[Noginthenog]

Probably a very quick answer to this question....

I finally persuaded my better half to allow me to get SKY HD.... after installation I've noticed in the setup that it say Max Resolution 1080i. I mistakenly assumed it would be 1080p.

So question is - does sky only transmit in 1080i or is it my box that is throttling back?

[KevIW]

Yes Sky transmit 1080i only.

[GasDad]

Originally Posted by Noginthenog

Probably a very quick answer to this question....

I finally persuaded my better half to allow me to get SKY HD.... after installation I've noticed in the setup that it say Max Resolution 1080i. I mistakenly assumed it would be 1080p.

So question is - does sky only transmit in 1080i or is it my box that is throttling back?

1080i is the same resolution as 1080p.

For movies sky transmit 1920 x 1080p/25. (Blu Ray is 1920x1080p / 24 - though at much higher bandwidth)

For nearly everything else it's 1920 x 1080i/50. - this means each frame (1/50th of a second) has every other line - but due to movement between frames it reduces the effective resolution slightly. But it is better for sport etc than 1080p/25 used for movies.

BBC HD and possibly ITVHD use a slightly lower horizontal resolution.

[mikelj]

Originally Posted by GasDad

1080i is the same resolution as 1080p.

Not quite. If whatever de-interlacer is being used cannot determine the difference between film (i.e. progressive) and video (i.e. interlaced), then you may effectively be loosing half the resolution. For example, 1080p25Hz transmitted at 1080i50Hz, de-interlaced as video may result in either all the odd/even lines being discarded in favour of interpolated data, in order to display a 1080p image.

[choddo2006]

Originally Posted by GasDad

1080i is the same resolution as 1080p.

For movies sky transmit 1920 x 1080p/25. (Blu Ray is 1920x1080p / 24 - though at much higher bandwidth)

For nearly everything else it's 1920 x 1080i/50. - this means each frame (1/50th of a second) has every other line - but due to movement between frames it reduces the effective resolution slightly. But it is better for sport etc than 1080p/25 used for movies.

BBC HD and possibly ITVHD use a slightly lower horizontal resolution.

That's a teeny bit misleading.

1080i/50 is the same effective resolution as 1080p/25 (as long as your deinterlacer processes film sources properly)

If you don't specify refresh rate, 1080i is not the same resolution as 1080p. If you could get sport at 1080p/50 it would be an improvement on 1080i/50.

[grahamlthompson]

Originally Posted by choddo2006

That's a teeny bit misleading.

1080i/50 is the same effective resolution as 1080p/25 (as long as your deinterlacer processes film sources properly)

If you don't specify refresh rate, 1080i is not the same resolution as 1080p. If you could get sport at 1080p/50 it would be an improvement on 1080i/50.

I don't follow that argument at all SKY HD is 1920 x 1080 delivered in two fields of 1/50 sec each from its DVB-S2 transponders. That's an identical resolution to a 1080p25 1920 x 1080 delivered in a single field of 1/25 sec. The interlaced signal may have motion artefacts but it's got the same number of pixels in each full frame. BBC HD and ITV HD on DVB-S transponders use 1440 x 1080i. Nobody transmits 1080p50 which needs way too much bandwidth. In any case whatever the signal is (576i or 1080i), the resolution of the displayed picture is identical on a HD matrix display which has to display it's native pixel count.

[choddo2006]

Originally Posted by grahamlthompson

I don't follow that argument at all

You don't follow that 1080p/50 has more resolution than 1080i/50?

SKY HD is 1920 x 1080 delivered in two fields of 1/50 sec each. That's an identical resolution to a 1080p25 1920 x 1080 delivered in a single field of 1/25 sec. The interlaced signal may have motion artefacts but it's got the same number of pixels in each full frame. BBC HD and ITV HD on DVB-S transponders use 1440 x 1080i. Nobody transmits 1080p50 which needs way too much bandwidth.

I know but the point remains that "1080i" and "1080p" are not the same.

I guess it's fair to say that 1080i and 1080p as used most often (1080i/50 and 1080p/24) are pretty much the same but consoles (for example) are just one source of 1080p/60 content and it's confusing to not make the distinction clear and all the technical gibber about transponders doesn't help people understand.

In any case whatever the signal is (576i or 1080i), the resolution of the displayed picture is identical on a HD matrix display which has to display it's native pixel count.

Of course. The resolution is the same - the picture isn't. and the same is true of various TVs' handling of 1080i.

[grahamlthompson]

Originally Posted by choddo2006

You don't follow that 1080p/50 has more resolution than 1080i/50?


.

It does not have more resolution, that does not mean that 1080p/50 won't have a better picture but it's not down to resolution. In any case when have you seen a 1080p/50 signal, where did it come from ?. Bitrate has a much more effect on picture quality than resolution , why do you think bluray 1080p24 looks so good it's still 1920 by 1080

[choddo2006]

Originally Posted by grahamlthompson

It does not have more resolution, that does not mean that 1080p/50 won't have a better picture but it's not down to resolution. In any case when have you seen a 1080p/50 signal, where did it come from ?.

1080p/50? Loads of times. PC. xbox. PS3.

Bitrate has a much more effect on picture quality than resolution

Of course. Not relevant to this discussion though (in which I'm trying to point out the OP was being slightly led astray)

why do you think bluray 1080p24 looks so good it's still 1920 by 1080

Who said 1920x1080 didn't look good?

But the fact is a lot of TVs will introduce artefacts in 1080i so that it doesn't look as good as the exact same bitrate picture at 1080p at half the refresh. Some won't, but a lot will.

[mannyo]

Sky as already mentioned is 1080i, I dont think I am aware of a single broadcaster worldwide currently using true 1080P because of the huge bandwidth requirements of the broadcast.

[choddo2006]

Originally Posted by mannyo

Sky as already mentioned is 1080i, I dont think I am aware of a single broadcaster worldwide currently using true 1080P because of the huge bandwidth requirements of the broadcast.

... although industry tests have shown 1080p could be broadcast in less bandwidth than you think - something like an increase of 40% I think it was. We're clearly still too far down the path with 1080i acquisition and distribution, plus all the boxes out there to expect anything to change on that front for years though.

[GasDad]

Originally Posted by choddo2006

That's a teeny bit misleading.

1080i/50 is the same effective resolution as 1080p/25 (as long as your deinterlacer processes film sources properly)

If you don't specify refresh rate, 1080i is not the same resolution as 1080p. If you could get sport at 1080p/50 it would be an improvement on 1080i/50.

Err that's why I said the effective resolution is decreased.

[choddo2006]

Originally Posted by GasDad

Err that's why I said the effective resolution is decreased.

Sure, and you're right. It was more the opening assertion that they are the same I was challenging. It was a very definitive statement.