Pixel Aspect Ratio

Coursedesign wrote on 12/22/2008, 3:20 PM
If you're not working on video for broadcast or higher end productions, you can probably skip this post and let your remaining neurons get back to holiday planning.

For the rest, there is this very thorough explanation of the world of PARs and how to properly deal with this total mess when editing:

http://www.lurkertech.com/lg/pixelaspect/

Comments

AtomicGreymon wrote on 12/22/2008, 4:00 PM
Pixel aspect ratio issues are a pain, yeah. When looking through a lot of the fan-made music videos on Youtube, you can see that a lot of them (made mostly with footage taken off DVDs, I guess) were uploaded without being changed to square pixel, so youtube just plays them with a 1.5:1 picture aspect ratio instead of the correct one. It's not like it'd be that hard to render at 640x480, 640x360, or 853x480.

I recently put together a DVD for an internet forum related to the film WALL•E (part of a Scrapbook thing they're putting together to send to Pixar as a way of saying thanks) and one of the entries I received had been created using footage taken off the widescreen DVD release, but the pixel aspect ratio of the actual video (which was sent to me in WMV) seemed to be NTSC DV fullscreen, so it was incredibly squished until I set Vegas to conform it to the proper widescreen setting.

I've been playing with footage taken off a Blu-Ray over the last few weeks, and it's been great working with square-pixels.
sibeliusfan wrote on 12/24/2008, 8:11 PM
Exactly so, AtomicGreymon—I see tons of incredibly squished fan-made and home-made videos on YouTube. It's puzzling to me how all these people can make these videos and yet not wonder why they look all funny and squished. Has it never occurred to them to ask for help, or inquire about what's going on? I don't get it.

Thanks Coursedesign for this link explaining pixel aspect ratio!
farss wrote on 12/25/2008, 2:20 AM
That's an interesting read, especially the part on mpeg-1/2 after my investigations regarding 16:9 DVDs.
It would seem that the sequence header does define the SAR:

"The MPEG-2 committee discarded the MPEG I pixel aspect table. But unfortunately it retained the notion that pixel aspect ratio depends on encoded image size. Pixel aspect of an MPEG-2 video bitstream sequence can be 1.0, or it can be specified in terms of a frame aspect ratio times a ratio of the image height and width in pixels. The frame aspect ratio can be a fixed value (4:3 or 16:9) or it can be encoded in the bitstream as any two integers. Unlike MPEG-1, it's possible to twist the MPEG-2 paramers around in order to make them say what they should originally have said: that the pixel aspect is 10/11 or 59/54. It's too bad that the committee didn't just offer these as constants."

Bob.