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Old 18-07-2013, 21:08
lotrjw
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Well there really is no point using 720x576 over 704x576 since the extra pixels are meant to be cropped. If using non-standard equipment (e.g. a PC), you can gain those extra 16 columns of pixels if they aren't blank but it's not exactly experience-altering.
yes I wish 704 was the res that channels used or that any SD channel originating in HD would utilise the full 720 columns of SD for a better quality image!
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Old 18-07-2013, 21:26
jj20x
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Well there really is no point using 720x576 over 704x576 since the extra pixels are meant to be cropped. If using non-standard equipment (e.g. a PC), you can gain those extra 16 columns of pixels if they aren't blank but it's not exactly experience-altering.
Non standard equipment isn't really the problem, supposedly standard equipment displaying black bars is. Still, not really a problem for the broadcaster, more one for the manufacturer.. or the purchaser.
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Old 18-07-2013, 21:27
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yes I wish 704 was the res that channels used or that any SD channel originating in HD would utilise the full 720 columns of SD for a better quality image!
Well that wouldn't work. 1920x1080 is 16:9. Once you downconvert that, it's 704x576. Where would the extra 16 columns of information come from? If you downscale straight to 720x576 then the aspect ratio will be wrong.

Although, things get even more complicated because a lot of TVs don't actually adhere to the proper specifications and incorrectly treat 720x576 as 16:9. It's basically a mess and the move to square-pixel HD formats can't come too soon.
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Old 18-07-2013, 21:38
lotrjw
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Well that wouldn't work. 1920x1080 is 16:9. Once you downconvert that, it's 704x576. Where would the extra 16 columns of information come from? If you downscale straight to 720x576 then the aspect ratio will be wrong.

Although, things get even more complicated because a lot of TVs don't actually adhere to the proper specifications and incorrectly treat 720x576 as 16:9. It's basically a mess and the move to square-pixel HD formats can't come too soon.
Too right I agree to that!
the extra padding is a compleate waste then as TVs still need to ignor it to get a 16:9 image which many dont!
if the HD picture was down converted using special equipment to sample the horizontal res at 720 across, then TVs would most likely register that as a full 16:9 image when upconverted on a HD TV.

or better still receivers that upconvert 720*576 to HD should remove the padding so the image can use the full screen area!
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Old 18-07-2013, 22:03
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The worst part is that even broadcasters don't seem to understand how it works. I have some recordings of The IT Crowd from E4 HD and they're all the wrong aspect ratio because they've taken the full 720x576 image (the outer 16 columns of which are usually blank) and made it 1920x1080, rather than just the 702x576 section.

To correct this I have to set the display resolution to 1969x1080 in the MKV container. :/


(Just realised everywhere I've been saying 704 I mean 702...not that a 2 pixel difference in aspect ratio would ever be noticeable.)
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Old 18-07-2013, 22:11
lotrjw
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The worst part is that even broadcasters don't seem to understand how it works. I have some recordings of The IT Crowd from E4 HD and they're all the wrong aspect ratio because they've taken the full 720x576 image (the outer 16 columns of which are usually blank) and made it 1920x1080, rather than just the 702x576 section.

To correct this I have to set the display resolution to 1969x1080 in the MKV container. :/


(Just realised everywhere I've been saying 704 I mean 702...not that a 2 pixel difference in aspect ratio would ever be noticeable.)
how do you set that 1969*1080? and in the document http://www.etsi.org/deliver/etsi_ts/...54v011101p.pdf which was mentioned it reads:
NOTE 3: It is recommended that luminance resolution of 704 pixels represents the "middle" of the picture, and that
it be decoded to a 720 pixels full-screen display by placing 8 pixels of padding at each side. It is
recommended that luminance resolutions, such as 352 pixels, that are natural scalings of 704 pixels, be
upscaled to 704 pixels and padded as above. It is recommended that all other resolutions be scaled as
indicated by the table above. Where this does not result in the expected 720 pixels full-screen display, it is
recommended that the result of the scaling be clipped or padded symmetrically as required to produce a
720 pixels full-screen display.
So it mentions 704 not 702.
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Old 18-07-2013, 22:11
jj20x
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(Just realised everywhere I've been saying 704 I mean 702...not that a 2 pixel difference in aspect ratio would ever be noticeable.)
Let's just go back to saying 704.
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Old 18-07-2013, 22:12
jj20x
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So it mentions 704 not 702.
You got there first.
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Old 18-07-2013, 22:14
lotrjw
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You got there first.
lol never mind
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Old 18-07-2013, 22:20
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...Which I can do now without spending any more brass on DSO, thanking you kindly.
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Old 18-07-2013, 22:33
lotrjw
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...Which I can do now without spending any more brass on DSO, thanking you kindly.
when the 700Mhz band is cleared the com MUXs apparently would have to go DVB-T2 to survive! or they would seriously loose coverage, pushing lots of people onto freeview lite, who would want that?

DVB-T2 is the only way to go treat the next 4 years as a time to prepare for DSO part 2 and get yourself freeview HD receivers to replace any SD only ones in that time! Remember HD receivers can output all channels in SD too for old equipment!

When DVB-T2 is the only standard in the UK for DTT you can be sure there will be plenty of SD channels on there.
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Old 18-07-2013, 22:35
kjhskj75
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all HD receiving boxes have a Scart or composite output on them with HD channels downscaled for that output! So anyone with an old SD set will still be able to watch in SD! where there might be a issue is with any boxes that dont have RF output in analouge SD, but some boxes should do that still!
But is there a rule that says they have to have scart ?

I own a bluray player that only has HDMI and SPDIF, no analogue outputs at all.
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Old 18-07-2013, 22:41
jj20x
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But is there a rule that says they have to have scart ?

I own a bluray player that only has HDMI and SPDIF, no analogue outputs at all.
Because copyright protection doesn't work with SCART, but the subject was about downscaling HD TV to view on legacy equipment.
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Old 18-07-2013, 22:41
lotrjw
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But is there a rule that says they have to have scart ?

I own a bluray player that only has HDMI and SPDIF, no analogue outputs at all.
thats bluray its totally different as it doesnt receive over the air transmissions or Dcab

I would say all Dcab, Dsat and DTT HD receivers would have to have an analouge output such as scart or phono, if not then it would be a very bad box not have that capability!
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Old 18-07-2013, 23:13
gomezz
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I own a bluray player that only has HDMI and SPDIF, no analogue outputs at all.
Not even component or composite?
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Old 19-07-2013, 01:15
DragonQ
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Let's just go back to saying 704.
704 is used because it's a multiple of 16, which is useful/necessary for digital video encoding, but strictly it's supposed to be 702 (I think this is to do with the old analogue system, can't remember exactly). Either way it doesn't matter, taking 702 or 704 as the "active area" makes negligible difference. If encoding 16:9 PAL video, you should really use 704x576, not 720x576.

how do you set that 1969*1080?
You can write whatever aspect ratio you want in the container metadata of MKVs. I use MKV Merge.

A slightly better solution would be to crop the outer 16 pixels but that involves re-encoding, which I avoid.
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Old 19-07-2013, 02:40
jj20x
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704 is used because it's a multiple of 16, which is useful/necessary for digital video encoding, but strictly it's supposed to be 702 (I think this is to do with the old analogue system, can't remember exactly). Either way it doesn't matter, taking 702 or 704 as the "active area" makes negligible difference. If encoding 16:9 PAL video, you should really use 704x576, not 720x576.
Yeah, the reason I said lets just go back to saying 704 is simply because 704x576 is what is actually used. It's a little beyond the scope of this topic to start delving into ITU Rec 601 and getting into a discussion of 702.9 non-square pixel widths.
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Old 19-07-2013, 07:23
technologist
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But is there a rule that says they have to have scart ?
.
The D book ... which has been one of the great contributors to the success of DTT in the UK-
backed with rigorous testing and crowned by the award of the Freeview(HD) tick .
Which is why BIS needs to remove its approval for Freeview equipment

- ticking Freeview HD. only.
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Old 19-07-2013, 08:01
lotrjw
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The D book ... which has been one of the great contributors to the success of DTT in the UK-
backed with rigorous testing and crowned by the award of the Freeview(HD) tick .
Which is why BIS needs to remove its approval for Freeview equipment

- ticking Freeview HD. only.
thanks I wasnt sure if it was definitive about having a scart on freeview HD boxes, does there have to be one on freesat HD boxes, Sky boxes and Dcab HD boxes too?
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Old 19-07-2013, 08:08
mossy2103
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A box to downscale HD channels?
Or even use then scart connection on any HD box .....
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Old 19-07-2013, 09:43
kjhskj75
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Not even component or composite?
Not even them.

I think HD component analogue for Bluray is more or less banned nowadays.

And who'd want to watch blurays on composite video ?
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Old 19-07-2013, 09:50
technologist
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thanks I wasnt sure if it was definitive about having a scart on freeview HD boxes, does there have to be one on freesat HD boxes, Sky boxes and Dcab HD boxes too?
Sky and DCAb - that is their commercial decision - and as more TVs have HDMI ... these boxes may loose SCART -
BUT these boxes are usually on the main TV only - which is mots likely to be a larger newer flatter panel - and thus be HDMI equipped
But others will make HDMI to SCART down conversion boxes ( but they are a bit complex= not very very cheap)

Given Freesat's Shareholder one may expect that at least one of them would encourage SCART
..... But again may be on main tvs more than others ...

Freeview equipomenst is used on all the other 2 to 3 TVs in the house - and some may be older!!!

BUT ..... at some time SCART will go (just as UHF Modulators have ).. particularly Analogue PAL
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Old 19-07-2013, 10:00
lotrjw
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Sky and DCAb - that is their commercial decision - and as more TVs have HDMI ... these boxes may loose SCART -
BUT these boxes are usually on the main TV only - which is mots likely to be a larger newer flatter panel - and thus be HDMI equipped
But others will make HDMI to SCART down conversion boxes ( but they are a bit complex= not very very cheap)

Given Freesat's Shareholder one may expect that at least one of them would encourage SCART
..... But again may be on main tvs more than others ...

Freeview equipomenst is used on all the other 2 to 3 TVs in the house - and some may be older!!!

BUT ..... at some time SCART will go (just as UHF Modulators have ).. particularly Analogue PAL
Ok so if people want Sky, Dcab or freesat boxes with a scart/analogue PAL output they need to get in there quick before the likes of Sky, virgin and BT and eventually freesat remove this feature? but with freeview HD its part of the specs for the freeview HD digital tick? meaning it will remain I guess?
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Old 19-07-2013, 10:07
technologist
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Yes because of the use of Freeview HD boxes - they are likely to be connected to SCART equipped Displays
- while The pay platforms are far more likely to be plugged into a HDMI equipped TV ... (and the platform operator needs to keep the price down!)

The death on analogue composite video is likely to happen first ...
But at some point SCART will be removed from the Freeview HD spec..... and may be HDMI be - because there is something better!!
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Old 19-07-2013, 10:09
gomezz
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Yes because of the use of Freeview HD boxes - they are likely to be connected to SCART equipped Displays
Are they? More so than pay-TV service boxes?
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