« Topics
harshy6,369 posts since 24 Mar 2001
I still think this 3D revolution is heavily mistimed. A lot of people are still getting to grips with the HD revolution, buying new sets and HD receivers and stuff - I dunno about you, but I can't be arsed looking into 3D TV for another 20 or 30 years.

But that is Sky's business model,they always need to be introducing a new generation of equipment and they don't wait for the previous 'next big thing' to be universal first

Almost 12 years ago they started moving everyone from analogue to digital, then before everyone had Sky Digital, Sky+ came along and that was the revolution being pushed. Then HD came along and Sky subscribers were being encouraged to upgrade to that, even though a lot of them hadn't even got Sky+.

Sky always need something else on the horizon to move people over to, so now it's 3D, the difference this time is that it's new TV's rather than new STB's that are being promoted.

I do wonder what will be next though, they will need something else in a couple of years

The next thing will not only be 3D, but smellyvision! Laughing
Steve in Pudsey10,557 posts since 4 Jan 2003
Yorkshire Look North (Yorkshire)
Thanks, as ever, for the technical insights, noggin - I appreciate the additional costs in having a single mix, but in my opinion having seen yesterday's coverage it needs a lot more cameras to be worth watching, particularly as the one 3D screen in a pub is much smaller than the projector type screen or multiple plasmas/LCD screens it replaces. Sticking on a wide shot from the halfway line for a long time just isn't engaging enough, the action is too small to see.

However, as I speculated in the Sports thread, I think they could have been having Vision Mixer issues for the first half an hour, as there a very limited selection of cameras used, and no score/clock bar DSK, so I suspect they may have had to use emergency cut for the beginning of the match.

I have a question. I have only had the opportunity to try the coloured 3D glasses, and I couldn't combine the images - therefore leaving me watching a film in blue for two hours.

Would the same effect be noticeable on polarised lenses, leaving me with a stripy image?

As far as I could tell, the lenses for the current Sky system are very much like polaroid sunglasses, just that each lens is polarised perpendicularly to the other. So everything is just a little darker than usual.
Write that down in your copybook now.
Brekkie33,301 posts since 4 Jan 2003 Recently warned
HTV Wales Wales Today
I really don't think it will take off until a system is in place where you don't need cardboard glasses to watch it.

I've also visions of tonnes of complaints when it gets beyond sports and people get scarred **** when a lion jumps out of a nature documentary towards them! Laughing
It's great that everybody gets sarcasm.
noggin14,704 posts since 26 Jun 2001

As far as I could tell, the lenses for the current Sky system are very much like polaroid sunglasses, just that each lens is polarised perpendicularly to the other. So everything is just a little darker than usual.

Sky don't have a chosen display system - beware of assuming "Sky system" is polarised glasses based because the pub screens are. That isn't a conclusion to jump to.

Sky are using a TRANSMISSION system called "side by side" - mainly because it is the only system that delivers 50Hz motion AND is compatible with 4:2:0 subsampled H264 transmission (i.e existing Sky HD boxes). If you tune to channel 217 on a Sky HD box you see the left and right eye feeds 50% subsampled horizontally (i.e. 2x 960x1080/50i streams next to each other) 4:2:0 chroma subsampling causes problems for transmission using chequerboard and alternate line standards I believe, though top/bottom could be used?

However this is just the TRANSMISSION system.

How a TV DISPLAYS this stream is entirely a function of the TV - and nothing to do with the transmission system Sky are using.

All a TV has to do is recognise (or be told) that it is receiving a side by side feed - and then display it in a way that works with its chosen 3D technology.

For polarised pub screens, they do this by stretching the 960x1080 left and right eye feeds to 1920x1080, but then sending only 540 lines of the left and right eye feeds to alternative lines on the 1080 line display (i.e. discarding half the lines of each eye - though they probably filter to avoid aliasing), with each alternate line polarised alternately so that the left eye sees one set of lines, the right eye the other set of lines. This delivers 960x540 resolution (though with fast motion in 50i this vertical resolution reduction isn't so huge, however with 25p movies it is much more significant), but both eyes see a picture at the same time. The polarisation filtering also dims the image (as some light is being blocked)

For active shutter domestic displays, they do this by stretching the 2 x 960x1080/50i stream back to 2 x 1920x1080/50i and then de-interlacing to 2 x 1920x1080/50p, and then outputting these as a single 1920x1080/100p or 200p stream. An infra red signal is sent from the TV to active shuttered glasses that you wear, to synchronise them to the 100/200Hz frame sequence, allowing the left and right eyes to be blanked for alternate frames. Thus the eye gets a full 960x1080 resolution image - but you don't get both eyes seeing a picture at the same time.

Polarised screens are more expensive to manufacture - as there is an extra process in production compared to 2D displays, and they have reduced resolution in 3D. (Particularly an issue for Blu-ray which uses full 2 x 1920x1080/24p resolution) However the passive glasses are cheap and can be effectively disposable.

Shuttered systems need no more manufactuing processes to be added to the screen - 100/200/400Hz screens are being manufactured for 2D. The only additional requirement for the display is some processing (probably almost zero cost after development has paid off) and the IR emitter (which could be optional) It also offers full 1920x1080 resolution to each eye. However the glasses are active (need batteries or charging) and much more expensive than passive polarised glases.

So polarised with passive glasses are good for mass viewing - like pubs (and cinemas) Active shuttered are possibly better for the home, as adding compatibility with 3D can add very little to the cost of set manufacture - instead the glasses add the cost. However the shuttered system can be an upgrade you could do at a later date (with 3D Ready being a possiblity)

Sky is compatible with both systems - they are display-agnostic...
noggin14,704 posts since 26 Jun 2001
I really don't think it will take off until a system is in place where you don't need cardboard glasses to watch it.

For family viewing, glasses are going to be with us for a while. However active shuttered looks like it is the chosen format for domestic systems (as it doesn't add to the display costs massively) - so rather than cardboard glasses, you will be wearing Ł75 flickering shuttered glasses that need recharging or battery replacements.

There are already some nicely designed polarised specs for people who don't like the cheap cinema-supplied ones - though as someone who wears glasses at the cinema, I prefer the "safety specs" ones that go over glasses. (Though internal reflections when wearing two pairs of specs can be annoying)

There are glasses-free systems that use lenticular screens. These can work well for single viewers (Nintendo's new 3D DS system uses one, as does the Fuji W1 3D stills camera) - but you have a limited number of viewing angles, and can't move too much. I saw the large screen glasses-free system at NHK last year. It was effective but uncomfortable - and if you moved your head too much you got double imaging.