PAL FullD1 Preview is 786x576, should be 768x576

Emulgator wrote on 12/6/2008, 7:23 AM

Hallo to everyone in the forum, my first post here.

Coming from Premiere, Editstudio, Edius, DVDLab to Sony Vegas and DVD-A
I wonder why Sony apps (Vegas, DVD-A) offer SD 4:3 previews of 786x576.

Every other software has 768x576 for Full D1.

While working on Full D1 4:3 projects in Sony apps I get to see a preview window
with a side ratio of ~1.364 where I expect to see 1.333.

PC Preview ARs should be made to be presentable in Square PixelAspectRatio.

We keep the number of lines in PAL as 576.

In Full D1 the 720 sampled column pixels will have to be stretched horizontally
to 768 pixels using a PAR of 1.067
to achieve an aspect ratio of 1.333 (4:3).

In BC D1 704 sampled colums will have to be stretched horizontally to the same 768 pixels using the already available PAR of 1.0926
to achieve the same aspect ratio of 1.333 (4:3)

If these are stretched to 786 pixels we get an aspect ratio of 1.364
and this is what I could measure using a ruler on my (unstretched)
TFT screen and this is wrong.

SONY seem to assume Broadcast D1 as the only choice
but this would only apply to BC-D1 material
which I have available only in very rare cases.

My sources are mainly Full D1PAL 720x576 and NTSC720x480,
coming from camcorders (diverse SONY, Canon)
and capture boxes (Canopus ADVC-300).

SAR = SampleAspectRatio = Number of sampled pixels H / V
DAR = DisplayAspectRatio = Number of displayed pixels H / V
PAR = PixelAspectRatio = H / V SideLengthResizingRatio to be applied
to the sampled pixels before display
to have the source frame's aspect ratio displayed correctly.

Straight to the math:

PAR=DAR/SAR.

Broadcast D1 project will have 704 columns.
Some DVRs encode at Broadcast D1 resolution.

Full D1 projects, DV videocams and most capture boxes deliver 720 columns.

SAR for Full D1 (720 columns):

Full D1 NTSC: 720x480 -> SAR = 720/480 = 3/2 = SAR 1.5
Full D1 PAL: 720x576 -> SAR = 720/576 = 5/4 = SAR 1.25

Now the PAR for Full D1:

Full D1 NTSC 4:3
4/3 : 3/2 = 4:3 * 2:3 = (4*2)/(3*3) = 8/9 = 0.888.
(Not 10:11, this would yield 0.909 and this belongs to BC-D1)

Full D1 PAL 4:3
4/3 : 5/4 = 4:3 * 4:5 = (4*4)/(3*5) = 16/15 =1.066 .
(Not 12:11, this would yield 1.090 and this belongs to BC-D1)

Full D1 NTSC 16:9
16/9 : 3/2 = 16:9 * 2:3 = (16*2)/(9*3) = 32/27 = 1.185

Full D1 PAL 16:9
16/9 : 5/4 = 16:9 * 4:5 = (16*4)/(9*5) = 64/45 = 1.422

SAR for Broadcast D1 (704 columns):

BC D1 NTSC 704x480 -> SAR = 704/480 = 22/15 = SAR 1.466
BC D1 PAL 704x576 -> SAR = 704/576 = 11/9 = SAR 1.222

Now the PAR for Broadcast D1:

BC D1 NTSC 4:3
4/3 : 22/15 = 4:3 * 15:22 = (4*15)/(3*22) = 60/66 = 10/11 = 0.909

BC D1 PAL 4:3
4/3 : 11/9 = 4:3 * 9:11 = (4*9)/(3*11) = 36/33 = 12/11 = 1.090

BC D1 NTSC 16:9
16/9 : 22/15 = 16:9 * 15:22 = (16*15)/(9*22) = 240/198 = 40/33 = 1.212

BC D1 PAL 16:9
16/9 : 11/9 = 16:9 * 9:11 = (16*9)/(9*11) = 144/99 = 16/11 = 1.454

I would suggest to add the Full D1-PARs to the available settings
in Vegas and DVD-A to have a correct preview.

Please feel free to correct me if I'm wrong.

Comments

TheHappyFriar wrote on 12/6/2008, 8:11 AM

Vegas preview is correct. It previews the project settings. IE my default project is 720x480 29.970i & that's what it previews it. If you need a different resolution you can change that & save a template. Notice PAR is 100% seperate. You can make a 100x100 with a PAR for widescreen & make it wider then taller. You can make something wider then taller but adjust the PAR so it's square.

If the AR is wrong (thinks stretched/squished) on your computer monitor you have the "simulate device aspect ratio" unchecked. Right click on the preview window & make sure it's checked.

PAR has nothing to do with the project resolution. It's the actual ratio of the height/width of the pixels. Other apps display 786 because they don't actually display in the correct resolution & adjust the PAR, they add pixels so the pixel height/width ratio is the PAR vs adjusting the actual width of the simulated pixels.

here's a link showing Adobe has been wrong with the PAR for years while Vegas has been correct..

Coming from premiere years ago to Vegas I assume Vegas was wrong too until I found out otherwise. It's kind of like being told that there is no other life outside your house while you're a kid & then when you leave the house you see other people. :)

If you save a screenshot via the little disc icon in the preview window it will save it as a square pixel image so you can directly modify the image, load it up in a graphic app, edit, reimport & it will line up perfectly. If you copy to clipboard it will copy it as the resolution the preview is at so when you edit & reimport you need to change it's PAR to that of your video/project.

Emulgator wrote on 12/6/2008, 11:26 AM

I had the Simulate Device AR checked.
This provided me with the mentioned DAR of 1.364.

Unckecking provides me with the 5:4 SAR,
multiplied with the PAR of 1.000 of square pixels,
leading to a DAR of 1.25, which is expected,
can be used to see the encoded quality without resizing
but this can not be used as preview for design.

Neither of these versions deliver DAR 4:3 = 1.333.

The same footage imported in Edius 4.61 is shown in proper 4:3 AR there.

About the Adobe AR flaw I knew,
they also assumed Broadcast D1 PARs throughout their apps,
and rounded generously. Their fault.

And Microsoft did the same.
See:
http://www.mmbforums.com/ipb/index.php?showtopic=20930
especially the link to MS.

First I thought that Sony must have swapped digits 768->786.

If I look closer then it looks to me
as if the Broadcast D1-based PAR 4:3 calculation of
(my calculation and other's)
PAL 4:3
4/3 : 11/9 = 4:3 * 9:11 = (4*9)/(3*11) = 36/33 = 12/11 = 1.0909090...
or Sony's calculation (how do they get this, BTW ?): 1.0926

had been multiplied with the horizontal pixel count of 720 for a Full D1 project
(where this doesn't belong to) and voila:

My "incorrect BC-for FullD1" way:
1.0909 *720 = 785.4545 pixels, DAR would be then 1.3636
SONYs "incorrect BC-for-FullD1"way:
1.0926 * 720 = here come the 786.672 Sony pixels !
(Some say 786, some say 787...)

This is...well, enlightening, but does not provide us with a correct 4:3 picture.
The rendered output is well, though. 720 stay 720, SAR stays SAR.