Aspect ratio

[Davor]

Don't know if i am at the right 'spot' but if someone has a better idea where to post this question, the idea is welcome

Take a look at this video file. When you play it in WMP it's AR is 1.86. When you click on the properties, it says the actual AR is 1.28 (704 x 552, square pixels probably), but the displayed one is 1.86. My question is: how do you make such file which seems to be anamorphic, but when played, it is reshaped to normal (unsqueezed) picture. ( thought it had something to do with the header, but with asf viewer i couldn't find anything.)

I can acquire the same displayed aspect ratio if i encode the scene with non-square pixels, but thats not the same as anamorphic (like this video file). As far as i know, anamorphic picture is encoded in square pixels and is decoded to nonsquare pixels (~16:11) so it seems natural (16/9).

Also, to mention, when i encode it in nonsquare pixels, in properties the aspect ration is 1.86. So displayed and actual AR's are the same as i see it.

As this is a WMV file i assume the maker used Windows media encoder to make it, but i don't know how, and i would like to know it

Also, i forgot the link where i found it

Davor

:

EDIT: can't upload the WMV file (1.7MB) Error: "The total filespace required to upload all the attached files is greater than your per post or global limit. Please reduce the number of attachments or the size of the attachments."

Global Space Left: 4.88mb

Edited September 24, 2005 by Davor

[svasutin]

As far as I know, the AR is not always the same as the PC pixel ratio. I believe, although theories vary, and I'm usually wrong, that the aspect ratio is determined by the device it is displayed on, and not the actual picture dimensions. This is why you see so much stuff on 704x480 and not 720x480 (NTSC). 704x480 with 4x3 AR yields a view of 720x480 viewing (integer stuff) for analog signals.

It is the whole, "TV adds ten lbs." thing. CRTs use lines, but some how it was figured out that the lines use 4x3 pixels when converted for PC use. The lcd/plasma tend to confuse people since they use square pixels likes computers.

Consider DVD, it has two formats, full and wide. full and wide are both 720(704)x480 (NTSC). Depending upon the input signal, the image either appears full screen or widescreen, but both are the same dimensions.

If have ever played a widescreen VHS tape on a normal TV, then you'd notice the people seem taller and everything looked squished; no letterbox that DVD players added. That is the effect of 16:9 on something that assumes 4:3.

This is common in WMP. WMP is not the best choice to play your file. If you have DVD software, or some other media player, see if you get the same results. You mentioned a viewer, the view should display your file correctly.

So, if you are coding for a TV/DVD, use 720x480, and set the AR to 16:9 (i believe you wanted widescreen). If you are coding for PC use only, then use overall 16x:9x dimensions with square pixels (x is a multiplying factor).

Hope this helps

BTW, you've got far too many icons on your desktop.

Edited October 19, 2005 by svasutin

[jdeboeck]

And for Belgium that would be 720x576 @ 25Hz because we use PAL.

As said, both widescreen and fullscreen DVD use the same resolution, but widescreen DVD are usually (but not always) anamorphic. This means the image in the 720x576 frame is stretched vertically. When displayed on a 16:9 television it is stretched horizontally, because of non-square pixels, and the image is normal once again. When displayed on a 4:3 television, one in four vertical lines is dropped. This will fit the entire frame on the television screen. Or the image is zoomed to fit, but then you lose the wide edges.

When you are encoding for display on a PC, always use square pixels. Even when your PC is attached to a television, it is better to use powerstrip to force a true widescreen resolution.

Edited October 19, 2005 by jdeboeck

[Davor]

Thank you for the replies but they are not what i asked...

This post is about a file which i can't upload, so you can't see it yourself. (i described it in my first post) It's about how you MAKE such file.

In other words, a wmv encoded stream, in an avi container, that is encoded in same resolution as the DVD anamorphic source, but that is displayed correctly. Which means that somewhere in the header of the avi there has to be a something that let the player know it has to strech the image.

The email notofication system isn't working well as i haven't got any mails on this subject, and the notification is enabled.

Greets

Davor

Edit: File Upload ERROR: The total filespace required to upload all the attached files is greater than your per post or global limit. Please reduce the number of attachments or the size of the attachments.

File is 1.68MB and Global Space Left: 4.8mb ... don't understand

Edited November 8, 2005 by Davor

[Scubar]

not sure about the video size thing but if i remember right u can only upload a maximum filesize of 1MB per post.