544x416 PAR?

[teknix1]

Hi,

I'm working on a resolution converter just to help me out on conversion projects and I'm a bit boggled about the strange 544x416 resolution. Could anybody please tell me what is the pixel aspect ratio for this resolution? Seems like Auto GK and Handbrake on Mac can produce these resolutions. Somehow this is related to the iPod or cell phones.

If you don't know what the PAR is, how would you go about converting a source to this resolution? What source would it be?

I've seen many posts about this resolution being 4:3 but it really isn't, it's 17:13.

Any help is appreciated.
Thanks
Nic

[paglamon]

If it is an avi file then, in all probability, it is using square pixels ,i.e PAR= 1:1.

I've seen many posts about this resolution being 4:3 but it really isn't, it's 17:13.

4:3 is not the resolution, it is DAR(display aspect ratio).
Suppose a file has a DAR of 4:3 and a resolution of 720 x 576,
then (720 x pixel width)/(576 x pixel height) = 4:3
so PAR(pixel width/pixel height) = (4x576)/(3x720)=16:15

[teknix1]

Sorry paglamon, that's what I meant (4:3)... the resolution has a DAR of 4:3.

Be carefull with the calculations you are advancing for PAR as they are not accurate. A source of 720x576 and 704x576 have the same PAR but not the same DAR.

Have you ever seen a file with this specific resolution? What I found on the net does not give me much to go as the aspect ratio is so close to 4:3 that I can't tell if the image when displayed as square pixels is right or not.

I suspect this resolution comes from some sort of crop of overscan from a higher definition source and then resized.

Thanks

[paglamon]

Be carefull with the calculations you are advancing for PAR as they are not accurate.

Then please point it out and rectify.

A source of 720x576 and 704x576 have the same PAR but not the same DAR.

Ofcourse not. And if they have the same DAR,the they will have different PARs.

Have you ever seen a file with this specific resolution?

Yes, and in other queer resolutions too. These are probably DVD rips(in avi) and some amount of cropping and resizing have been done. Since 544/416 is very nearly 4:3, the file is surely using square pixels and the actual resolution figures have been rounded off to the nearest values so that they are divisible by 16( as required by certain encoders).

[teknix1]

I will try to explain the correction to the best of my knowledge.
But first I must apologize for this statememt: "A source of 720x576 and 704x576 have the same PAR but not the same DAR.". I meant AR not DAR.
With that being said, I still think the calculations need corrections.

Using the following documentation (Section 3): http://lipas.uwasa.fi/~f76998/video/conversion/

All the DVD PAL resolutions (720x576, 704x576, 702x576) have a pixel aspect ratio of 128/117. 702x576 is the "active pixels" resolution. If you multiply that by 128/117 you get exactly 4:3, but you don't for the other resolutions.

This formula: PAR(pixel width/pixel height) = (4x576)/(3x720)=16:15, cannot be accurate as PAR never changes on TV. It's always 128/117 for PAL DVD resolutions. Now I don't have a PAL TV, but using my test NTSC DVD I created always shows the "active pixels" the same way for each resolutions. Everything outside the active matrix (if displayed) should be displayed using the same pixel ratio. I've seen many software DVD players doing this incorrectly and the image ends up either squished or expanded.

BTW, I managed to get a hold of a clip with 544x416 and noticed the overscan was included. So it had to play a part in ending up with this strange resolution.

[paglamon]

Thank you teknix for pointing out my slip. I did not consider the active pixels. But then, I did not mention that I was referring to DVD files. I was just giving an example of any video file(assuming that it had 720 active horizontal pixels). Again, thank you for elaborating on the issue.

[teknix1]

Active Pixels

Yes in that case, you're absolutely right!

A few more quick questions since I've got you here.

Which columns are not part of the active pixels for NTSC or PAL?
704 to 702 has 2 columns not being diaplsyed, are they on the left, right or one on each side.

Same question about overscan? 8 columns on each side?

How about VCD? This one doesn't support overscan I believe but how about that 1 column not part of the active pixels?

Thanks a lot for all the good info!
Nic

[paglamon]

You might find some answers here:

http://dvd-hq.info/FAQ.html

And according to this page,it seems that nowadays 720 active pixels are possible.