Article in Broadcast Film & Video magazine, no.2

Wow - I'm appearing in this magazine every month at the moment! This article is all about "value-added systems integration"

Article in Broadcast Film & Video magazine

This is an article in Broadcast Film & Video which was a re-write of a presentation I did over the summer. You can see it as a PDF here.

Technologies that made the difference in Television

Will Strauss (writing for Broadcast Magazine) asked me for a couple of ideas for an article he was putting together; you can read it here. My Engineer's Bench collaborator Hugh Waters got in with SMPTE timecode.

The original ideas I sent to him were;

1. The Mostek MK4096 Dynamic RAM chip (and subsequent MK4196 16k DRAM) was the enabling technology that allowed construction of all early digital video devices in the seventies; TBCs, Framestore Synchronisers and Digital Video Effects (ADO, Quantel 5000, Squeeze-Zoom etc) - being dynamic memory these chips required constant refreshing but the nature of video is that the store is constantly being read to make the next line or frame of video. The chips were fast enough that once multiplexed in banks of (typically eight) video pixels at around 75nS clock could be stored. Without DRAM there would have been no picture-in-picture, no timebase correction, no standards conversion, no digital video effects and no digiscan telecines.
2. The Discrete Cosine Transform - as a mathematical technique for transforming pixels into frequency distributions the DCT doesn't actually provide any reduction in data for digital TV signals but it does then allow all manner of compression to take place. MPEG2 in the nineties allowed DVD, Transmission servers and DVB-T and DVB-S powering the first wave of standard-definition digital television. In the noughties MPEG4 and later variants (H.264, AVC etc) allowed HD pictures to be compressed to data rates unthought-of previously. Most contemporary video compression starts with the DCT.
3. Pixel and even frame-free video(!) - this will be the enabling technology of the next decade that will usher in ultra-high-definition TV. Prof Phil Willis of Bath University is pioneering work that will make video a descriptive object technology rather than pixels, lines and frames. Once divorced from set resolutions and framerates it will be up to the display device to render the vectors, contours and shaders at whatever resolution and framerate the device supports.

Video and high-speed networks - article in Broadcast Engineering Magazine

What an up-market magazine Broadcast Engineering is! Well, when they publish my stuff.
You can snag a PDF of the print version from my DropBox; BroadcastEngineering_Article_Nov2010.pdf

Root6 training

This stuff seems to be getting some traction! I always wanted to diversify a bit and although we've not run many courses yet I'm looking forward to more. The last one I did at Bertorelli's last month was well attended and I got a lot of good feedback.

Telcos and dark fibre

My institute's magazine is superb - unlike most industry/free rags it is readable and reminds me of how good Scientific American was in the eighties. One of the best articles last week was on the amount of dark fibre there is in the world. The link (above) is to the article;

The telecommunications industry built too much fibre-optic network capacity during the 1990s. Companies such as KPNQwest, FLAG, Global Crossing and Tyco borrowed too much money and laid too much fibre, and suffered the consequences. Is that over-capacity still present? It’s not clear.

This diagram is missed out of the HTML version of the article.

10-gig Ethernet article from TVB Europe magazine

After the sessions at the Broadcast Live show (last month) and the Root6 Tech Breakfast (this week) my rambings about ten gig ethernet and OM3 fibre appear in TVB Europe magazine - see the article here.
Cabling for high-speed networks seems to be my shtick at the moment.

You may need to do Save As - for some reason my Linux box ain't serving up MIME types properly!

Fibre cabling for editing workstations

Another article for the Root6 catalogue

As our need for higher speed data transfer increases and the advantages of shared storage become apparent to post-producers – high definition television places a requirement on disk space several times that of standard definition and big productions require editors to collaborate on shows. With all this in mind it is no surprise that we’re leaving SCSI behind and our Avids are increasingly using cheaper commodity-based FireWire storage for low-end DV-based work and fibre-channel for larger SAN (“Storage Area Network”)-based collaborative workflows. At Root6 we’ve seen an increase in SAN sales over the last year with Facilis’s Terrablock product line hitting the price/performance spot for many users.
With this as the background, we now do a significant amount of fibre installations as people look to future proof their facilities. The differences between traditional data fibre and the “young turks” who operate SANs, are significant and the lack of appreciation of those differences has caused many an installation gaff for integrators who haven’t taken the time to appreciate those details.
The biggest difference between data networks and “virtualised SCSI” is in the glass(!) – fibre channel works in a “multi-mode” – many frequencies of light are launched down the same glass fibre cable which will maintain data rates below 10 gbits per second over several hundred metres. Single mode fibre, which has longer been used for more traditional data applications – typically TCP/IP – uses a single colour laser and so the glass can be optimised for that “mode”. Data rates of fifty gigabits per second are achievable over tens of kilometres without amplification. These details are given but after that there are a few other considerations that make the difference between a working installation and a truly flexible/scalable one.
When you buy some fibre-channel storage the manufacturer will ship you patch cords that are commonly refered to as “tight-buffered” cable.

The glass fibres are lined in a nylon jacket which is coated in a plastic sheath. These cables are cheap to manufacture and are flexible enough for dressing within equipment bays. The problem with tight-buffered cable comes when you try and run long lengths of it through voids and dry-risers (between the machine room and the edit suite, for example) – it isn’t really man enough for the job and will often fail. Traditional cable-working techniques tend to compromise it, which is expensive if you have to hire wiring staff or worse still if you lose the edit because the cable has just given up the ghost during that important job. The attraction to most in-house engineering departments is that you can buy the cables ready-made and so you don’t have to concern yourself with manufacturing leads that you have little familiarity with.

By far the better way of providing a fibre infrastructure is to run in a “loose buffered” cable. The construction of this differs in that the fibres float in a mineral oil that is contained within a plastic hose. This is wound in a Kevlar mesh (the same material they make bullet-proof vests out of!) which is all covered in a plastic sheath. The cable scores over tight-buffered cable, in that the fibres can slide within the oil as the cable is pulled around bends and the Kevlar means you can step on the cable and abuse it a lot more than patch cord cable. The bulk of the cost of the cable is in the protective construction and not in the glass fibres themselves and so it becomes very economical to run in a four-core where you might only need two (a transmit-receive pair) or a twenty-four core where you only need eight (for example) – this price scalability means you can future proof yourself (you always end up building more edit suites!) and guard against possible damage (despite the glowing account above it does occasionally get damaged). Neither of these advantages can be ascribed to tight-buffered cable. Although the initial installation cost is marginally higher the total cost of ownership and reliability/flexibility is an order of magnitude better.
Root6 has invested in both training and the necessary equipment to offer a full fibre installation service and will be happy to advise when you are thinking of investing in a SAN. As an aside, in the eighteen months since we opened the fibre division we have not had to return to a client’s premises to repair a broken fibre – we have had to help out several other clients who’ve found that half of the pre-made tight-buffered cables they’ve had run in have failed very quickly.

"The perils of colour-space conversion" - an article for the Root6 Dr. Watson newsletter

At work we produce a newsletter which I sometimes do a technical piece for - so forgive the slightly client facing tone of this piece!

An important aspect of the production/post-production chain is maintaining correct colourimetry. If the director of photography or the lighting-cameraman want that certain shade of red to be correctly delivered to the viewer then attention needs to be paid to the correct representation from the camera (be it standard or high definition or even film) through all transfer operations (potentially going between resolutions, YUV/RGB colour spaces and bit depths) to the final display surface (be it a CRT, LCD or even cinema screen). In truth colour-space management for film is a complex issue best handled by specialists like Filmlight (who are represented in the UK by Root6) and is perhaps beyond the scope of some technical notes in a newsletter! That said there are many points worth making if you are acquiring or delivering for high definition television and worried about going between colour spaces.

The CIE Chromaticity diagram (first published in 1931!) shows the gamut of human vision – essentially any display surface is a subset of this diagram and will be a triangle with red, green and blue apexes and white (actually monochrome – as the luminance of the image is reduced it tends through grey to black) in the centre. In the case of “illuminant D” (AKA “D6500” or “EBU phosphors”) – the standard definition colour standard used since the sixties in Europe we enjoy a slightly wider red range than our colonial cousins but every gamut (television, film or print) is a poor compromise on what your eyes can handle. This is where the problem begins – you have a very critical instrument at your disposal to see these differences.

Part of the problem is that all of our machines acquire images in the RGB space (TV cameras, Telecines, graphics workstations etc.) but for the most part we post-produce in a YUV space (with the exception of Sony’s new HDCam SR format, an RGB high-definition VTR) which represents an immediate lowering of the colour space. This has been the case for a long time and is well understood. Manufacturers have agreed a common “matrix” for transcoding. To make the luminance portion of the component signal the following is used:

y = 0.299 * r + 0.587 * g + 0.114 * b

Well, this is the case for standard definition (AKA “601”), but for high-def (AKA “709”):

y = 0.213 * r + 0.715 * g + 0.072 * b

Which, even if you’re not so into the maths, will give different values for the luminance (the overall level and hence look of the picture). This makes it doubly important that you get your cameraman to record some colour bars at the head of each rushes tape and that your editor checks alignment on his scope before he starts adding captions etc. The best of breed digital picture instruments are from Tektronics who Root6 are pleased to represent.

If you find you have a colour space issue (particularly going between standard and high definition formats) then the Belle Nuit Montage test chart is a good starting point. It can highlight all the common transcoding errors – be it the limited 8-bit range of old D1 videotape to some of the sub-sampling issues associated with HDCam. You can download the file at various resolutions from their website and by injecting it at the start of your workflow any inadequacies are quickly revealed and can be corrected.

Article in this week's Broadcast

See the full thing here

computer displays -v1.pdf
2nd article for the tech section of the Root6 catalogue.

I had to write the following for someone!

Why I prefer the look of interlaced video


I’ve been engineering in television since the eighties when I started at the Beeb working in television news. All the training efforts of the good folks at Wood Norton (the BBC’s own college!) were to turn out staff who could maintain the fidelity of pictures and audio from acquisition to transmission. As the nineties wore on and TV stopped being staffed by people who earned their chops and became the domain of “meeja skool” graduates the practice of film-looking increased – trying to make pictures acquired on tape look like they really came off film. It rarely works – making video look jerky and messing about with its colour grading is more an insult to people who work in proper film than those of us who think video looks better than film on television. One of the areas where video out-performs 35mm is in motion rendition, and so why spoil that?
The reason production types indulge in this kind of behavior is to do with the perception that film-produced TV looks more expensive than the kind that comes out of a studio. For my money I find clean, well lit video to be more engaging than film because it looks a like the world does. When I watch “Casualty” I can believe it a bit than, say “ER” because with the latter I can never quite loose the feeling that it has been shot on a sound stage and has gone through a much more elaborate post-process. Video seems more true, more honest.
Now me venting my engineering spleen about all this came about because of the “Give it the Bullet” article in a recent edition of Creation – “Make your cheap-skate DV production look like Super-16” or some such! My answer to this is the two episodes of Dad’s Army that Steve Roberts at the Beeb restored a couple of years ago. They discovered these missing episodes in a shed on reversal 16mm from a tele-recording (ask your Dad). Being aware that these gems would have gone out as video Steve set about finding a way of making them look like interlaced video again (it’s the honesty thing!) and he discovered VidFire – an AVX plug-in that turns film into video – it fills in the temporal blanks. It really does work – it produces smooth motion from jerky old film. Now that is a fashion I could support – video-looking film. If someone could produce a real-time unit and build it into my TV set then I’d be happy!

Cabling for AES audio
An article by Simon Croft from Post Update magazine (November 1998) based on an interview with me (while I was working at Oasis TV) explaining the pros and cons of sending AES digital audio over balanced and unbalanced cable. Kind of innovative at the time but par for the course now!