Strictly in 3D – bandwidth

I posted a couple of weeks ago about the impending broadcast of Strictly Come Dancing in 3D, and I thought a few readers might be interested to know how it all worked out.

The 3D broadcast on BBC HD was preceded by a screen explaining to viewers how to set their TV to the appropriate ‘side by side’ mode, which should have been fairly simple for most – on the Samsung set I was using, it’s the first option that appeared when I pressed the 3D button on the remote control. And on the whole – at least until my guest sat on the glasses and broke them – it worked pretty well.

But what about bandwidth? Well, I’ve checked the recording sizes and durations for the 2D and 3D broadcasts on Freeview HD, as reported by the Digital Stream box that I’m currently using for HD viewing.

The 3D recording of the results show lasted 1h 4m 19s, and took up 4.5GB of disk space

The 2D recording from BBC One HD lasted 1h 4m 28s, and took up 4.8GB.

The difference in timing is probably a combination of the response time of the recorder, and slight differences between the flags being updated on the two channels; at any rate, nine seconds over an hour is negligible and we can, broadly speaking, consider each recording to be about the same length.

So, that leaves us with 4.5GB for 3D and 4.8GB for 2D, and I think that’s more or less in line with what I’d have expected, though there would need to be a lot more 3D around to be entirely sure.

The bandwidth on Freeview HD is shared between the four channels, and the BBC ones at least are ‘statistically multiplexed’, which means that if one channel is showing fast changing information, compared to something more static on the other, then the channel that needs more bandwidth can get it – think, for example, Match of the Day vs Great Expectations. Match of the Day will very likely get more bandwidth.

But, of course, for Strictly, it was essentially the same programme on two channels, and so the end result was always going to be pretty similar, and for the short to medium term at least, I think it’s pretty much inconceivable that any 3D broadcast won’t also be accompanied by a 2D simulcast, certainly on the BBC.

Why is the 3D broadcast slightly smaller, though? My suspicion here is simply that it will compress a bit better; 3D using the ‘side by side’ format has two almost identical pictures making up each frame – and in doing so, incidentally, halves the horizontal resolution of the 3D picture, compared to the 2D one – and that means more repetition.

Repetition is what compressors look out for, so that they can save space, so my gut feeling – and if you know more about the intricate innards of broadcast compression feel free to comment – is that the side by side format will tend to compress slightly better than a comparable full-frame HD picture.

As to what it looked like? Well, for the bits that I could see, the lovely Harry Judd looked even lovelier in 3D, but like quite a few people, I do find watching 3D a bit wearying, and the standard HD picture was, overall, crisper and a lot easier on the eye.

Strictly Come Dancing in 3D

During last Saturday’s show, the presenters of Strictly Come Dancing made much of the fact that the final will be broadcast in 3D. A look at the comments on the website for the show reveals that quite a lot of viewers are rather confused about whether or not they’ll be able to watch in high definition, so here’s my attempt at clarifying what’s happening (based on my own post on that blog).

I don’t have a 3D set. Will I still be able to watch Strictly in High Definition?

Yes. The normal BBC One HD broadcast will still be happening, so you won’t miss out. The 3D broadcast is on a completely different channel.

I don’t have HD. Can I still watch in 3D?

Only if you go to one of the cinemas that’s showing 3D, or if you buy a 3D receiver (like a Freeeview or Sky HD box) and install it before the weekend, and have a 3D TV. Because 3D needs two pictures – one for each eye – it’s not possible to transmit 3D without using an HD channel, and still maintain good picture quality.

I don’t understand! How can it be in 2D and 3D at the same time?

I think a lot of confusion here comes down to the BBC referring to “The BBC HD Channel” when they’re talking about 3D. There are actually two high definition channels from the BBC; one is BBC One HD, which shows whatever is on BBC One, but in high definition, and the other is just called BBC HD, or “the BBC HD Channel”, and carries a selection of programmes from other channels including, next weekend, the 3D version of Strictly Come Dancing.

So what’s on, where?

Here’s the quick summary:

BBC One, standard definition: The ordinary version of Strictly Come Dancing; find this on Freeview 1, Sky 101, Virgin 101, Freesat 101, or on analogue if you’ve not yet switched over.

BBC One HD: The high definition version of Strictly Come Dancing, in old fashioned 2D. Just like every week. Find this on Freeview 50, Freesat or Virgin 108, Sky 143.

BBC HD: The 3D, high definition version of Strictly. Find this on Freeview 54, Virgin 187, Freesat 109, Sky 169.

What do I need to watch in 3D?

You’ll need a 3D television and access to the BBC HD channel; try the channel numbers I’ve listed above, and see if you get BBC HD. If you do, and your TV is 3D, then put on your glasses, tune in on Saturday night, and you’re all set – your TV should automatically recognise the 3D transmission. If it doesn’t, press the 3D button on the remote, and if you have to pick a ’3D format’, choose ‘Side by side.’

Many 3D televisions will have a built in receiver for Freeview HD; if that’s not available in your area, you’ll need either Sky, Virgin or Freesat, and an HD receiver for one of those services.

Will the 3D broadcast be exactly the same as the normal one?

It’s likely to be slightly different, with some different camera angles – different cameras are used for 3D, and some sorts of shots will work better in one format than another. So, expect there to be some differences betweeen the two.

Will I be able to record the 3D show?

Yes. If you have a digital TV recorder, like Sky+, Freesat+ or Freeview+ HD, then just record the show on the BBC HD channel (see the numbers above), and you’ll be able to watch the 3D broadcast later, just as if you were watching it live.

Why isn’t it in a cinema near me?

Lots of the comments on the BBC site seem to suggest this is poor planning by the BBC, but it’s important to remember a couple of things. First, broadcasting in 3D is still pretty experimental, and secondly, not all cinemas are set up for live 3D, even if they can show feature films in 3D.

Feature films are sent out on hard disks, or downloaded to the cinema in advance, and then shown many times. The Strictly final will be live, and so can only be shown in cinemas that have a suitable link to receive live shows and broadcast them directly to the screen, which not all will be set up to do.

Ultimately, whether or not a cinema is set up for that will depend on the company that owns it, not on the BBC, who can’t pay to install equipment in someone else’s commercial premises. If your local cinema isn’t showing the final, then tell them you’re disappointed. It won’t make a difference this week, but they might realise that there is a market for future events to be shown that way. If you don’t tell them, or just complain about the BBC, your local cinema isn’t going to know they’re missing out on business by not investing in the right equipment.

How does the 3D system work?

For those interested in the technical side, the 3D broadcast will use a system called ‘side by side’. If you tune in to the BBC HD channel and don’t have a 3D set, what you’ll actually see is that the screen has two almost identical pictures, squeezed into the frame. A 3D TV recognises this, and shows one at a time, zoomed to fill the whole screen, and controls the timing with the 3D glasses so that the left eye sees the pictures on the left, and the right eye sees the ones on the right.

One of the consequences of this is that each picture actually has only has as much information as the normal HD picture, because it has to fit into half the screen; you probably won’t notice a massive difference, but that’s why 3D is always used with HD channels – if you tried it on a standard definition one, you’d really notice the difference.

Inside the den of the hot geeks

Last week I had the pleasure of a trip to Manchester, where I’ve not been since the tail end of the 20th century. I was invited by the BBC to look round their R&D North Lab, which is one of the three locations where the Corporation works on a range of research, from digital production to ways of enhancing the experience of the end users.

There’s a team of technologists (or hot geeks, as I prefer to think of them); mostly young men and a few women, ranging from those on placement as part of a course to others who have been with the BBC for many years.

A full report of my trip is over on RegHardware.

Additional information about the “dalek demo” has just been posted on the BBC R&D Blog

A well deserved win for BBC R&D

I’m intending to write a bit more about the BBC Research people in the near future, but I thought I’d just flag up a well deserved award that they received last week, at the annual IBC show in Amsterdam.

IBC is where you’ll find many of the latest developments in broadcasting, and it was two years ago in Amsterdam that I saw some of the first live demonstrations of the DVB-T2 technology that powers Freeview HD.

Amidst all the fuss about the surround sound issues on that service, some people claimed that the BBC don’t invent technology anymore, and just buy in things from elsewhere. That’s not really true. What is true is that the technological landscape of broadcasting has shifted dramatically from the days where the BBC labs could come up with great ideas like RDS or Nicam Stereo, more or less on their own.

In the modern world, international standards are required, and often the role of individual organisations in those doesn’t achieve as high a profile as when they can be said to have invented something themselves. But, nevertheless, the DVB-T2 technology that Freeview HD relies upon wouldn’t be there without the work of the BBC R&D department, who led the team, and provided much of the most important expertise.

They were recognised for that at IBC, with an award for the technology – you can read a little more about it on the BBC blog.

I think it’s important to remember things like this; all too often (and sometimes justly) other aspects of the corporation get criticised, and we forget that there’s an amazing amount of work, some of it so far behind the scenes that it’s easily forgotten, carried out by incredibly clever people in the BBC labs. Their website is worth a look. It’s a reminder of some of the great work that’s carried out on our behalf.

BBC blog on surround sound for FreeviewHD

The BBC has just posted a useful blog addressing some of the issues regarding surround sound, and confirming that it won’t be until April of next year that transcoding is mandatory.

If you don’t have time to digest all the other information on this site to work out what that means, here’s the Executive Summary:

• Most Freeview HD kit you buy right now will not give you surround sound with your existing home cinema system, even where surround sound is broadcast
• To get surround sound, equipment needs to either provide a multi-channel output via HDMI, or transcode it to Dolby Digital/DTS for optical/co-axial connectors
• Some equipment on sale can do that. But most can’t
• It will be a mandatory requirement on equipment launched after April 2011

If there’s too much jargon in this post, read this one for a quick glossary.

Incidentally, also quite interesting to see in that blog confirmation of something I suspected, which is that it’s not really practical to switch audio formats on the fly, without causing various glitches. Many thanks to the BBC for answering the questions that I put to them.

BBC One HD ident revealed

Want to know what those BBC One HD idents will look like? Here are some images, hot from the BBC Press Office.

BBC ONE HD - Eastenders. Thanks to the BBC for this image

BBC ONE HD - Holby City. Thanks to the BBC for this image

BBC ONE HD - The Apprentice. Thanks to the BBC for this image

BBC ONE HD - QI. Thanks to the BBC for this image

BBC One HD to launch this autumn on FreeviewHD and Freesat

The BBC has announced today that a new BBC One HD channel will launch in the autumn, offering a simulcast of BBC One. The existing BBC HD channel will remain, showcasing HD material from the Corporation’s other channels, and will extend to 12 hours a day.

Programmes including The One Show, Weakest Link, QI and The Apprentice are scheduled to move to HD production by the end of the year.

Other long-running shows such as Songs of Praise, Question of Sport and Blue Peter will also be moving to HD. According to the BBC press release:

“The Autumn launch is the first stage in delivering BBC One in HD.  The majority of programmes in the BBC One network evening schedule will be available in HD at launch, and by 2012 it is expected that the vast majority of all BBC One titles across all hours will be in HD.”

The new service will be available on all digital TV platforms that carry HD – that’s Freeview, Freesat, Sky and Virgin Media.

So, now we know what the fourth slot on the Freeview HD mux will be used for.

Update: Regional variations

From the BBC Trust website:

“the Trust also recognised that technical and financial constraints currently prevent additional variations, and asked the BBC Executive to take steps to minimise the effects of this on viewers in the nations and regions.”

So, it looks like this will probably be the main BBC One London feed. I suspect that the considerations are largely financial (eg extra capacity on satellite to deliver regional versions), because I recall at the Freeview HD technical launch, it was mentioned that the HD network had been designed to cope with regional variations.

There’s some more on this at the BBC Internet Blog.

6pm update: Want to see the ident?