Multicast addresses in IP

I thought I knew TCP & UDP/IP but I was reminded this week about the 224.0.0.0/4 multicast subnet. If you're ever in a position where you need to identify a device's IP address (even on a different subnet, but the same LAN segment) you can PING 224.0.0.1 and everything on the segment will respond to the PING (firewall settings permitting).

 

So, if I set my machine's IP address to 192.168.1.220 on a 10.100.100.x network and then PING the multicast address;

You can see that all the machines on the 10.100.100.0/8 network respond.

This comes in very useful with Amulet DXiP cards which you configure over a web interface. Our demo kit came back from a customer who had forgotten what they had hard-set the cards' IP addresses to and this technique was a life-saver.

Thanks for reminding me of this Graham and Don Poves!

Wikipedia article on multicast IP

Some more training notes

Video Measurement - Principals (4 days)

Course Aim The aim of the course is to provide grounding in video fundamentals, compression and picture quality analysis for staff who work with video processing, detection and vision systems.

Course Structure 

• Day 1 - TV Fundamentals; Scanning and Sampling, Colour Systems, Analogue Composite Coding - notes
• Day 2 - TV Fundamentals; Digital Component Coding, Conversion of Film to Television, High Definition - notes
• Day 3 - Compression; DCT principles, Intra-Frame vs Inter-Frame Encoding, blocks and macroblocks etc. Video Tape Recording; Magnetic recording principles, rotary recording, Simple VT maintenance - morning notes, afternoon notes
• Day 4 - Television Measurements; Analogue, Digital, Picture Quality Analysis; Analogue picture impairments, digital picture impairments, compression, TV Displays; CRT, LCD and Plasma displays. Problems with LCD and Plasma, Projection systems - morning notes, afternoon notes

Cladding vs Core Alignment fusion splicers

For seven years we've been using Tritec Fase II fusion splicers; we have two kits composing the splicers themselves (camera or microscope inspection), clevers and finishing ovens for the splice-protectors. If you're in the business of bespoke fibre then fusion splicing really is the only way to go as you get superior performance in termination and you can base infrastructure entirely on loose-tube multi-core cable (tight-buffered cable is really only suitable for use within cabinets or at most between cabinets - it isn't man enough for running in voids and risers).

Anyway, the Tritecs have been solid workhorses clocking up many thousands of terminations between them and we've been entirely happy. In 2004 and then again in 2007 when we upgraded them they were the best sub £10k machines.

The only thing you could criticise them for is that they are "cladding alignment splicers" - they rely on the diameter of the cladding being correct (125 microns, fact fans!) and the core being correctly positioned within the fibre. The guys at Tritec tell me this is a non-problem as contemporary fibre optic stock is always spot on - ten years ago, not so much, but for now it's a problem that's solved and it is fair to say we have seen very little badly made fibre since we started; and that's many hundreds of kilometers of fibre cable!

 

The other side of the coin is the newer style of fibre machines called "core alignment splicers" where two cameras set at 90 degrees examine the cleaved ends of the fibres  and the software dynamically aligned the ends and dried the splicing arc. The machine is then able to illuminate the join and make an estimation of the loss across the join. Fujikoura were the pioneers in this field in the mid-noughties with machines like the FSM-series costing more than £30k - clearly you'd have to do a lot of fibre work to pay off one of those! Guys who use both types a lot reckon that core-alignment machines allow you to work about twice as fast as the machine produces a much greater consistency of good splices and doesn't rely on the operator to maintain precise splice measurements. Ask any wireman about the 'fibre-blindness' that sets in around 15:00 each day; you just need to walk away and forget about squinting down a microscope for an hour or so; these are very small measurements after all!

So, we've just splashed out on an INNO IFS-10 which gets really good crits when compared to the current FSM-60 machine from Fujikura. We're going to take it on a big job we're just starting and so I'll get a good feel for it.

Here is an excellent "torture test" video of the machine in action.

Amulet - they fixed OS-X's Temporal Dithering issue

As mentioned in a previous post temporal dithering on OS-X has proved troublesome with Amulet (and in fact it bedevils all KVM-over-IP systems). The guys at Amulet have written a Kernel Extension that stops the card turning on temporal dithering. James, their engineer, explained to me that it's a different technique between nVidia and Radeon, but they've got it licked;

 

 

kexstat is a utility to show which Kernel Extensions are loaded. Here I've grep'ed the output to exclude all the Apple ones. You can see the Amulet one at 0x2000

The proof of the pudding is that now all the MacPro clients on this particular Amulet system look splendid; even full-screen replay of 1080P material.

New podcast - RS232, fifty years and still going!

Hugh and I go into the details of RS232C and how it is still used in broadcast engineering for configuration and test. Find it on iTunes, vanilla RSS, YouTube or the show notes website.

Getting cheap/unsupported laser printers working on OS-X

Got a Dell, Samsung or Xerox printer where the manufacturer has dropped support AND it was too cheap to have a full Post Script implementation? Whereas Windows seems to support a very broad range of budget printers natively OS-X is more picky when it comes to PCL-models.

So - this saved us at the workshop; http://guigo.us/mac/splix/

Miranda, Grass Valley and good-old GPI tallies

I never realised that lots of manufacturers use ACOS protocol to send tally and UMD-names between vision mixers, multi-viewers and routers. I assumed that big switchers still used GPI closures for tallies but when I got to a customer's site to make a GVG Kayak mixer talk to a Miranda Kaleido multi-viewer I couldn't find the RS422 port on the back of the Miranda; turns out it's an option!

So - back to the good old dry-GPI (i.e. relay closure) tallies.








After a couple of false starts here is the cable used to connect the GVG to the multiviewer.

The next thing is to associate the appropriate GPI ins with the video inputs on the multi-viewer; this is X-Edit, Miranda's network config tool. Once you've dragged the GPIs to the source lines you have to go into the layout tool and associate the UMD red-light-up (it the RHS of the UMD definition) with the GPI event - you can set as many or as few of the virtual displays to activate.

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).

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. 

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.

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.

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.

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!)

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.

Crystal Vision audio pinouts

RS232 - fifty years old!

It was 1962 that the first draft of the RS232 standard for serial communications was published. 

I used to have a good side-line in making null-modem RS232 cables for my colleague who were often confused by why you even need a cross-over cable. The thing to remember about RS232C is that it was only ever intended as a means of connecting dumb terminals (think VT100) to modems.

The EIA RS232C (1969) standard defines two types of equipment:

• DCE - Data Communicating Equipment; typically a modem.
• DTE - Data Terminal Equipment; typically a dumb-terminal or PC (in the last thirty years!)

Only one style of connector is defined - the 25-pin D-type (no 9-pins or RJ45s!) and the sex of the connector reflects DTE or DCE (male for DTE, female for DCE) - that's it; everything else is a departure from the standard. So, the original intention was:

terminal <-> modem <- phone or leased line -> modem <-> mainframe

or, put another way:

DTE <-RS232-> DCE <- phone or leased line -> DCE <-RS232-> DTE

And that's it - it wasn't intended for management ports on disk arrays or ethernet switches, just modem/computer connectivity. Once you've grasped that fact you get an understanding of what some of the pins (used to be!) used for and why you need null-modem adapters/cables sometimes.

DTE (P.C.) <-RS232-> null modem cable/adapter <-RS232-> DTE

So it's probably worth looking at the pinouts for RS232, 

There's an awful lot in there! All the signalling lines that allow the modem to tell the terminal that it's picked up the 'phone line and detected a carrier or is getting a ring signal (RI - ring indicator) are all largely historic now, but have to still be paid attention to in some circumstances. What the standard assumes is a 25-core cable, all pins wired pin-pin with a female end at the DTE (to connect to the terminal's male connector) and a male end at the DCE. Notice that the transmit pin on the DTE end connects to the receive pin on the DCE end (Tx - Rx) and vice versa. The same is true of all the handshaking pins (RTS; request to send - CTS; clear to send).

So, if you need to connect a DTE to a DTE (PC to PC or PC to anything else that regards itself as a DTE - has a male connector) you need a cable that does the cross-over for you, a null-modem cable.

At this point it's worth talking about handshaking; if you have a modem talking over a slow line (and in the 1960s that would have been 110 baud; some people can type faster than that!) you need a mechanism of first ensuring the link is up (DSR; Data Set Ready and DTR; Data Terminal Ready) and then the flow of data is controlled (RTS; Ready to Send, CTS; Clear to Send). BUT, spin forward thirty years and you're using RS232 for PC-PC or other management functionality and the flow control needs to be either 'spoofed' by the cross-over cable OR it's probably being done by the software using one of several RS232 flow-control protocols. The most common if these is XON/XOFF and uses two special character to pause and resume transmission;

If you look in your Windows device manager for a port's settings you can see;

 So with all this in mind here are the pinouts for a null-modem cable; in fact there are two you can make - a three-wire (use a piece of FST - useful if all you've got is an audio tieline!) or a six-wire (which takes the hardware handshaking pins through) - send it down a cat5 line! In the case of the three-wire the handshaking lines are looped back on their equivalents at each end so that hardware flow control never stops the link.

So the final thing is probably to give the pinouts for a 9-pin -> 9-pin (which would by definition be female to female) null modem cable for RS232C DTE-DTE cable;

Blackmagic's new digital 'cinema' camera

In the same way that the Red One seemed to break the mold of digital cinematography three years ago the interesting development at the moment is the Blackmagic camera shown at NAB this year. It has a 2.5k sensor and supposedly 13-stops of range (that's 78dBs if you're a video person!). Anyhow - I look forward to hearing from anyone who has used it in a non-Blackmagic funded film!

So - here is an article (admittedly from BM) that has some sample footage; 12-bit RAW DNG files (they are logarithmic - that's how you capture 13-stops of dynamic range in only 12-bits!). I downloaded a sequence and had a crack at grading a frame to what I thought looked nice (colourist friends may well disagree!);

The untouched frame;

What I think looks nice;

and some detail to see how much resolution is there;

Avid Knowledge Base XMON Cable Specifications

When building a custom XMON cable what guidelines should be followed? Here are the general specifications for the XMON cable. Note that 24m is the maximum recommended cable run. Beyond this distance some signal degradation may be noticeable (especially talkback and headphone quality). 

• Belden 9505 equivalent cable, 24 gauge, with sets of 5 twisted pairs. 
• Stranded tinned copper conductor 
• Twisted pairs - Only 5 pairs of cables are used: Signal pairs are 1 & 9, 2 & 10, 5 & 13, 6 & 14, 8 & 15
• Cores cabled under Aluminum/Mylar foil 
• Connectors are 15-pin D(m) 

I always resort to using the pre-made Avid cable as I have NEVER got this to work as a homebrew!

Imre Lakatos and a definition of pseudoscience

I did several philosophy of science courses on my degree and although everybody knows about Sir Karl Popper and Thomas Kuhn less people know about Lakatos; He had a lot to say about pseudoscience - things that look a bit like science (to gain respectability for their ideas?) but fundamentally differ from real scientific theories.

According to the demarcation criterion of pseudoscience originally proposed by Lakatos, a theory is pseudoscientific if it fails to make any novel predictions of previously unknown phenomena, in contrast with scientific theories, which predict novel fact(s).  Progressive scientific theories are those which have their novel facts confirmed and degenerate scientific theories are those whose predictions of novel facts are refuted. Lakatos's own key examples of pseudoscience were Ptolemaic astronomy, Immanuel Velikovsky's planetary cosmogony, Freudian psychoanalysis, 20th century Soviet Marxism, Lysenko's biology, Niels Bohr's Quantum Mechanics post-1924, astrology, psychiatry, sociology, neoclassical economics, and Darwin's theory.

There is a very good article on the LSE's website including a recording from the early seventies where he explains the difference between science and pseudoscience.

Beyerdynamic DT-250 series headsets

I'm just prep'ing a few Beyerdynamic DT250 headsets for a customer - football club we work with a lot! Their commentary guys love these headsets and the quality/comfort is hard to beat for either pitch-side or commentary booth use. They come with a proprietary connector and being German it's all beautifully manufactured.

This customer sometimes uses these with portable Glensound ISDN codecs (reporter-type mobile packs) and sometimes with Yamaha audio mixers and so they need both the 5-pin XLR option and the 3-pin XLR/1/4" stereo jack cable. Since removing the rigged cable requires a screwdriver and is fiddly I normally ship these with the 5-pin cable and make up a breakout;

Alternatively you can order the two different cable options, if you can get your colleagues in Sales to pay attention!