´óÏó´«Ã½

Andy,

Thanks for the answer and your time, however I am a little confused! (not too difficult!)

I am probably missing the point but,

To prevent aliasing I would expect the signal to be very steeply filtered above the nyquist frequency at your end.

I presume the filters you are applying are sloping off at 25MHz, hence it being less bright and your comment "you will also get some (but not all) of the 5th (25MHz) grating."

As you say "theres nothing there" at 30MHz.

If there is no signal there to aliaise, then why is it not just a grey block?

So my next question, is the alias generated at your end or mine? Is the 30MHz grating being completely filtered out?

thanks

ps- it is a full hd screen, so no scaling involved.

.

Thanks Andy and the R&D dept.

Your answer has confirmed my (fairly basic) understanding of digital sampling and filtering theory.

Without having ever seen a (pre-broadcast) professional broadcast monitor it can be difficult for the end user to know exactly what the testcard or any other material should look like.

Just for info I use very low levels of sharpness as I particularly dislike an over edge enhanced and noisy image!

It's a shame TV manufacturers don't provide a "calibrated" preset which has correct frequency response, gamma and colour space etc.

With digital transmission and HDMI as a connection format the variation between input sources should be minimal. Of course some viewers will still prefer their "dynamic" preset !

Andy,

Sorry another awkward question.

Although not perfect, sometimes see macro blocking and artifacts on the most demanding of material (last choir standing on the preview loop), to me the majority of the time ´óÏó´«Ã½HD picture quality is very good.

There is however one an effect that I noticed on a number of programs that I do find very distracting and irritating - motion blur and smear.

I don't believe it's due to the transmission chain but some production method / technique / issue.

Two programs that immediately spring to mind are Doctors and Bonekickers. I also noticed it on few scenes in Being Human, but these were very few and far between and really barely noticeable.

When I say motion blur I don't mean the inherent judder of 24 film or 25 psf video (I can usually tell the difference between I or P source material).

When stationary objects are fine, but a quick head movement, somoene walks past quickly, car drives past can turn into a blurry mess.

I don't believe it has anything to do with my set-up, it's only specific programs. Also I have seen the same effect on other TVs and Doctors even shows this on the SD transmission.

Any comments?

Well there is no accounting for taste! Give me judder over blur any day!

It would be interesting to see what other people think.

thanks

Hi Andy,

After using your tuning guide and the test card the results are excellent.

One of the problems for consumers is getting the best out of HD as often new televisions are set on a default setting which isn't the best setting.

Most televisions now come with various picture options like theatre , normal and other names.
Would it not be possible for the TV industry to go through every panel and find its 'perfect' HD setting using the testcard and save it as an industry standard 'HD picture mode' in the picture selection menus.
Ideally it should be the default mode for when a TV is purchased.

Oviously it's not your responsibility in terms of funding it or even doing the tests, TV companies can easily do that themselves, but the ´óÏó´«Ã½ has led the way by working with them with other technology and making sure consumers get the best use out of it.

I think it would be a good idea at the next HD technical conference.


Also if you have the time.
Can you agree with the statement that -

Eurosport HD and Channel 4 HD upsaled content is of a higher standard compared to the standard definition version of these channels.

Obviously you have to measure various differences but I beleive the overall image on both services is better but that's a view rather than anything scientific.

This is linked to the ´óÏó´«Ã½ decision for now not to run ´óÏó´«Ã½1,´óÏó´«Ã½2,´óÏó´«Ã½3/C´óÏó´«Ã½,´óÏó´«Ã½4/CBeebies on satellite , in DVB-S2 and MPEG 4 and on cable in MPEG-2 and upscale all the programming like Eurosport HD and Channel 4 HD does.
They also insert HD programming on the channels when and where it is avaliable.
Both channels aim year on year to increase the number of hours of HD and reduce upscaled content.

Thank you.

Andy,

Everything SD that I have seen upscaled by the broadcaster and transmitted on an HD channel looks better than it's SD counterpart on an SD channel.

I think this is more to do with the low bitrate mpeg2 transmission on SD V mpeg4 high birate (for SD) on HD channels.

Less to do with the scaling. However I do find it hard to believe that a broadcast quality scaler won't do a better job than you average TV.

Andrew, I actually believe it would be quite simple for the TV manufacturers to include a "calibrated" preset. Although this won't be perfect as each set will vary slightly, it will be a lot better than the current situation where people leave their sets on "dynamic - impress in the shop" setting.

Users can then tweek away from this setting to suit their personal tastes if desired.

tagmclaren,

According to this site,



Channel 4 SD is transmitted on satellite with only 544 pixels or 3/4 of the normal resolution. So assuming the up-conversion is sourced from the full SD signal it's not surprising it looks better!

These sites don't seem to be able to give this info for encrypted SD channels, but it's a fair bet that C4 are not alone in this.

So channels such as ´óÏó´«Ã½1/2/3/4 that are transmitted at full resolution would not show as big an improvement if upscaled although they would still be better.

It was interesting on the recent Welsh snooker to compare ´óÏó´«Ã½2 Wales with the same pictures upscaled on Eurosport HD. The Eurosport version was visibly better, particularly the chroma bandwidth which made the colours of the balls on the wide shot much clearer. Unfortunately the commentary was not up to ´óÏó´«Ã½ standard IMHO! I did try using 2 receivers to get the Eurosport pictures with the ´óÏó´«Ã½ sound, but sadly the Eurosport was delayed by several seconds...

I wasn't actually referring just to ch4.

The snippits of upscaled sd you get on the ´óÏó´«Ã½ also look better.

You expand from the real point I am trying to make which is the SD transmission chain is simply not up to scratch - even the ´óÏó´«Ã½s.

Macro blocking, mosquito noise are all to evident.

Mind you SD was never designed or intended to be watch on 42" + screens.

If SD was broadcast at decent bitrates, or perhaps the current rates with mpeg4, then I might agree with Andys assertion that more often than not it looks about the same.....but thats not what I have experienced so far.

The main problem with SD channels is they are run on stupidly low bit rates and are usually on transponders which are crammed with lots of other channels. Take ITV for example - ITV accross the board is simply awful. I believe they are running at bit rates even less than SD rate???

A good example to use which shows that SD will be better with more bandwith and running upscaled on an HD channel is the Snooker.

Take the recent Welsh open, The Masters and UK championships - all broadcast by the ´óÏó´«Ã½. YES ´óÏó´«Ã½. It was available upscaled on Eurosport HD and the quality was far far higher on Eurosport HD.

On the ´óÏó´«Ã½ version there was lots of blurriness around the balls and when the balls were moving its poor to watch. Watch on the eurosport HD channel (´óÏó´«Ã½s feed) and the quality is fantastic.

Also compare Deal or no deal on CH4 SD to channel 4 HD. Difference is night and day.

@andyquested

Thanks for your reply Andy, in light of the fact it would be difficult to help set up each tv 'correctly' while it is being produced could the ´óÏó´«Ã½ at least run the test card and perhaps some on screen instructions on how to change the image before it starts transmission.
At least then viewers on all platforms can make sure the tv they own is adjusted to perform at its best rather than on a standard setting which often isn't the best setting.

I would argue broadcasts on Eurosport HD or Channel 4 HD looks at least the same, slightly better, or much better upscaled than on the same standard definition channel.
Commercial upscalers used by broadcasters, and greater bandwidth for each of these channels both play a part.

In the long term the ´óÏó´«Ã½ Trust can't argue that all HD channels must always be in HD as all ´óÏó´«Ã½ channels repeat content that wasn't filmed in HD, even Dr Who or Top Gear hasn't been filmed in HD.

If the ´óÏó´«Ã½ channels were to move into HD as I have mentioned before then it would encourage more HD content to be produced as well as allowing current programmes to be upscaled benefiting all HD viewers.

Also considering that on site production teams can output coverage in HD and surround sound is there any reason why the 6 nations currently omits the latter?

Thank you.

Watched a recording of the Kevin Whately Who Do You Think You Are last night.

I thought the motion blur was appalling. Very distracting and spoiled my enjoyment of the program.

HD? Yes, but only when things are stationary.

Andy,

You say you try to ensure that shutter speeds are correctly set.

Any reason why you could not make it specified as a requirement in the ´óÏó´«Ã½s commissioning documentation?

Items such as camera gain are mentioned to keep noise to a minimum.

Thanks for the answer Andy,

It's simply a case of myself finding the effect of blurring motion very objectionable and certainly not in the spirit of HD production.

I don't mind most "artistic" effects chosen by directors. Most work well even in the context of HD production.

I don't think, like some people, everything HD should look like a sharp 50i studio video for example.

BUT motion blur isn't appropriate and I firmly believe it should be minimised as much as possible.

Andy,

Just a footnote to my comments about motion blur.

I watched another episode of Doctors last night.

It's not a program I actually watch very regularly, but it didn't show the significant levels of blur that I had seen on the first few episodes broadcast on ´óÏó´«Ã½HD.

So, something appears to have changed.

Andy: Posted here as the only way I am aware of contacting you.

Is there any Technical reasons why England v Scotland not broadcast in 5.1 sound or is this to be the norm now (money, ´óÏó´«Ã½ HD do not believe it adds value, ?)

Thanks Andy.

As you can see I value 5.1 sound as another dimension to the HD experience. I found the HD picture quality for England and Wales matches excellent.

Thanks to all concerned.

Upscaled channels look much better, mainly due to using mpeg4 and a high bitrate compared to mpeg2 and a low bitrate. Its a shame Formula1 isn't being broadcast upscaled on ´óÏó´«Ã½HD with HD studio cameras, would be far better:(

The ´óÏó´«Ã½S response to new encoders, the bandwith and viewing figures suggests to me that people wont be keeping their jobs for much longer on ´óÏó´«Ã½ HD.

Well I don't agree at all. What other mythical HD services these people in surveys were watching I don't know. However, I am extremely happy at your post as it hints that new encoders aren't a horrifically long time away. At which point if they perform well on the same or slightly lower bitrate I will be extremely happy and the first person to say so. That would be as good news as say other big developments like moving beyond the 9hrs or certain top shows getting into HD.

As I have said a number of times before, although I don't think the ´óÏó´«Ã½HD picture quality is perfect, on demanding material you can see macro blocking, other compression artifacts and sometimes noise, it is not as bad as some of the extreme commentators on these blogs/forums make it out to be.

I can see problems on lots of channels, not just ´óÏó´«Ã½, especially when I get close to the screen but at normal viewing distances are they that bad?

Instead of shouting bitrate, bitrate, sack people, bitrate, would it not be more useful and productive to feedback to Andy problems that you perceive with a particular program. Give a specific, where possible technical description.

For example, I think I see noise especially in the deep red (but also other colours) set backgrounds on Jonathan Ross. Is there a studio / camera issue?

or, I think I see macro blocking on XXXX program. Apart from effects in the general picture , it's easily given away by the effect it has on the ´óÏó´«Ã½HD DOG (lettering edges not clean/shakey/blocky).

This way the ´óÏó´«Ã½ can identify what viewers find particularly objectionable and concentrate on dealing with it.

They can confirm if the problem is in the source material/camera/studio or transmission chain (including encoder), or (you won't like this) may even lie at the viewers end. Some TVs have an appalling detrimental effect on picture quality with dodgey picture processing. Not to mention poor set-up.

Lastly what do people think defines good picture quality?

How are assessing PQ at home? What do you do? Just curious.

Theres no problems with my TV as pretty much all the other HD channels are perfect. I admit some things on the ´óÏó´«Ã½ look good. But its only the shows that go easy on the encoders and require little bandwith.

I know Andy says bandwith has very little to do with quality, but I challenge him to up the bandwith back to what it was when the channel was a trial. Why did the channel look stunning back then yet as soon as it reduces bandwith it doesnt look as good??

Oh yes silly me I forgot lol. The ´óÏó´«Ã½ production were given orders on the day the bandwith was reduced to totally change how the shows are produced to make them look poorer. Sarcasm detected here people.

Prove to us all then Andy its not bandwith and have it upped for a few days. If you are right and the reduced quality is simply production, then youve nothing to worry about in upping the bandwith.

And just for the record channel 4 HD is not as good as it was recently either, so not just the ´óÏó´«Ã½ I have problems with.

I'll try again.

Please explain what problems with the ´óÏó´«Ã½HD picture you find objectionable.

You might find we agree! Again ´óÏó´«Ã½HD isn't perfect, but I don't understand why you feel so strongly that it is so poor, and I would like to find out why.

What size /make /model of screen are you using? If it's much larger than mine it might make defects more obvious depending on viewing distance.

Humax V Sky box????? What effect there. Does the humax broadcom chipset perform block noise reduction?

Oh by the way Andy is absolutely correct. How the encoder goes about performing it's compression is more important than the absolute bitrate. Hence mentioning the toolsets used. This is backed up by the fact that other broadcasters are using lower bitrates to acheive a similar perceived picture quality.

Also productions have a huge variation in picture quality. Care needs to be taken to differentiate between whats in the original source material and effects introduced by the transmission chain.

Camera noise is a prime example. Should a transparant encoder filter it out?

I shall also try again and explain that every single other HD channel is absolutely spot on. Its the lack of detail, the fact pictures do not stand out like they did, the fact that so many shows have artefacts showing, fast moving shows cannott seem to have lots of artefacts especially. The list goes on. Darker scenes look awful.

I was lucky enough to see the ´óÏó´«Ã½ HD channel under test. It was a stunning channel. (with the currect 42" toshiba may i add).

If you guys genuinely believe that a bandwith increase will have no effect what so ever in quality then wheres the harm in trying hey??

I just wish people would cast there minds back to when ´óÏó´«Ã½ HD was running at around 19mbps on the trial......

I too see artifacts on some material, but ´óÏó´«Ã½HD does not have a lack of detail compared to other channels. I would challenge that statement, but I don't want to say you are wrong. There could be genuine reasons as to why we see different things. There is a difference between sharpness and resolution for example.

Can I ask you to check something?

If you have a recording or next time you see the ´óÏó´«Ã½ test card have a look at the frequency gratings (see the top of the thread). What does your tV show. Post a picture if you can. This will give some indication of the level of fine detail it can resolve.

What resolution is the screen? LCD or Plasma

Also describe precisely what is wrong with dark scenes. Apart from programs that have low light induced camera noise I haven't noticed anything particularly wrong. But if you tell me what you are seeing and on what programs I can look for it.

You mention the ´óÏó´«Ã½ trial with the old encoders.

Again there could be a good reason why they looked different. I never saw it so I can't comment.

One way to make the encoders job easier and reduce motion induced artifacts is to filter detail. Could also lead to a very clean noiseless image, but less detailed.

A lot of TVs cant even reproduce the broadcast detail.

Remember bit rates are only going to go down.

Also, you say that every other channel is spot on... I took a close look at a recent ITVHD program.... it showed some artifacts. Clean and sharp absolutely yes, more detail than ´óÏó´«Ã½? No.

Surely the ´óÏó´«Ã½ Technology department can't deny that DVD-S2 with the latest MPEG-4 encoders would provide a vastly superior HD service?

Oviously the current equipment should be used for as long as possible but the next set should surely be based around DVB-S2 and the latest MPEG-4 encoders.

Freesat really needs ´óÏó´«Ã½1,2,3/C´óÏó´«Ã½,4/CBeebies to go HD/Upscaled.

Channel 4 is seemingly happy to remain only avliable via Sky HD boxes and ITV and Five face various financial issues that will limit for some time what HD content is avaliable.
And its unlikely any other free HD sources will become avaliable in the near future.

Andy,

Can you expand/clarify on this part of your last post?

"We take very seriously our responsibilities to our audience and have been working to make sure the new encoders will deliver the full range of services we are obliged to offer at the highest possible quality."

Just curious about the "full range of services" means.

Are there more services to come? Channels or interactive services which you will need to reduce the bitrate to fit them in?

Thats not a potential whinge about reducing bitrates by the way, more curious about the services.

See my question on the other thread re:red button.

Enjoy the time off. In the meantime decent additions to the service.

Andy,

something you might want to check out. I was watching the latest preview loop at about 3.55 am Sunday morning (yes sad I know but jet lag induced disturbed sleep) when the audio sync test came on. Although the sound was continuous the video paused a couple of times.

Fairly sure it was not any problem at this end, never seen the system do that before.

I didn't notice any problems with other sections of the preview loop.

Andy,

Another one of my techy questions I'm afraid.

I was having a discussion with someone regarding the merits of 1080i V 720p broadcasting.

Now, when broadcasting 1080i but the source material is progressive, i.e.film or 25psf video I asserted that if the plasma/lcd deinterlaces correctly the two fields will be woven together to losslessy recreate the full 1080 resolution.

Is this correct?

However, I have read that some broadcasters filter the resolution (typically by a factor of about 0.7) to reduce interline twitter when viewing on a crt thus negating the advantage of 1080 lines. Considering that domestic consumers don't use HD crts I was a little dubious about this fact.

Does the ´óÏó´«Ã½ do this filtering?

The temperal benefits of 720p 50 are obvious however, do you see the ´óÏó´«Ã½ ever moving toward a higher framerate?

Considering a progressive format is easier to compress that interlaced, would the data rate for 1080p50 be too great to be practical?

wish this had a spell checker...temporal....

Hi Andy,

I've just had a first look at content on iPlayer 720P - South Pacific - Series 1 - Episode 1. (Sadly there's not very much at the moment, but I guess this will improve with time.)

It would be interesting to know what technology is used to go from the original material, (presumably 1080i or 1080SFP ), to the 720P / MPEG-4 stream.

Thanks for any info you can provide,

Maurice

I can't imagine why you'd be nervous... Thanks for the plug ;-)

I wouldn't say the 720P iPlayer material I've seen is the finest, sharpest material ever, but bearing in mind the bit-rate it is pretty damn good!

But I do wonder if there is any scope for improved perceived resolution / sharpness, and whether the limiting factor is the compression, or the 720P conversion, or even the source material?

Andy, still here? Anything interesting happening / new blogs coming?

Thanks Andy!

Andy,

Have there been any changes of late to the encoding / transmission chain of ´óÏó´«Ã½HD?

Without going into detail, I think I have perceived some changes in the picture quality generally.

This of course could be the product of:-

A delusional mind
Too much vino
A shift in my equipment...phnar phnar....no, I am referring to my plasma....