Comments on: PAL D1/DV Widescreen square pixel settings in After Effects (CS4 vs CS3)

By: Vikrant Batra

Vikrant Batra — Sat, 10 Dec 2011 08:07:20 +0000

Dude,

Thanks a ton, I know now that I wasn’t crazy that I noticed , 720*576, 768*576, 1024*576 and 1050*576

Vik

By: Mike

Mike — Wed, 05 Oct 2011 21:39:25 +0000

Thanks for the comments Dejan.

You say the 18px “represents a part of blanking line time”. But remember those are TV (non-square) pixels. We’re not really adding anything more, just making the appropriate adjustment for square (ie computer) pixels.

By: Dejan

Dejan — Wed, 05 Oct 2011 20:11:25 +0000

&181;s – should be micro seconds

By: Dejan

Dejan — Wed, 05 Oct 2011 20:06:25 +0000

Good explanation and reasonable from some point of view. To my opinion Adobe made a mistake.
When converting analog video to digital 13,5Mhz sampling frequency is used. Analog video line is 64&181;s “long”. Only 52&181;s is active (just picture, without blanking). Therefore digitized video would be 702px “long”. According to ITU-R 601 digitized video is 720px, which is 53,33&181;s and 18px more. So we are already digitizing more then just active line. Those extra 1,33&181;s (18px) represents a part of blanking line time. I don’t see any sense to add some more pixels. And if you do add 20px to “square-pixel” width (768 -> 788) then pixel aspect ratio would be 4.1026:3.

My question here is why did Adobe did this? Is it because of mistake equipment manufacturers made and it’s some kind of compensation?

How I’m dealing with this issue in “square-pixel” application and Adobe workflow? Simply adding this extra 20px on left and right and 15px on top and bottom so my frame is 788×591 px (4:3) and 1050×591 px (16:9) to stay with my perfect shaped circle. I know some clipping occur on top and bottom and some KB or MB are added to my file, but it’s better than black stripes on left and right or even streching.

By: BarryW

BarryW — Sun, 26 Jun 2011 18:58:18 +0000

Yes, the BBC commissioning page was quite useful for explaing this to people.
There’s also the odd problem of 544 and 704 width DVB.
Channel 4 uses the 704×576 standard with what apears to be 1 pixel each side.
The 544×576 (used by most satellite encrypted SD channels and More4) is a bit of a mystery. I’ve found that if 16 pixels are removed left and right and 10 pixels removed top and bottom a circle looks reasonable circular.

By: BORJA AZÚA

BORJA AZÚA — Thu, 26 May 2011 09:23:41 +0000

excelente documento, a partir de ahora habrá que utilizar 1050 en los proyectos para que pantalla esté full del todo. Gracias.

By: Raymond

Raymond — Sun, 13 Mar 2011 20:27:39 +0000

Hmm, really worth article for me

By: Paddywack

Paddywack — Sat, 05 Mar 2011 17:07:43 +0000

I started getting 1050 Quicktimes from a graphic designer and was both horrified and intrigued! Found this blog and I am slightly less confused than I was.
Just started a thread on the Avid forum about this to see if anyone has any insight in to how Avid handles this.
http://community.avid.com/forums/t/94497.aspx

By: Juan Sanz (Spain)

Juan Sanz (Spain) — Mon, 28 Feb 2011 14:19:08 +0000

Hello, first of all escuse me for my poor english.
I think that 1050 x 576 pixels only is correct if the pixel aspect ratio for TV PAL is 1,094, but it must be only in modern video cards.
Whith the video cards that I work usely, only the values of 1024 x 576, converted to 720 x 576, creates perfect circles recorded in VCR and then rotated in DVE´s. Probably because its internal pixel aspect ratio is 1,067…

On the analogy of this, only 768 x 576, converts to 720 x 576, results in a correct circle, and not 788 x 576 pixels.
I´m I wrong? Thank you.

By: Wrisley

Wrisley — Sun, 12 Dec 2010 17:54:28 +0000

Good blog. Totally agree with you.

By: Emile Hiemstra

Emile Hiemstra — Tue, 07 Dec 2010 20:23:35 +0000

Hi Mike,

Thanks for your thoughts on my question, I’ll put it in my hand-luggage for future videotrips! I’m quite new to AE and the size-change surprised me a little, but now I know where it’s based upon. Thanks again!

Greetz,

Emile

By: Mike

Mike — Mon, 06 Dec 2010 23:07:19 +0000

Hi Emile!

Thanks for the happy comment!

Good question too – well, I tried to answer that a while back but I’ve just been thinking about this again, and I’m not sure it’s quite that simple.

Here we go… just thinking out loud…

Let’s say your NLE can only function using 1024 pixel wide images. Those 1024 images are still going to be squashed down to 720 at some point… So I’d say it pretty much depends on how the NLE in question handles that 720 conversion.

(Scenario 1)
If it just takes all the 1024 pixels and squashes them down to 720 then when it gets broadcast and re-adjusted for viewing on a wide-screen monitor it will still be needing those extra pixels. So perhaps what you should be doing is building everything at 1050 in Photoshop or After Effects but do your final (pre-edit) output at 1024. Basically do a little squash (not a crop) down to 1024 before you start editing. This way you’d hope that the 702 centre pixels (of 720) contain the information from the centre 1024 pixels from the original (1050) image.

(Scenario 2)
But I wouldn’t rule out the possibility that a particular NLE has been designed to add those extra pixels itself (by adding black maybe?) *before* doing the 720 conversion. In which case you should still be building everything at 1024. (Or at 1050 and then *cropping* to 1024 before it hits the NLE).

Phew….

Either way, I’d say there’s no harm in building all your source material at 1050 – at least that way you have the option of cropping to 1024, squashing to 1024, or leaving it at 1050.

By: Mike

Mike — Mon, 06 Dec 2010 22:44:05 +0000

Hi Blazej,

Thanks for that. It made sense in the end I hope.

Incidentally, further down in the link you quoted from is this:

“It means that the sampled horizontal range of the signal is a bit wider than the actual active image frame:
* On 625/50 systems, only the centermost 702×576 pixels (of 720×576) belong to the actual 4:3 (or anamorphic 16:9) frame.”

Which is pretty much the whole thing in a nutshell.

Cheers,
Mike

By: Emile Hiemstra

Emile Hiemstra — Mon, 06 Dec 2010 20:35:12 +0000

Hi Mike! I must say it’s very funny to see people actually have been pumping adrenaline in their systems… Djeez, so much anger About the main post: thank you very much, i guess the truth is out there! Still one question remains: is it right to understand from your explanation that: when creating widescreen graphics for SD in Photoshop I should design something sized 1024 x 576 inside a 1050 x 576 psd? So, when flattened, the extra 13 px on each side squeeze my picture into right proportions, even if my nle or AE version doesn’t use 1050 but 1024? It’s very interesting, whatever people say. These days SD is still the main thing when it comes to broadcast, but i’m looking forward to HD-Empire Thanks Mike, keep up the good stuff…

Some more Dutch greetings!

Emile

By: Blazej Floch

Blazej Floch — Thu, 02 Dec 2010 15:16:35 +0000

Reading my comment is confusing so here what I mean:

Sampling / Digitalizing
702 -> 768 (ITU-R BT.601 conform)
720 -> 788 (with the same method)

So to create conform imagery
768 -> 702 (if black stripes are added)
788 -> 720 (so the 702 area has perfect aspect)

Which is totally what you said in your post. Thanks again