3D-HDTV Another Go Round the Mulberry Bush? David Wood, Chair DVB CM-3DTV, Chair ITU SG6 WP 6C, Deputy Director, EBU Technical

A leading toy maker used to attach a label to his Superman costume: “Warning: Cape does not enable user to fly”. Do we need a similar note for 3D-HDTV?

We all know the concept of 3D is not new, and that we have seen cycles of 3D excitement at 30 year intervals for the last 90 years. It’s obvious that the idea of being able to see volume in television pictures is fantastic. But can 3D HDTV, as technically possible today, deliver sustainable success for programme providers and set makers? The answer is probably yes - if only we can ‘manage expectations’ to realistic levels.

There are two main areas for this ‘management’. The first is in the viewing environment and the second is in the programme making environment. As well as this, as explained later in the article, the DVB Project is progressing well with the first 3DTV broadcast standards.

Viewing 3DTV

3DTV as seen today is not entirely the 3D we see in natural vision. It is what the ITU terms as a ’First Generation’ 3D TV system, which means it is served by displaying two images (L, R) in succession on the same screen, one for each eye. When we see these images emitted from the TV screen, the light wave has the ‘phase’ of the TV screen, not that of the original objects in their natural state.

Because of this, our eyes have to do something they don’t do in natural vision – point where the object is in ‘virtual space’, yet focus on the screen. This can cause eye discomfort, and a small proportion of people cannot ‘fuse’ the left and right images under these conditions.

Watching with glasses, you need to keep your head relatively static and vertical to get the right volume effect. Don’t lie down on settee with you head on its side or the volume will disappear!

This adds up to the need to sensitize viewers - suggesting that they do not view 3D HDTV for very long periods without taking off the glasses for a while, and not to think they are sub-human if they cannot fuse the images. And, that there is to be no slouching when watching 3D HDTV.

The truth is that we also need more research on the psycho-physical aspects of 3D TV viewing, and particularly need to examine 3DTV and children.

3D TV Programme making

There are also limitations on 3D HDTV programme making, however much we love it. The volume effect that we see in natural vision is achieved by our eyes, which do not have zoom lenses, looking at objects from ‘eye height’, which are relatively close to us – up to about 10 metres. So, it seems obvious that the recipe for the most natural (and best) 3D HDTV

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would be to shoot relatively close objects from eye height, with lenses of about the same focal length as the eye’s. This needs to be a the staple diet of 3D HDTV. Just dig out the old cardboard ‘stereo-views’ from your granny’s attic, and you see that back then they really understood what 3D shot composition works best.

There are tricks you can use to shoot objects further away - move the stereo shooting camera lenses further apart. This gives you a ‘giant’s eye view’, and you can combine this with the use of longer lenses. But, you need to be aware that any arrangements apart from the standard camera lens (6.5cm) separation, brings into play other elements of unnaturalness. The use of these techniques, and poking the image a long way forward of the screen, need to be used carefully and sparingly.

Overall, then, 3D HDTV is not going to be suitable for all kinds of content, and will need a learning process in production grammar, naturalness, and eye-discomfort.

What kinds of programme content will best suit 3DTV? Probably scenes where there are individuals or small groups of people, and where the camera can get quite close. My money would be on an interview, a boxing match, or a soap opera. 3DTV can be used for ‘wide canvas events’ like football, but the 3D is not going to be as ‘true to life’ and effective as ‘small canvas events’.

This means that 3D HDTV is not going to ‘replace’ HDTV – where the limitations on production grammar are fewer - but it will exist alongside HDTV as something to be enjoyed from time to time when it suits the content.

Broadcast standards for 3DTV

One of the elements that will affect the rate of uptake of 3D HDTV is technical standards. Can we ever doubt that standards wars slow down product acceptance, reduce content choice, and in the end have to be paid for by someone? The DVB Project began its serious work on 3DTV broadcast standards at the beginning of 2010. In autumn 2010, this is proceeding well.

As usual for the DVB Project, two ‘activities’ were started. The first is to establish the elements the 3DTV broadcast format(s) need(s) to have to be a commercial success. The second is to develop the technical specification to deliver them.

Where is the ‘Business Case’ for 3D TV? Two environments emerged – one where viewers keep their existing set top box (but buy a new display), and the other where they buy both a new box and a new display (or a new receiver with everything integrated). The first environment is called ‘Frame Compatible’. To-date it has been the focus of development of requirements and the specification, and we hope the specification will be largely

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