why is the old resolutions of 1440 x 1080i and 544 x 576.

swoofer

I read the new document and found the following

Picture Quality
The picture resolution for RTÉ Two HD Select will be 1440x1080i. The picture
resolution for the standard definition services, RTÉ News Now, RTÉjr and RTÉ Plus
will be 544x576.

Why are we using these outdated resolutions with a brand new service? Is there a technical reason why? I would have thought 1920 x 1080 was proper HD and 720 x 576 was best for SD?

Am I missing something?

gb--

watty

They are not outdated. The UK is also using 1440x1080i for Terrestrial HD, it's the anamorphic version of "square pixel" 1920 x 1080 HD.

Terrestrial is more limited in bandwidth than Satellite.

Square Pixel 4:3 SD would be 768 x 576. No one transmits it.
Square Pixel 16:9 SD would be 1024 x 576. No one transmits it.
DVB uses many resolutions including 384 x 288p, 544 x 576i, 704 x576i and 720 x 576i, all in 4:3 and also stretched (anamorphic) to 16:9 WS.

It would be nice indeed to have the maximum possible, but that would cost maybe 30% more and eventually require three Multiplexes rather than two. The Government hopes to make €500M selling of TV spectrum.

Why 720 x576 and 544 x576 in DVB and not 1024 x 576 and 768 x576?
Because of compromise with NTSC which is only 640 x480i for square pixel and 854 x 480 (approx) for Widescreen (16:9). The average of 854 and 640 (compromise) is 746, which isn't far from 720. Pixels per line I think have to be a multiple of 16.

Why 1080 line for HD? Why not 576 x2 = 1152 lines Makes more sense for upscalling!

Because HD is based off the old NHK 1125 line hybrid analog HD derived from NTSC.
NTSC 525 lines is 480 visible.
PAL/Secam 625 lines is 576 visible.

It seems a shame That SD is not 1024 x 576 and HD 2048 x 1154, (or 768 x 576 and 1536 x 1152 anamorphic only) to allow for easy upscale/downscale and similar jump in quality.

US & Japan going from analog NTSC to 1920x 1080 HD get much bigger quality jump than we do.

tlaavtech

I have no problem with the 1440x1080 format. That is one of the HD standards. My problem is with the resolution for SD.

SD PAL cameras and graphics work on 720 x 576 resolution. My Avid does not give me the option of 544x576 PAL - It does give me the 1440x1080 and 1280x720 options in HD, but not 544x576. As far as it is concerned, PAL50i is 720x576 period.

So why have they chosen 544 rather than 720? What kind of bandwidth saving is there. I would love to see a side-by-side test for 720 vs. 544 using the same bandwidth. On graphics particularly, the errors produced by converting to 544 are horrible - and I would guess that they are more objectionable than the errors introduced when encoding at 720 using the same bandwidth.

watty

PAL is an Analogue spec.

Your camera and Avid are likely for DVD production. Though DVDs do Support 704 x 576 and 720 x 576.

Why does so much Satellite & Terrestrial World Wide use 544 x 576, instead of DVD/DV 704 x 576 (sometimes 720 x 576)?

Digital Broadcasting is NOT about more quality. Except if it's HD.
It's about
- Delivering mix of 4:3 and 16:9 in same channel
- Saving space to make the Broadcasting cheaper
- Having the picture "as good as" a perfect Analogue feed, without the PAL artifacts (i.e. like S-Video quality).
DVDs are about slightly more quality, so you buy them and not record off TV



Earliest consumer Digital cameras used DV format

Closely following ITU-R Rec.601 standard, DV video employs interlaced scanning with the luminance sampling frequency of 13.5 MHz. This results in 480 scanlines per complete frame for the 60 Hz system, and 576 scanlines per complete frame for the 50 Hz system. In both systems the active area contains 720 pixels per scanline, with 704 pixels used for content and 16 pixels on the sides left for digital blanking. The same frame size is used for 4:3 and 16:9 frame aspect ratios, resulting in different pixel aspect ratios for fullscreen and widescreen video

http://en.wikipedia.org/wiki/PAL

PAL B/G (most PAL) is 5MHz, PAL I is theoretically 5.5MHz.
In pixel terms, the line frequency is 15.625 KHz
= 64 us
but active video is 51.95us
So ratio 51.95/64
divide 5MHz by 0.015,625 MHz = approximately 320 cycles..
if we take alternating black and white pixels as the limit, then 640 pixels.. But only 51.95/64 are visible = 519.5, thus 520 pixels are minimum for PAL B/G
if you want WS instead of 4:3 then without deminishing quality you need 690 pixels (and more bandwidth).
If we take an average of 4:3 quality and what a hypothetical WS 16:9 we get (690+520) /2 = 605 pixels per line.

For PAL I, then 5.5MHz. =352 cycles, approx 704 pixels. But the sync timining means only 285.725 cycles visible, needs 571 pixels.
If we had WS that wasn't anamorphic, then 571/12 *16 = 761 pixels
Average of 571 & 761 = 666 pixels.

But... Most domestic CRTs did not have full horizontal resolution...

So any way they chose 544, which is exactly divisible by 16 or 32 (helps encoders) and is higher quality than PAL-B/G 520 pixels and lower than PAL-I 572 pixels, and happens to be close to the average of them which is 546 pixels (not integer ratio with 16).

I've actually told lies above. As the maths is more complicated. You can actually get somewhat better quality if your camera or film scanner is 1088 x 1154 and you do a re-sample to 544 x 576 (anti-aliasing). DVDs from film is scanned higher and resampled. Such resampling of higher resolution results in less visible artifacts and better picture than a 720 x576 camera, even if at 544 x 576

So 544 x 576 should be better quality than a "perfect" S-Video feed. (Actual PAL without a very clever Comb filter has false patterning on intense colour and false colour on fine detail). It's not actually shabby at all.

Not as good as 720 x 576 DVD. But then a DVD uses higher quality Bit Rate. BD (BluRay) can use nearly twice the bit rate of HD broadcasting!

Broadcasting simply isn't going to use DVD and BD quality.

Assuming encoders etc are unaffected (they are not).
720 x 576 = 414720
544 x 576 = 313344
Extra bandwidth cost is about 31%

1920 vs 1440 extra bandwidth cost is 33%

note that 720 vs 544 is approximately the ratio of 16:9 vs 4:3,
So if in the future the main channels are HD that's a big jump
old 4:3 TV from analogue Tape (even 2" tape), or produced for PAL 4:3 or TV from 16mm film (common for older BBC outdoor work) is hardly even 544 x 576 resolution.

Shopping channels have been known to use 384 x 288

Summary
Digital Broadcast is a replacement of Analogue, not a broadcast version of DVDs and BDs. Only HD is a major increase in quality (only needed for larger screens). 544 x 576 in theory is slightly better than perfect Analogue. Also 544 x 576 in 4:3 is near identical resolution to 720 x 576 DVD 16:9 WS.

1440 x1080i is anamorphic version of 1920 x1080i square pixel HD.

tlaavtech

Please don't take this the wrong way, but the reasons for how we get to our current resolutions is not the point I wanted to make. As you say, analogue and digital are different beasts. (As I read the post I realised how long it is since I got my electronics degree )

For the following example, I will assume a SD programme shot within RTE.

Every piece of equipment from the camera through the Vision Mixer, graphics, tape or hard drive recorder and out to the playout system treats the video signal as a digital signal with a resoloution of 720x576. Why at the transmission stage do RTE discard approx 30% of the picture? I am asking that they keep the same bitrate at the encoder, but encode the full picture.

I can understand the argument that the programming carried on RTE2 (Sport and HQ American drama) will benefit more from the 720 res, rather than the talking heads on RTE1, but I still think that if they kept the bit-rates the same, the picture quality on the other stations would improve because all of the original picture is being encoded.

Having said all that, I am sure that RTE didn't choose 544 just to be awkward, obviioulsy they have done their tests and have taken the decision of lower resolution rather than higher compression.

I just get annoyed by jaggie graphics and I would love to see a comparative demonstration.

watty

It's to save bandwidth.

544 is the only DVB alternative to 704 or 720 that's comparable/better to Analogue.

If you see "jaggies" on a normal TV at normal viewing distance, then the issue is not the 544 x 576 DVB, but the "what ever it is" that generated the graphics.

If you have video editing, compare importing these stills created in photoshop/gimp/Paintshop pro:
unaliased text on a 720 x 576 image
"aliased text" on a 720 x 576 image
unaliased text on a 1440 x 1152 image, "smart" resampled to 720 x 576 image
"aliased text" on a 1440 x 1152 image, "smart" resampled to 720 x 576 image


If you like do some unaliased diagonal boxes etc too..

Author to DVD and play on TV



"smart" Resample all four images to 544 x 576 (not a legal DVD resolution) in photoshop/gimp/Paintshop pro and view 100% on PC.

If you edit video 544 x576 importing those (possible with some free tools) and encode to MPEG2 @ 544 x576 and use a PS editor to "lie" about the resolution (DVD patcher?) then you can author the DVD. It will really be 544 x 576 though the authoring "thinks" it's 720. Though it's legal DVB resolution, it's not a valid DVD resolution, but most DVD players will play it "full screen" at 4:3 or 16:9 depending on yourWS flag setting.

tlaavtech

watty wrote: »

If you see "jaggies" on a normal TV at normal viewing distance, then the issue is not the 544 x 576 DVB, but the "what ever it is" that generated the graphics.

But I am viewing on a projector - effectively a 110" screen, hence my wish for greater resolution for the upscaler to work on. (I never claimed I wasn't being selfish in my wish!!)

It's to save bandwidth.

I know its to save bandwidth, but as I said above if they kept the bit-rates the same, the picture quality would improve because all of the original picture is being encoded - the picture would suffer less from round-off errors.

If you transmit a lower resolution from the original picture you are discarding usefull information. Any resampling/down-scaling introduces errors especially when the new resolution is in the same region of scale as the original i.e. not 25% overall of the original.

watty

You need HD

It's comming.

tlaavtech

watty wrote: »

You need HD

too true

swoofer

Thanks all for great replies and I have to say its great having decent picture quality on all channels now, lets hope these transfer well to hotel rrooms in time as I have been in some hotels and pic quality has been quite frankly a disaster. Roll on that 2nd mux and hurling in HD yippeee.

gb--

Mike 1972

watty wrote: »

The Government hopes to make €500M selling of TV spectrum.

How (and when) was this figure arrived at ?

rlogue

544 X 576 does of course save bandwidth but that does not stop it looking mushy on a 47" screen.

I can directly compare the picture quality on BBC 1 NI on satellite and RTE 1 on satellite. At 720x576 the BBC 1 NI picture knocks spots off the RTE 1 picture. EastEnders is a good comparision to use as the picture quality is noticeably worse on RTE 1 compared with SD BBC 1, let alone the upscaled SD on BBC 1 HD.

Are RTE 1 and 2 broadcast at 544 x 576 on cable?

watty

Cable is worse than Sky
I suspect UPC re-encode

Mike 1972

rlogue wrote: »

I can directly compare the picture quality on BBC 1 NI on satellite and RTE 1 on satellite. At 720x576 the BBC 1 NI picture knocks spots off the RTE 1 picture. EastEnders is a good comparision to use as the picture quality is noticeably worse on RTE 1 compared with SD BBC 1, let alone the upscaled SD on BBC 1 HD.

Interesting you should say that. I was always under the impression that RTE's bitrate on satellite was considerably higher than the Beebs (having 22 odd regional variants of BBC1 doesnt help) If this is the case surely RTE should be able to increace their resolution as well ?

watty

rlogue wrote: »

544 X 576 does of course save bandwidth but that does not stop it looking mushy on a 47" screen.

In fact HD was purely rolled out originally in Japan and US because of larger screens (RPTVs were very popular in US for up to 56" before Plasma/LCD even existed).

Really 37" is max size for non-HD in a typical living room for NON-HD.

rlogue

At the time of writing BBC 1 NI is 4.2 mbit and RTE 1 is 3.2 mbit so a lower bit rate and of course lower resolution.

Mike 1972

Once again I stand corrected. Obviously I was basing it on outdated information

rlogue

But also bear in mind that lower bit rates don't necessarily mean lower quality.

Take Luxe TV for instance - whatever encoder they were using for HD was able to churn out superb pictures on a far lower bit rate than the BBC were using.

The real arbiter of picture quality is the resolution and if RTE are throttling their video at the crap rate of 544 x 576 then no bit rate increase will do much good.

Mike 1972

rlogue wrote: »

Take Luxe TV for instance - whatever encoder they were using for HD was able to churn out superb pictures on a far lower bit rate than the BBC were using.

Which does make the Beeb's contention that reducing their bitrate (HD channel) wouldnt make any difference on account of their nifty, gee-whizz, high falutin new codec rather odd

One thing Ive always wondered was wht the DVB-S spec never included a region autoswitching option in the EPG software so that regionalised channels like BBC1 and ITV could transmit their London feed at a higher bitrate and transmit flags to seemlessly switch viewers outside London beteween the Local and London versions of BBC1 during networked programmes.

rlogue

The BBC reduced the resolution and the difference is significant.

watty

watty wrote: »

Cable is worse than Sky
I suspect UPC re-encode

I compared RTÉ 1 on Saorview a few months ago with UPC's feed and UPC was clearer. Less blurry, so I'd say UPC is in 720x576.

tlaavtech

Karsini wrote: »

I compared RTÉ 1 on Saorview a few months ago with UPC's feed and UPC was clearer. Less blurry, so I'd say UPC is in 720x576.

I don't have much experience of UPC, but I remember seeing it on exactly the same model 32" as I had at home one Christmas night. They were watching one of the Pirates of the Carribean and was apalled at how blocky the picture was - a 700meg DVD rip download would have looked better. I'll take RTE MPEG4 @544 over UPC at 720 any day of the year

lawhec

From my experience, 544x576 SD broadcasts on Freeview look fine (with an adequete bitrate) in 4:3 but it introduces notable blurring in 16:9 material especially on large displays as the pixel displayed is streched close to the ratio of 2:1 - a good comparison can be made between watching Channel 4, which is broadcast 720x576, and Channel 4+1, which is 544x576. I think the majority of Freeview channels are now 544x576, though the five main channels (BBC1, BBC2, UTV, Channel 4 & Channel 5) are either 720 or 704x576 by Ofcom mandate.

watty

See http://www.boards.ie/vbulletin/showthread.php?p=69125321#post69125321 for simulations

Sam Russell

I think that all the main four channels should be broadcast in 720 by 576 as standard if WS as a minimum.

Because studios introduce digital elements in the production process by degrees, we have parts of the signal transformed to digital in isolation with all other parts. The problem with creeping digitisation is the problem of quantisation. The analogue signal may have a horizontal bandwith equivalent of 576 lines but the when digitised, the digital clock defines where those 576 lines occur which may not be where the analogue signal may have them. It is this that gives rise to jaggies. To overcome this, digital signals have to go to higher resolution. The signal should start at 1440 lines and then convert down.

Therefor the digital resolution has to rise to 720 by 576 for all the main channels. It is the least we deserve.

Mickey Mike

I wonder why RTE chose 1080i instead of 1080p? Looking at YouTube they say 1080p is the way to go for better quality.

The Cush

Mickie Mike wrote: »

I wonder why RTE chose 1080i instead of 1080p? Looking at YouTube they say 1080p is the way to go for better quality.

No terrestrial broadcaster up until recently were using 1080p that I know of, not sure of the reason, maybe higher bitrate thus reducing mux capacity, insufficient numbers of 1080p displays in the population to justify its use, lack of source material, studio/playout not capable ???

The recently launched German DVB-T2/HEVC pilot mux transmits in the 1920x1080p50 format but the broadcasters supply their channels in either 720p or 1080i format where it's upscaled by the multiplex contractor for transmission.

STB.

The Cush wrote: »

No terrestrial broadcaster up until recently were using 1080p that I know of, not sure of the reason, maybe higher bitrate thus reducing mux capacity, insufficient numbers of 1080p displays in the population to justify its use, lack of source material, studio/playout not capable ???

The recently launched German DVB-T2/HEVC pilot mux transmits in the 1920x1080p50 format but the broadcasters supply their channels in either 720p or 1080i format where it's upscaled by the multiplex contractor for transmission.

Bandwidth. Interlaced is half the overhead.

The Cush

That reminded me of the discussion Ofcom had with the industry in relation to including 1080p50/AVC level 4.2 in the UK's DTT Reference Parameters back in 2009 prior to launching the DVB-T2 HD mux.

reboot

The Cush wrote: »

That reminded me of the discussion Ofcom had with the industry in relation to including 1080p50/AVC level 4.2 in the UK's DTT Reference Parameters back in 2009 prior to launching the DVB-T2 HD mux.

As Watty and I discussed long time ago, I shot HD for NHK over many years at 1250 lines, at that time there was not a camcorder available, and Panasonic supplied a tape deck on wheels, brick batts needing changing very often and the HD lens loosing focus if tilted too much as the elements moved due to gravity.Editing could only be done in Norway and New York.
Just heard BBC click discuss this week VR head sets getting close to a frame rate of 95, pointing out (according to Frame store) London, that Reality has a frame rate of 95?
Point being we may not be able to tell VR apart from R.