pro-24, an AutoCue G-series and a JVC D-ILA 2k projector.

The CIE 1931 chromaticity chart shows the extents of human vision with the RGB primaries mapped onto a pair of X-Y primaries that represent the colour content only and says nothing about the illumination of a colour. In the centre of the triangle is an "equal mix" of red, green and blue which is the very definition of white light. The various standards for the white-point used in different territories and applications is shown as a curved line. In TV pretty much the whole world now regards 6500k (actually, 6504k - had to be updated in the seventies when physicists realised they'd got Planck's constant wrong!). When I test myself I can only just discern the difference between 6500 and 6600k colour temperature.
Anyhow, metamerism aside (and that's another blog post!) you can't use the same probe to calibrate different display technologies. My venerable old CRT probe is no good for LCDs and vice versa (and that's before you consider plasma and OLED displays). That's why the £200 Huey-type probes you can buy on Tottenham Court Road are worse than useless.

  • Sony BVM-D24 - Old faithful, the HD display we've all been using forever. I'm starting to notice that the '24s I see now are in the autumn of their tube's lives. They are still the gold-standard for colour and unless the EHT is wrong or the tube is really knackered it's a nice and easy to job to get a D24 correct in the blacks and the whites and generally they track splendidly. As ever they look best when the white point is set below 100Cd/m2
  • VuTrix Pro-24 - These could be could be considered first generation broadcast LCDs as they are rear-illuminated with fluorescent strips. This particular one had to be really wound out from it's factory defaults to get it even near standard. They also have no sensible way of setting the colour in dark areas of the picture ("bias" on a Sony monitor). These have poor off-axis black performance as well.
  • AutoCue G-series - This was a new monitor, the G-series are their best ones with LED backlit LCD panel and a really nice look. Easy to get it looking correct from a colour point of view and it's factory preset was pretty darn close to illuminant-D. They must have some sort of fancy dichroic glass on the front because the off-axis performance is pretty good.
  • JVC D-ILA projector - because I don't have a spectral-radiometer (a wide band colour analyser), only photometers (colour probes that rely on having the same metameristic failure as the the device being analysed) I have to eye-match projectors to a know calibrated LCD or CRT. This is the bit of the job I like the best. Since I spent a decent amount of the nineties racking studios cameras I'm used to colour matching. I don't have a good colour memory (I'm always surprised how milky D6500 white is compared to what I've remembered).

Once I've got the probe happy with the light coming from the front of each display I do an eye-match as a final tweak. BBC test-card F is perfect for this as it has lots of grey-scale and real pictures. It's always nice to give Carole an outing; she's the person who's been on TV the most in the whole world, ever!

You can see here the monitor on the floor is a bit redder in the whites than the projector; since I'd got the monitor correct I eye-matched the projector as best I could; but it's always a struggle because different display technologies just look different because they make colour in different way.

Friday, September 14, 2012

What I spotted at IBC 2012

I had a couple of days in Amsterdam at IBC (the TV industry's European trade show); I talked to lots of people and had a splendid night out with Bryant Broadcast (my main cable supplier) at the Braziliaans grill restaurant.

Anyway; the only thing that really grabbed my attention was the updated NewTek Tricaster - the model 8000. The really clever additions are;

  • Automation; mixer tasks can be grouped into macros
  • Control of outboard routers (essentially expanding the number of HD/SDi inputs)
  • Eight re-entrant MEs
  • A motion tracker (yes, in a studio vision switcher!)
  • Hot-spots that the talent can activate by their actions - think the weatherman being able to reach out and "pull" in his next map.
  • Up to four status monitors
  • A bunch of social media exports ("send that clip to Facebook now!)

Watch the video (Kiki features, as ever!)

Saturday, September 01, 2012

Engineer's Bench - new podcast "Custom Hardware 1: Electronics and Arduino"

Hugh and Phil talk about the need for custom made boxes and panels. They talk about the metalwork as well as circuit details used and wind up with a review of the Arduino platform

Find it on iTunes, vanilla RSS, YouTube or the show notes website.