Rob's Blog

BBC One HD launched this weekend. Until now, the BBC had a channel called BBC HD that showed what HD contend the BBC made. Now it has a HD channel that shows everything on BBC One. Programmes that weren’t made in HD are upscaled, meaning the SD picture is shown at HD resolution.

Case in point, the footage of Formula One that broadcasters get from Bernie Ecclestone’s organisation is not in HD, for reasons best known to Bernie. Probably he judges that the benefits to him of upgrading his infrastructure are not worth the costs, and he may be right. It’s still annoying, Formula One would look amazing in HD. Maybe next year.

Anyway, the new BBC One HD channel is still a boon to Formula One fans. Because the picture is much better, even though it is not in HD. Why is this?

Well, the picture that the BBC gets from Bernie is a professional quality un-compressed video feed. In the previous scheme of things, the BBC then compresses this video feed into a low bandwidth MPEG-2 stream of about 2 megabits per second or less.

On BBC One HD, however, the BBC takes the same image and turns it into an MPEG-4 stream of about 6 megabits per second. There are several advantages to this. The first is just that the bitrate is higher. MPEG video compression attempts to reduce the information content of the video in a way that your eyes don’t notice.

This works well, but broadcasters judge that putting out many channels makes them more money than putting out only a few channels. And since bandwidth costs money, they cram as many channels as they can into as little bandwidth as possible. So each channel gets fewer bits per second than it might in an ideal world, and you end up with video that doesn’t look as sharp, or that shows blocky artifacts in parts of the picture that are changing a lot, such as a fast moving racing car.

HD needs more bits because it is HD, so when SD video is broadcast on a HD channel, it gets more bits and a lot of the blockyness and fuzzyness visible on the SD channel is not visible on the HD channel.

Here I have taken pictures of my TV of almost the same frame of video. To compare them, right-click and open each one in a new tab. Then switch between the two tabs. The first is from the SD channel:

The second is from the HD channel.

You should see straight away that the HD image is crisper than the SD one. Here’s a look at a small area of the screen. The top image is from the SD channel and the bottom image is from the HD channel.

In particular the center of the wheel in the SD image has less detail. Having more bits available makes it possible to capture more high frequency detail, like the concentric circles made by the aerodynamic features of a Formula One car.

Here’s another example:

The difference here is caused by the higher resolution of the HD channel. Although the source video is only SD, images are split up into 8×8 pixel blocks before some of the information from each block is thrown away. Because there are more pixels on the HD channel, the 8×8 blocks are smaller in relation to the whole picture, so less information is thrown away, leaving more detail. Notice that the number 5 looks smudged in the SD image, and in the HD image you can see the jagged pixels that make up the diagonal line separating the number from the name.

Here’s a final example that highlights another reason that the HD channel looks better:

Not only is the HD image sharper, the letters U and B are more brightly coloured. Another technique of video compression is to send colour information at a lower resolution than brightness information. This is because the human eye sees colour at a lower resolution than it sees brightness. Because the BBC gets video from Bernie that has not had this technique applied to it, and it then converts SD colour to HD colour, the full colour resolution is preserved.

So whenever you can, watch the HD channel even if the programme is in SD, it still makes a big difference.

80-year-old Aunt Fran is awesome. Here she is unboxing a Nintendo DS Lite, which she intends to use for Alzheimer’s prevention.

The guy who made the video also made a video in which he unboxes a brand new Mac from 1997. This is the kind of stuff that keeps you up at 1.20am on a work night…

H/T the Indy. Note that whatever the topic, they can’t ever miss an opportunity: “Boxes weren’t too eco-friendly in those days, however; Al Gore, who now sits on Apple’s board of directors, might have something to say about all that excess cardboard and plastic.”

In Foyles, I bought Digital Apollo, by David A. Mindell. It’s about the design of control systems, and in particular the interactions between astronauts, test pilots, designers and user interfaces. The astronauts at first wanted to be able to do everything manually. In the end, they accepted a lot of computer control, partly because they had some influence in the design of the systems. At least that’s what it seems like from the few bits I’ve read so far.

This is quite profound:

The digital autopilot also confirmed the decision to use a general-purpose computer in the first place and underscored the intimate links between systems engineering and digital computing. Engineers could move particular functions out of hardware devices and into computer programs, saving critical quantities of weight, money and hardware complexity. In one example, Shea nixed an expensive program to add a heat shield for the side of the command module facing the sun. With his knowlege of control systems and the digital autopilot, he simply suggested replacing the insulation with a software routine to keep the spacecraft rotating like a rotissarie, distributing the heat load around the craft. A few lines of computer code replaced a heavy mechanical structure.

The book also contains the astonishing (to me) revelation that computer programs were stored on core rope memory — where wires are threaded through ferrite donuts to represent a 1, or around to represent a 0. These ropes were threaded by hand by little old ladies, earning the ropes the nickname of LOL memory.

I’m on the train from London to Manchester in first class with a table and power socket, and a 3G dongle plugged in to my laptop. It’s pretty amazing that I can do this at all, but let’s just say we don’t have ubiquitous wireless data *yet*.

It works — just. A lot of the time, including any time we go through a tunnel, the data disappears completely. AJAX web apps don’t always behave very well when this happens. Google Mail and Reader at least display useful error messages. Facebook often gets stuck and no amount of refreshing or clicking stop has any effect. Google Gears and similar should improve matters.

Quite often I have a green light, meaning GPRS. This is almost the same as having no connection at all.

When I have a blue light, meaning 3G, everything is pretty good. A blue light might last 3 or 4 minutes at a time if I’m lucky.

Part of the problem is the transitions between states. If you only load half the web page and have a bit of a glitch between cell towers, the whole web page fails and there is no alternative but to start again.

Obviously better data coverage will help. But I think what would be really useful is an alternative to TCP that is designed to cope with internittent connections.

I am impatient to live in a Vernor Vinge novel!

I bought a microwave oven yesterday. Apparently they are useful for babies. Anyway, it has a button labeled “Chaos Defrost”. The user manual only says that this is for defrosting things. You can’t label a button “Chaos Defrost” and not explain the “Chaos” part! It’s too tantalising.

Thank goodness for the Internet. Apparently, random bursts of high-power microwaves will defrost more quickly and evenly than constant low power. I can imagine it has something to do with allowing heat to conduct between bursts. But that wouldn’t need chaos theory to explain it, and the randomness seems important. Unfortunately, the paper is behind a paywall.

I am trying out my new pay as you go O2 Mobile Broadband USB stick. After a few teething troubles (it turns out that a double blink of a green LED means there is no signal, and the steel framed building my flat is in is not good for mobile phone signals) it seems to work very well. On the train it is much better at coping with varying coverage than my T-Mobile G1 phone is. The phone seems to take a very long time to re-establish a connection when it is lost; the 3G modem is quick at this and happily switches between 3G, EDGE and GPRS without too much complaining.

I chose the O2 PAYG one because it has weekly and daily top-up options. I’m likely to be using it very irregularly. £2 for 500MB for a day seems fair enough when I want to check my mail while away, although it really is ridiculously expensive when you think about it, it’s better than paying £15 a month when months might go by without me using it at all.

Now it is time to get off the train. More later, perhaps.

Update: The USB modem only cost £20 and is a Huawei E160. It can do HSDPA but not the fastest 7.2Mbps speeds. But it seems fast enough. There doesn’t seem to be anything special abot these modems: they work on Macs and Linux without special software so there may be alternatives to the O2 Connection Manager software for Windows. And presumably netbooks that have integrated 3G and a SIM card slot can be made to work easily.