Saturday, December 26, 2015

Extending wireless networks; some gotchas

Visiting the family over Christmas and of course there are the tech-support duties. One of which was making a wireless network extend further through an old house with very thick walls. In the small amount of time I had there wasn't the option of running network cables to some strategic points where additional WiFi access points could be installed so I invested in a couple of Netgear wireless extenders
I've used these before and been impressed; fast throughput and lots of features. They are proper NAT routers and you can use them as firewalls between ethernet network segments or extend an existing wireless network. In that mode (and it's a small switch that sets that mode) the ethernet ports become wired outlets for the WiFi network; intended for set-top boxes that can't be connected via a cable. They can turn a USB drive into a NAS drive and all this for less than twenty quid!
The only downside is that they have a single radio and so can only repeat a network on the channel that it arrives as. In a relatively WiFi-free environment you'd think this wouldn't be a problem, but I didn't figure on how rubbish the provided BT HomeHub 3 is! 

Since they have a flip-out antenna I figured I'd place one downstairs and one upstairs as close as possible to the room with the aDSL router and see how I got on. 

  • It is a cheap, plastic, single-board gadget
  • It has no external antenna or even socket for one
  • You have to use it as the BT mothership monitors for their own secret sauce
What I discovered after two days of frustration is that it is entirely intolerant of other devices sharing it's channel. The Netgears can only repeat on the channel they receive on and so I was off to a non-starter. I would work for a few hours an then both of the Netgears would drop off the network and a round of re-booting (and half an hour for them to all settle down again) told me that this was not a reliable configuration for non-technical users.

So - after a bit of chin-scratching I came to this configuration;
  • Netgear no.1 is wired to the BT hub and set for Access Point mode; it's re-serving the connection with a new IP range and (crucially) a new WiFi channel some distance from the BT hub.
  • Netgear no.2 is set for wireless extender mode and is located at a mid-point in the house repeating the signal from no.1
This has been stable for more than a day now (I've insisted that my boys use the furthest repeated network) with only minimal speed loss (typ. 8 mbits-1 against 10mbits-1 at the BT) so I'm going to run away and hope!

Saturday, December 19, 2015

Colourists are the last people who should have a say on monitors!

I was recently in a decent grading room - Dolby PRM 4220 monitor and I was demo'ing a Boland BVB25 OLED display. The demo unit had come back from a try-out at another customer's and I hadn't had a chance to check it's calibration (Rec.709, illuminant-D yada yada...) and so I grabbed the colour probe kit and calibrated it whilst chatting to the engineer and colourist. Once done I looped it off the Dolby to see how they compared and they were quite different! The Dolby was sat-up, over-saturated and a bit red-in-the-whites. The conversation went;

Colourist:"It doesn't match my Dolby",
Me:"…you just watched me calibrate the monitor for Rec.709",
Colourist:"It's wrong",
Me: "Is the Dolby set for Rec.709?",
Colourist: "No, I feel that when I export Quicktimes for customer approval how I have the monitor set now matches what they see better"
 I also have the same convesation about black levels endlessly. An online editor had a go at me because I'd left his monitor "too crushed in the blacks" - here is a frame from his timeline;

It is a continuous battle to persuade people that monitor calibration is NEVER a matter of opinion, rather it is defined by measurable technical standards and when I calibrate a display it is correct. Your material may well not look how you want it, but don't corrupt your monitoring pathway to make your project look good.
Often I'll ask the colourist what standard they want the monitor calibrated for; it's rare that they know what I'm talking about, but they'll often venture an opinion that their display is currently "too cool" or something (quite how they know without a reference I'm not sure?).
I suppose a lot of this is down to the fact that colourists are people who have to be very confident in their ability and are paid handsomely for what they do. However, they have to realise that their mojo doen't extend to how their monitors are set up. When I demo a monitor my heart sinks when someone says "we'd better let the colourist have their say" - monitoring is not about creative magic, it's about compliance.
This December I've calibrated over thirty customer broadcast displays; I've been there/seen that more than you!

Thursday, December 17, 2015

Gotchas with updating firmware over RS232

I've recently been upgrading Boland BVB25 OLED monitors over their RS232 serial ports; aside from needing a USB/serial adaptor (I use the Keyspan which mimics an old PC serial UART) you also need a null-modem cable (i.e. where Tx and Rx are swapped over). You can tell if a null-modem cable is required by the sex of the connector on the back of the equipment. A 25-way or 9-way D(male) indicates a DTE ("Data Terminal Equipment" - a PC or terminal) and a female connector a DCE ("Data Communication Equipment") - a modem in RS232 speak. So, if the gear is a DTE then you need a F-F cable and by definition is has to be a cross-over (AKA "null modem" cable. I've banged on about this in the past, and there is also the consideration of handshaking; does you gear/app need the hardware pins (DSR, DTR, DCD etc) or does it use software flow-control (XModem etc). Hugh and I did a podcast on the subject if you need to brush up on your serial comms.
Anyway, because RS232 is such a low level way of doing things it's often the case that the receiving UART in the equipment can get direct memory access before the OS has loaded and you may need to jump through some hoops to get the thing into "serial update mode". In the case of the Boland monitors we sell it's necessary to have the updater software running and looking for comms before you do a power-down reset of the monitor; and not just power-down - tug the power cord, and then within a second or so of re-applying the power the monitor will start talking and appear dead from it's front panel but stuff is going on.

This kind of three-finger tomfoolery really reaches a zenith when you're upgrading the Linux SOC kernal on Amulet DXiP cards!

Thursday, December 10, 2015

4k and UHD cabling and signal standards

I've had to dig into signal transport for 4k/UHD over the last week or so. Essentially I have a test-signal generator (SRI Visualizer TG100) running at a maximum raster of 4096x2160 at a maximum of 25 progressive frames/sec (and only 4:2:2 colour sampling; Y, Cr, Cb) with a 6G single-link output (so really 4 x 1.5G links) and HDMI 1.4 (so the same raster as the SDi). The monitors are the 24" and 30" Canon IPS 4k native monitors.
The Canon monitors will take quad-link HD/SDi and (in the case of the 24") HDMI. So, feeding the SRI single-link into a Blackmagic 4k multiplex (to produce quad-link) and then into the Canon produces four quads in the wrong colour-space!

 For an insight into what the multiplex is doing it's worth looking at the two standards for quad-link SDi. Put aside if it's 4 x 1.5G or 4 x 3G (that allows an increase to 50 or 60P OR 4:4:4 colour). But, in this case we're de-mux'ing a 6G to 4 x 1.5G signals. 

The original 4k-over-four-BNCs standard

The more recent standard; each link looks like an HD version

Clearly the converter is producing 2SI but the Canon expects SD quad-link. In fact the guys at Canon tell me they have a firmware update early in 2016 to address this. The other error is that the Canon has mistaken the 4:2:2 video as RGB - but it has at least got the raster correct.
So, what to do? Well, by throwing in another converter and taking the HDMI out of the SRI means the BM mux will get an older SD quad-link input;

This produced what we need; clearly HDMI has not concept of mutliplexed pixels and so we're now fully in SD quad-link;

tugging BNC no.4 shows the monitor is now in quad mode

The monitor gets it all right

The other thing that you have to pay attention to in "True 4k" displays (for the film snobs!) is that feeding 3840x2160 signal into a 4096x2160 monitor and letting the monitor scale-up to fill the line risks killing your resolution;
The aliasing should only the present in the top-most block, the other alias frequencies you can see here are due to my iPhone's camera!

Some very strange aliasing when a 3840-pixel line is mapped to 4096 pixels

As ever with display devices, pixel-pixel (native resolution) is always preferred

Friday, December 04, 2015

Barnfind integration with third party control panels

Barnfind are one of the products I'm responsible for at Root6 and I love them for their forward looking attitude and the fact they embrace open standards; if you see an SFP hole or a BNC connector you know that it will work with any other manufacturers (unlike Evertz who re-define the standard and put an X at the start of the product name!).

So - the BarnOne BTF1-07 is the chassis I have in my demo kit and at IBC this year Wiggo and the guys were showing a much wider set of third party control panels they have integrated to work with their cross-point router. So, to make our demo more compelling I bought a BlackMagic VideoHub Smart control panel and set about making it talk to the BarnOne.

Since I have to rock-up at customers' facilities to show this gear I figured it's daft to rely on their networks and so I've included a TP-Link travel router to dish out IP addresses to the panel and the BarnFind; it also allows you to use a wireless laptop to then run the demo. These little gadgets have single WAN and LAN facing ports but rather splendidly the BlackMagic panel has a little ethernet hub inside so you can loop the network connection to the Barnfind. 
This screen-grab is from BarnStudio - the config/control software for Barnfind products. It has a discovery protocol so it can find any chassis on the same LAN segment. However - I discovered a couple of gotchas;

  • When upgrading the chassis you can either attach a USB stick to the front and the embedded Linux machine will grab the image OR you can use BarnStudio. Initially I couldn't get either to work! 
  • Barnstudio just instructs the Linux machine to do an apt-get (or similar) and so it has to be able to see out to the internet; connect the WAN-side of the little router to the workshop network!
  • If you do the USB route then the installer checks the signature on the package; again, it needs to get out to the web to verify the cryptographic signature.
  • The Blackmagic panel does not have any host-discovery protocol built in and so it seemed only sensible to set the router to always dish out the same MAC/IP address combinations by using the DCHP reserved assignment page in the router. Then assign those number in the BlackMagic config software.
After that it really is very simple - you set the virtual buttons to be whatever sources and destinations you want. You can even reserve some to be macros (which are then just a list of route assignments) - in fact that is how you would do duplex signals; Ethernet etc. You have to assign both the in and out of each SFP (Tx and Rx). You don't have to have sequential sources or destinations and I can't honestly see how they could have made it any better!

So - with BNCs 17 & 18 on the front of the Barnfind defined as 3G HD/SDi video in and out and these button assignments on the BM panel I've got proper router control. These forty-button panels will be very useful for controlling all the synchronous broadcast signals (HD/SDi, HDMI, MADI etc.) and asynchronous data signals (Ethernet, fibre-channel etc) running through a Barnfind router (and then out and over CWDM fibre?).

The only criticism is that the software matrix takes a second or so to update after panel changes are made; but I can't honestly see when that would be an issue - this software matrix is  tool for the engineer, not the operator.

As an aside they have recently published a very complete integration guide with lots of examples and advice.

Wednesday, November 04, 2015

Colour of the wall and lights in grading rooms

In the last year or so a lot of my time seems to have been taken up with getting monitors and other display devices to show the correct colours for film and TV. However, as with all other areas, context is everything and the colour of the wall behind the monitor (and the colour of the light illuminating the wall) are as important as the calibration of the monitor.

Picture from Robin at Wire Broadcast - Grading Suite at Envy
Nobody has perfect colour memory (remind any colourists you know!) and if the rear wall of your grading room is slightly yellow your eyes will adjust to that and you'll tend to grade pictures as if yellow is white and in truth your pictures will be missing blue. So - what's the standard? ISO 3664:2009 specifies "N8" as the neutral grey for accurate colour environments. Essentially you want a paint that favours no reflected colours. You can spend big bucks buying the approved paint from eCinema or RPimaging but you'll wind up spending many hundreds of pounds for a few cans of paint and it isn't really necessary.  I've had splendid results with Crown Plain Grey 5574 Matt Emulsion. In fact ColorTechnics specify that paint for use with their VeriVide D65 “Artificial Daylight” CIE daytime illuminants fluorescent tubes.

Having said that I've never bought the approved tubes, preferring to go to the electrical wholesaler and pick up normal shop-type ones. It turns out that the pet-store industry favours D6500 colour tubes as the light output stretches down into the UV end of the spectrum (sub 300nm wavelength) which animals respond well to. One thing that I have been told is that there is small variance between batches and so it's best to overbuy so that once you've got the holders and baffles fitted you should visually (or using a photometer) make sure the colours are matched. It takes only around 100k of difference for you to be able to spot it immediately and so it's not surprising the manufacturing tolerances are not good enough for TV.

So - wall painted, florescent tubes fitted; what next - well, since you're looking for around 15-20% of the light output of the monitor as a surround (so around 20Cd/m2 from the wall) you need a way to control the brightness of the tubes. You could dim them but there is always the risk of the switching waveform breaking through onto your audio system AND tubes change colour as they are dim'ed (particularly as they age) and so the best thing is to fit mechanical baffles to them; Bryant do some excellent ones - but throw away the tubes as the ones supplied at 6000k colour temperature; a tad too red for grading suites.

There are a few other things people obsess about when setting up grading rooms;
  1. The Tek WFM601 used to come with an option for a white display (quite a lot more money IIRC) so that the colourists eye wouldn't be drawn by the green phosphors!
  2. Computer monitors - you should run them dimmer than the 200Cd/m2 peak that most people have.
I'd agree with the second point, but the first one seems unnecessarily picky.

Of course, the biggest offense to anyone who cares about colour fidelity in the film and TV world are these things, Philips Ambilight TVs!


Thursday, October 29, 2015

UHD-TV test material; how I'm going to demo monitors

After all the monkeying around with the Canon monitors last week I decided I need a decent variety of clips to show off UHD displays to the best of their ability. For some reason customers are not satisfied with just seeing test signals?!
So - although I have the TG-100 for uncompressed 4k test signals (the Visualiser really shows all you need to know!) and I can show:
  • Resolution
  • Colour Space
  • Temporal performance
  • Dynamic Range
So, I went looking for some well shot UHD footage at the TV 4k raster of 3840x2160 (I know, all you DCI-snobs, "true" (sic) 4k is 4096x2160). The Harmonics site has some nice short uncompressed YUV-planar format videos; - But don't expect your laptop to be able to play these guys! At 12GBits-1 they are monsters and so for ease of use you may want to compress them down to a more manageable 500MBits-1 (or so) using GLYUVPlay which can be found at Henryk Richter's site. In video coding research, standalone implementation and testing of video codecs often involves the use of raw YUV streams. Since these streams can be parsed and generated by very simple means, raw YUV files are very common in video codec standardization and development. 

I have made the H.264 variants and you can find them on my Google Drive folder.

Friday, October 23, 2015

So it's time to change ISP (again!)

So it looks like TalkTalk have had their customers' database exfiltrated and it seems they have done everything wrong! It's a shame as I've found them to be a fine ISP (MUCH better than Virgin) with good speeds and impressive uptime. They haven't bugged me endlessly with the TV and mobile up-sell and the bill has remains consistently ~£15 month-1 less than Virgin ever was.

So, having watched with a mixture of annoyance and amusement here are a few thoughts; 
  1. Don't claim that "we take customer account security extremely seriously" after a breach; behave like you believed it before the hack,
  2. Don't hide behind the claim that "...we have been suffering a sustained attack" - all ISPs (or any big internet-property) is under constant DDoS and other assault; it's no excuse today.
  3. Don't tell customers to go and update their user passwords and then have a broken website for twelve (and counting!) hours afterwards,
  4. Hash your customer database with a reliable method (even MD5!) and salt the hash - in 2015 this is now considered standard practice for people who "take security extremely seriously" (sic),
  5. Don't tell customers to "keep an eye on their bank accounts and credit card statements" - this is your fault, don't load the responsibility for the mess onto customers,
  6. Put data security and best practice ahead of sponsoring TV talent shows,
  7. Have a chief executive (who had the nerve to go on Newsnight) who actually knows how your customer database works - they're the CEO of an ISP for goodness sake!
So that's it; perhaps now ISPs will use results of proper pen-testing as marketing rather than the guff that passes for customer information currently in service provider adverts. If one company includes the word "bcrypt" on their website they'll get my business.

Thursday, October 22, 2015

Canon's 4k Native IPS television monitors

I had an excellent half day with Canon's UK imaging display guys to look at their DP-V series 4k native displays. To my shame I had assumed that they would be like the HP Dreamcolor or Eizo ColorEdge series monitors which are advertised as being suitable for film and TV work but as I've often said; " SDi BNC and a preset called Rec.709 does not a broadcast monitor make"!
In the case of those two manufacturers they assume that taking their print-prep graphics display and making it SDi capable is all that's needed; forget proper RGB linearity and a controlled white-point. In the case of the HP they still advertise it at 250Cd/m2 for white (four times what it should be - you can't grade with that) and every time I've had an Eizo to play with I've found the same. Even employing a LUT to tame something like that is a bad idea as having to take 250Cd/m2 down to a more sensible 80Cd/m2 means you've lost two stops (12dBs, two significant bits) of dynamic range; not what anyone wants.
So - native 4k displays using LED-backlit IPS-LCD and not OLED. Every display technology suffers issues and although I think the poor inherent RGB tracking of OLEDs is entirely addressable in a LUT (which is why I love the Boland BVB25 for colour-accurate TV work) OLEDs are noisy once you get very close to black thus limiting their dynamic range (fine for 10-bit TV work; but for 16-bit HDR film imagery, not so much - yet!). Canon has consequently chosen IPS-style LCDs (with a level-modulated LED backlight). The LED backlight is the same technology as that used in the Dolby PRM-4220 grading monitor which is how they achieve the high dynamic range with a possibility of >1000Cd/m2 for specular highlights in HDR 16-bit video. I got to see the originators of this technology, Brightside, back in 2005
So, proof of the pudding etc - I profiled the 24" edit suite variant and it was very close to the Rec.709 spec (the fact that I left LightSpace set for a 2.2 gamma whilst the monitor has a true BT.1886 gamma for HD rasters may be to blame). With 4k source material the results look great.

 I started at 2k to see how it did

 At 4k I can only manage 25 FPS at best!

Zooming in on the frequency grating shows aliasing, but only on the camera pics, I couldn't photograph it with my 10Mpix camera without catching aliases in the camera's OTF.

Getting closer gets a bit better, but to the eye the resolution is astounding
The Sarnoff ladies at true-4K

I profiled the display at 17-points so 5,000 measurements take around two hours with the Klein
Looks pretty good for greyscale performance, and I suspect if I set LightSpace's gamma correctly it would be better

The coloured dots are rec.709 and the big cube is the gamut of the display; it covers the colour space nicely.



Friday, October 02, 2015

The £50 Amazon Kindle Fire 7" tablet

I spanked £50 of birthday vouchers on one of the new cheapie Amazon Kindle Fire tablets - just the little 7" one - very similar spec to the current Google Nexus 7 tablet. 
It's very clear that they're selling it as a loss-leader on Amazon Prime and the Kindle Store etc. There is no way they can build a 7" Android tablet for around 10% of the cost of an iPad!

I've forced myself to put the 10" iPad aside for a couple of days and use this and for the most part I've been really impressed. Part of the exercise was also to get a bit more familiar with Android and although Amazon describe this as "Fire OS5 Bellini" but it's really Android 5 Lollipop with Amazon's skin. This is fine for the most part except for the fact that Amazon and Google don't get on and so you don't get the Google Play Store. There have been a couple of apps which aren't yet on the Amazon Store and so they aren't available on the Amazon tablets. Most significantly Dropbox - hmm, bit of a problem.
However - as a tablet OS it is nippy; apps launch quickly, the screen swipes and scrolls nicely and makes for a very nice experience. It's a lot lighter than the iPad at 300g and so is much nicer for reading in bed. The fit and finish is much like the Google tablets and considerably better than other sub-£100 "one-hung-lo" brand cheap Android tablets. It only comes with 8 gigs of memory, but they throw in a 32gig SD card (or they were for pre-orders) and since Android manages all of that it's really not an issue.

So far it works well with all the Bluetooth gadgets I've tried (a couple of speakers and a keyboard) and it hasn't dropped off any of the wireless networks I've attached it to (and I can't say that about the iPad). It has a much lower resolution screen than the iPad but I've only noticed that on the Facebook app.
In terms of resolution the camera is not great - I took a bunch of photos on a nice sunny day in London and they all look a bit like 'phone camera pictures from ten years ago!

Another area where it scores over iOS is that you can see the file system - USB cable (standard micro-B connector; you probably have several of them already - especially if you have a normal book-reading Kindle). It makes extracting photos or dropping MP3s, documents etc onto the device a doddle (can't do that on an iPad!). Another very cool (and non-Apple feature) is the profile selection from the lock-screen. On the subject of the lock-screen you get adverts (I've only seen books so far) but clearly this is where some of the economy comes from. 
So; top-right on the lock-screen you see icons with names. If you've added additional profiles multiple people can unlock the gadget and it gives you all your stuff; your Amazon accounts (Kindle books, Amazon music etc) as well as a new profile for email (POP3, MS Exchange, IMAP, Google etc). Again, not something Apple has ever been able to do.

So, Pros
  • Profiles
  • File System
  • Standard Connectors
  • PRICE!
  • No Google App Store
  • Screen resolution (only in some cases)
  • Camera resolution
BUT, 10% the price of an iPad! I'll probably root it and stick regular Android 5 Lollipop on it when I can an afternoon to spare. It's not quite an iPad but I could have ten of these things for the same price!

Tuesday, September 22, 2015

Fibre infrastructure and CWDM developments

The most interesting things I saw at IBC last week were not software updates or new 4k workflow tools (save us from "workflow tools"!) but some developments from our good friends at Barnfind
Their current CWDM products top-out at 18-wavelengths on a single fibre, and if you need to pack more signals (synchronous broadcast; HD/SDi, MADI, AES etc OR asynchronous data; ethernet, fibre-channel etc) onto a fibre then DWDM is the answer - with a big price tag!

  • They showed me a prototype of their "pre-mux" product which can take six wavelengths and multiplex them onto a single SFP-wavelength; essentially it reduces the channel spacing down to 1.6nm but the upshot is that it is entirely compatible with the existing product range. You can use your current SFPs, Optical de/multiplex and single-mode cabling. You wind up with 106 usable channels on a single fibre.
  • They also showed me Embryonix's ST2022 video encoder/decoder pair in SFP form; this allows you to use Barnfind as your video router in and out of an IP environment - I was blown away; a complete 2022-encoder with 10gig fibre i/o from a 3G source. 
  • Barnfind are also taking their router up to 12Gig for single-wire UHD-TV routing; this will allow much greater penetration into the 4K market and although I never thought routing ten gig ethernet was a good idea (you don't want your edit assistant assigning the backbone network traffic!) it will be important for both baseband and IP 4k.

Whilst on the subject of Barnfind I have a 1350nm SFP which when in a demo chassis caused an intermittent yet repeatable fault; routing 1.5G video (1920x1080 @4:2:2) through it would cause CRC errors in only the AES packets; the signal was then sent to a BT facility line and the first MPEG-encoder it hit at the tower showed the fault by both video and audio disturbance every few seconds; I assume that is down to how that model of encoder extracted timing information. Swapping the SFP out for a new one (exactly the same model) drove the fault away but putting the existing one back re-introduced the trouble.
I am flummoxed how a format converter can reach into the SDi stream and corrupt the AES CRCs - it doesn't seem possible and so I was eager to get it back to the workshop to test it and get a bit more info. So - I have replicated the configuration as much as is possible - even down to the 1000m fibre drum we keep to hand (it's 250m of four core with the ends spliced-back on each other). 
However - the thing has been on 24-7 since last week with my trusty Tek WFM7120 monitoring it waiting for any errors to show and there has been nothing! Do I trust this SFP now? I suppose if I keep it in the demo kit it will be a good test.

Monday, September 21, 2015

"Physics is the only real science; The rest are just stamp collecting..."

You may know this quote by Ernest Rutherford and although biologists and chemists would maybe argue, all scientific people, when they get down to it, know exactly what he meant. We just happen to have given a different name to the physics of living things or the physics of chemical reactions. It's where pseudo-science (Marxism, homeopathy, NLP, Intelligent Design, horoscopes, etc etc etc.) will always show their true colours by not subscribing to the empirical method and falsifiability.

I can recall my first occasion of being aware of physics; aged seven my Dad and I had just watched "The Dam Busters" on TV and decided to build a model of the Möhne Dam out of Mechano. The final touch was two motor-driven gun-turrets powered off a 4.5v bike-lamp battery. Initially the two small motors span too fast to be convincing but my Dad showed me how rather than having two wires going to each motor we could take just one from the +ve terminal of the battery, connect the -ve terminal to the metalwork and earth the 2nd terminal of the two motors. Now, aside from providing an illustration of how car electrics work the two turrets also span a bit slower and my Dad explained that it was down to the resistance through the joins in the strips of Mechano. I understood voltage and (maybe) current at the time, but resistance to current was new and I realised that there were things going on that I didn't yet understand but I needed to!

Spin forward ten years and I was just starting a degree in physics, the very first lecture I attended had a great illustration of how poor our instinct is for all this stuff. The lecturer put up a graph with size on the X-axis (ranging from the diameter of a hydrogen nucleus to the width of the observable universe - suffice to say it was a logarithmic scale!) and velocity on the Y-axis (stationary all the way up to C - 3 x 108 ms-1, the speed of light - the fastest anything can go; God's speed-limit if you will). He then drew on a box which represented most people's experience;
  • Smallest thing; for most people it's the width of a human hair or similar. I look down a microscope often to inspect fibre optic cable, so maybe for me it's a couple of orders of magnitude smaller; 10-5m
  • Largest thing; maybe all that you can see from a high mountain - 1010m2
  • Slowest thing; me in bed! 
  • Fastest thing; traveling in a modern jet liner - 300 ms-1
When you look at that box on the whole graph you realise how poor our experience is against the whole of creation and how you should perhaps trust the numbers rather than your own intuition.
So, physics is hard from a gut-feeling point of view. I changed degrees at the end of my first year to maths & programming but never lost the love of physics. Here are a few things that have helped me along the way.
So, just to stay with the popular science, I heard a great podcast in the "How to be amazing" series with Brian Greene; if you need a bit of a jump-start with your physics then he's your man!

Tuesday, August 25, 2015

Electrical Safety and Best Practise 101 - course notes

I'm off delivering my day-long mains course tomorrow at the University of Hertfordshire. You can grab my notes.

A lot of this has been covered in past episodes of my video podcast.

17th Edition, 3rd Rev.

Saturday, July 25, 2015

The Engineer's Bench podcast - "KVM-over-IP and Data Encryption"

Hugh and Phil talk about KVM-over-IP systems with particular reference to Teradici and Phil's favourite manufacturer Amulet Hotkey. They also go over the basics of encryption with symmetric and public-key crypto.

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

Wednesday, July 22, 2015

Typical edit suite monitor calibration; some traps for young players

I spent the morning in a very typical Soho edit room with a JVC DT-V24-series LED-backlit LCD as the "front of house" monitor and an LG LED-backlit LCD as the client display.
It's quite easy to get the JVC looking right - BBC style 6504k for Rec.709; I've waffled on about this a lot in the past, but I had some new encounters (due in some small part to the new version of ChromaSurf; the software I use with the Klein K10A probe).
  • The Klien is a fast photometer, able to make a reading in around a second; this has huge implications for LUT building and it's why when using LightSpaceCMS you can profile a 17-point LUT in less than two hours. Older probes that can take ten seconds when coupled with something like SpectraCAL (which does not have a proper colour-engine, it essentially halves the difference every time is sees a bad colour match) might have your waiting more than a day for the same LUT profile. Being such a fast probe means that in the current release of their software you can do a 32-sample read of very low (i.e. noisey) blacks and get a reasonable figure. 
  • Just because you can read down at sub 1Cd/m2 doesn't mean you should! With LCDs when you get to sub 5% black you actually see more of the colour of the backlight leaking around those little thin-film transistor pixels. This is why I tend to calibrate black level ("Bias" in Sony-speak) around 15% to make sure I'm getting a real read from the pixels.
  • Even if a domestic display claims to have a Rec.709 mode don't believe the hype; this is the abuse I had to land on the display to get this one to match the JVC and for the Klein to be happy.