Pixel aspect 1,0926 PAL DV - where this come from?

relaxvideo wrote on 9/19/2016, 1:14 PM

In 2000 i worked in a tv station, and all pictures on the timeline was in 768x576 square pixel or 720x576 nonsquare pixel format.
This is 4:3 aspect ratio, which PAL DV use.
Now i placed several 768x576 pixels photo on Vegas timeline, and curious that despite Vegas interpret this correctly as square pixels and the project properties was PAL DV, i saw black lines at left and right.

As i checked, project pixel aspect ratio is 1,0926. From where this value come from?

768/720 is 1,06666666...
768/704 is 1,09090909...

thanks

Comments

Marco. wrote on 9/19/2016, 2:09 PM

Correct square pixel accomodation of PAL DV is 787 x 576 pixel.

768 x 576 are adapted values from former analog times when lines of PAL signals had 52 μs length.
Many systems did incorrectly overtake these analog based values for PAL DV then, but length of lines of PAL DV signals are 53.3 μs.
Adobe Premiere/After Effects once used 768 x 576 for PAL DV and as a result a circle wasn't exactly displayed as circle. Meanwhile even those Premiere products uses a PAR of 1,0926. Vegas Pro always used that correct value and picture size.

So if you want to use photos/grafics inside a PAL DV project you'd better use 787 x 576 pixels for the photos/grafics.

Quitter wrote on 9/19/2016, 2:19 PM

1,0926 is PAL-DV (720x576) your project settings

relaxvideo wrote on 9/19/2016, 2:22 PM

ok, and what is the math for 1,0926?

Quitter wrote on 9/19/2016, 3:02 PM

PAL DV uses 625 lines per frame, of which 576 carry picture content
The pixel aspect ratio for 625-line video (PAL) is 59:54.

http://www.mir.com/DMG/aspect.html

relaxvideo wrote on 9/19/2016, 3:07 PM

ok, thanks, so complicated :)

OldSmoke wrote on 9/19/2016, 3:10 PM

Did you Google it?

Marco. wrote on 9/19/2016, 3:10 PM

720 * 1.0926 = 787 (rounded)

787 / 576 = 1.36 (rounded)

Aspect ratio of a PAL DV frame in which each of the pixels (720) of a line are used for video information (instead of leaving 9 pixels blank left and right) isn't exactly 1.33 (4:3) but 1.36.
Sometimes PAL DV calculations are made by 788 pixels/line, leaving 10 black pixels left/right and a frame ratio of 1.37 which is considered to be correct, too.
You'd get PAL DV with 1.33 picture aspect ratio only if there are 9/10 black pixels left/right.

Here is a link to a more precise explanation but it is German only.

Marco. wrote on 9/19/2016, 3:13 PM

PAL (analog) uses 625 lines. PAL DV (digital) does not.

relaxvideo wrote on 9/19/2016, 3:14 PM

great thanks, i just never saw this pixel aspect ratio value when i composed something in After Effects in 2000 :)

set wrote on 9/19/2016, 11:27 PM

Vegas Pro's square PAL DV resolution is different than other. I also get confused first time I move from Adobe Premiere. the 4:3 is 787x576, and 16:9 is 1049x576. I even create little macro on Photoshop to image size a little after make new.