Wild China. Really Hd?

[myk]

I've really enjoyed Wild China so far.

I was hoping to see a good demo of HDTV too, but the sharpness was so lacking that it looks like

an upscaled SD version. (as happend on an episode (or 2?) of Planet Earth.)

Did a test - recode down to 576-line and play upscaled, with barely noticable loss.

Is this just the omnipresent Chinese smog and dim light? Or has the ABC got an inferior version?

But aside from the sharpness it looks great.

[FeOe_Vidz]

It is only 1280x720, which is better than SD, and it's in 5.1, and the weird thing I've noticed is that it's also @ 50fps. I thought that the STB/PVR would have scaled it back to 25fps, or is this just how it works sometimes? I'm glad there are the extra frames to play with as ABC doesn't have the best recording reception here, let alone anything in HD, then with the wind we had the last 2 weeks, it's amazing how good it did turn out.

[ckent]

ABC transmits a show produced in 1920x1080p25 by going through this process:

1920x1080p25 -> 1920x1080i50 -> 1920x540p50 -> 1280x540p50 -> 1280x720p50

The result is an image that is definitely better than SD but gives you some still images that have built-in "wiggle", unless you use an external HD decoder and set the output to 1080i into your HD display. It would be more suitable if their HD service was set to 1280x1080i, since that would consume just as much or less bitrate to give just as much or better quality.

FeOe, there was a delightful in-depth tornado of arguments here in 2006:

http://www.dtvforum.info/index.php?showtop...st&p=443972

CK.

[Neon Kitten]

ABC transmits a show produced in 1920x1080p25 by going through this process:

1920x1080p25 -> 1920x1080i50 -> 1920x540p50 -> 1280x540p50 -> 1280x720p50

Why such a seemingly unnecessary cascade of scaling stages there? Why not go straight from 1920x1080i50 to 1280x720p50? We're dealing with evenly divisible numbers here after all...

And wouldn't dropping to a 540-line resolution at the middle stage there mean there's actually LESS lines of horizontal resolution than SD?

(Edit: just had a glance at the thread you linked to, which seems to go some way towards explaining it. But it still seems kind of silly to me).

[ckent]

Part of the reason is (at a guess) that much of the HD equipment (uncompressed interconnects like HD-SDI, and tape & delivery formats like Digibeta) are in 1080i.

But that doesn't answer your question about going from 1080i to 720p50 ... well obviously it's easier to work on one field of 1080i than it is to interpolate the interlaced frame and derive a 1080p picture first. If you really want a full quality 720p50 picture, you need to work out what the 1080p50 equivalent would be first.

You *are* performing two conversions here, after all. An interlace-to-progressive conversion, and a 1080 to 720 conversion. By doing the second one first, it's a lot easier and requires only half the size frame buffer and half as many pixels to push around at a time.

The whole thing about going from 1920 to 1280 is a little arbitrary ... I spelt it out in detail but it doesn't actually matter at what stage you do it.

The horizontal scaling could make you consider this as 3 conversions in total instead of 2 ... but frankly it doesn't matter.

CK.

[merovingian]

But that doesn't answer your question about going from 1080i to 720p50 ... well obviously it's easier to work on one field of 1080i than it is to interpolate the interlaced frame and derive a 1080p picture first. If you really want a full quality 720p50 picture, you need to work out what the 1080p50 equivalent would be first.

Hang on a second. In your previous post you were talking about going from 1080p25 to 720p50, not 1080i50 (ie. natively interlaced) to 720p50. So there's no deriving of a 1080p signal to be done, because that's what they're starting with.

I don't know that the ABC would do exactly to go from 1080p25 to 720p50, but I would like to think it's not the process you outlined. What you outlined is quite posisbly what they do to go from 1080i50 (ie. natively interlaced) to 720p50 - except without ever having had 1080p25 in the first place.

Getting 1080p50 from 1080p25 is as simple as showing each full 1920x1080 frame twice. And then scaling each full frame from 1920x1080 to 1280x720 to dervice 720p.. I'd like to think that's all their doing when presented with natively progressive HD source.

[ckent]

Hang on a second. In your previous post you were talking about going from 1080p25 to 720p50, not 1080i50 (ie. natively interlaced) to 720p50. So there's no deriving of a 1080p signal to be done, because that's what they're starting with.

OK but it's quite simple: On the one hand, the original material is 1080p25 (on a 1080i50 tape) and on the other hand, the broadcast format is 720p50.

So the bottom line is, that you'll have to derive a 50fps at some stage, if you want to do this properly.

Otherwise you'll just end up with something with half as much detail and a lot of interlace-style flickering, baked into the MPEG stream.

I don't know that the ABC would do exactly to go from 1080p25 to 720p50, but I would like to think it's not the process you outlined.

Yeah we'd all like to think it's not. But when you view two frames of 720p50 up close, you'll see they come in pairs, and they shimmer just like a simple de-interlace (bobbing method) conversion.

(But let's not start all this argument again ... the best place to do it is in that thread I quoted above).

What you outlined is quite posisbly what they do to go from 1080i50 (ie. natively interlaced) to 720p50 - except without ever having had 1080p25 in the first place.

Nah they just have 1080p25 represented in the HD distribution master ... it's 1080pSF25 recorded onto a 1080i50 format.

Getting 1080p50 from 1080p25 is as simple as showing each full 1920x1080 frame twice.

Oh true, but when the source material comes out of the tape or distribution master (which is likely 1080i50), it's probably going along HD-SDI (which is definitely 1080i50) ... so you've already lost your frame dominance. And bang, there goes your "pristine progressiveness". The playout systems don't know if it's 1080i50 or 1080p25 anymore. They could hazard a guess, but that would involve live processing of the HD image and the equipment to do that on HD is still expensive ... it's simpler just to treat it as always containing 50fps interlaced material, and that's exactly what it does.

And then scaling each full frame from 1920x1080 to 1280x720 to dervice 720p.. I'd like to think that's all their doing when presented with natively progressive HD source.

Most of us were blissful in our faith of the TV stations' technical abilities once upon a time.

But the last several years have been quite educational, even to the casual viewer with an HDTV setup, because it's so easy to see how the stations mangle the picture in many different examples. There are plenty of places where news footage (etc) goes through composite feeds ... the country stations sometimes still look like they are producing stuff on VHS ... certain pay TV channels can't even start a brand new network in 16:9, and launch them in 2008 as 4:3 with black letterboxed material whenever something is in widescreen. Until the last couple of years Channel 7 was called Channel 4+3 around here because they were the worst example of this kind of thing.

CK.

Edited May 30, 2008 by ckent

[Neon Kitten]

Most of us were blissful in our faith of the TV stations' technical abilities once upon a time.

But the last several years have been quite educational, even to the casual viewer with an HDTV setup, because it's so easy to see how the stations mangle the picture in many different examples. There are plenty of places where news footage (etc) goes through composite feeds ... the country stations sometimes still look like they are producing stuff on VHS ...

And curiously, shows out of the ABC's Melbourne studio look quite clearly inferior to shows out of their Sydney one. This for some reason looks even more glaringly obvious on the HD channel even with non-HD shows.

A good way to see the difference at the moment is to compare two back-to-back Wednesday night shows. Spicks And Specks, out of Melbourne, looks absolutely dreadful next to The Gruen Transfer, which is (I presume) out of Sydney. Gruen's picture quality is light years ahead - indeed it made me wonder if it was originally produced in HD (I believe the ABC have HD cameras in their Sydney studios, right?)

[ckent]

.

Edited May 30, 2008 by ckent

[ckent]

Well there's a few things off the top of my head, yeah -- (is this the right forum though?) :-)

- ABC's Sydney studios have HD cameras, which will look better even in SD (yes Gruen comes from Sydney)

- ABC1 and ABC2 in Sydney always have some thin analogue blanking on the right-hand edge, probably from an digital -> analogue -> digital path

- With the old two-tone ABC news "worm" logo, ABC Melbourne couldn't even achieve two tones and just superimposed a grey logo over the picture

So yeah ABC Melbourne does have that "uh-oh we're in the bush now" feel about it.

CK.

[Neon Kitten]

Well there's a few things off the top of my head, yeah -- (is this the right forum though?) :-)

Well, we ARE talking about HD. Kind of

- ABC's Sydney studios have HD cameras, which will look better even in SD (yes Gruen comes from Sydney)

Thought so, since a credit at the end of Ten's Good News Week implies that the show is recorded at ABC Sydney - and it's in crisp HD. (There, we're on topic now )

It really does make a massive difference on SD shows. Another case in point is At The Movies versus The Einstein Factor, back to back on Sunday evenings.

[merovingian]

Well I haven't sat there and analyzed any ABC HD broadcast for twitter and the like, so I can't speak with authority. It would hardly surprise me that they would merely bob a natively interlaced 1080i50 signal to produce 720p, much like most 768p TVs. But if my 1080p TV and my HTPC are both independently capable of performing weave deinterlace on 1080p25 pSF in a 1080i50 broadcast, I find it quite bewildering that an organization with the resources of the ABC can't do the same thing in preparing their 720p broadcasts. If what you say is true then the ABC is in fact broadcasting zero genuine HD material.

[ckent]

Yup, pretty much agree with you ... I'd probably be less critical of the 720p "native" broadcasts, but that's because you can still get a very reasonable result out of it if you have an external decoder and set it to output 1080i. You sort of (... kind of ... sometimes) get a result equivalent to 1280x1080i by doing it that way. I'll just say: "It looks pretty good". I watched the Sydney Harbour Bridge documentary that way, and it had a mixture of 1080i50 and 1080p25 stuff in it, and was very very impressed. But on other TVs where I see ABC HD (when it's decoded inside the TV, generally), it looks rubbish. "YMMV", as they say.

As for 768p TVs ... I found that the ones up to 2006 generally had the bobbing problem. Anything designed and released in 2006 was generally doing justice to the 1080i signals it received, and converted it to a very good approximation of 768p.

CK.

[Guest jenniferedwards]

Yes I agree with CKnet

[pneu]

ABCHD seem to be using a better form of de-interlacing now which weaves sections of the frame that are still and bob parts that are moving. Previously they were just bobbing everything.

[pneu]

Yes I agree with CKnet

Spam.

[conphi]

I think they're releasing this program on bluray...

Regards Phil C.

[miata]

I think they're releasing this program on bluray...

Regards Phil C.

It's also airing on FOXTEL HD starting next Monday night. (BBC I think)

[phreek]

ABC news "worm" logo

The ABC logo is an example of a Lissajous figure; a 3:1 ratio of out of phase complex harmonic motion.

Don't ask... a misspent youth on electronics and oscilloscope fun