should use square pixels or not for 16:9?

[j.man]

I'm exporting a video (DV PAL 16:9 720x576, pixel aspect ratio 1,422) for youtube, and I need to know all the differences it makes whether I export it in a 1,422 pixel aspect ratio or in 1,0 square pixels, while keeping the original 16:9 frame aspect ratio. I'm looking for answers especially for these questions:
-which one requires less space? The 1,422?
-is quality lost if I export it to 1,0? (or does this depend on the output resolution?)

[guns1inger]

For youtube, loss of quality is a moot point - you will lose quality. Even the new 'high quality' clips on youtube aren't that great.

Also, youtube knows nothing about aspect ratio, so use square pixels or get a stretched image.

As you will be resizing down, quality loss from the resize/conversion to square pixels will be minimal. It is the conversion to youtube that will cause the real quality drop.

[j.man]

For youtube, loss of quality is a moot point - you will lose quality. Even the new 'high quality' clips on youtube aren't that great.

Also, youtube knows nothing about aspect ratio, so use square pixels or get a stretched image.

As you will be resizing down, quality loss from the resize/conversion to square pixels will be minimal. It is the conversion to youtube that will cause the real quality drop.

I thought it was kinda obvious, but I did mean with my question if more quality lost when I export to 1,0 than if I export to 1,422. Considering that the video is downsized to about a third of its original resolution, I am not so sure whether any quality is lost if one converts to square pixels instead of keeping the original pixel aspect ratio. (This question also interests me theoretically, even if one does need to use square pixels to avoid getting a stretched image.)

[jagabo]

If you resize your 720x576 16:9 source with square pixels for youtube the result will be a 320x180 image letterboxed in a 320x240 frame. If you maintain the 1.422 PAR you would end up with a 300x240 image pillarboxed in a 320x240 frame.

The latter will have more picture information and less border pixels. But, as was pointed out, youtube doesn't know anything about PAR it will just display your 1.422 PAR image as square pixel. So it will look distorted.

[j.man]

If you resize your 720x576 16:9 source with square pixels for youtube the result will be a 320x180 image letterboxed in a 320x240 frame. If you maintain the 1.422 PAR you would end up with a 300x240 image pillarboxed in a 320x240 frame.

Thanks. I don't see what I need the letterboxes for in this case, so I cropped them away. However, it seems youtube re-added the boxes when I uploaded the video. ( http://youtube.com/watch?v=zSbgSL1S5VY ) Even though compression and the VBR technology are used, I supposed boxes still increase file size.

[jagabo]

Noiseless black (or any color) borders consume almost no bitrate with these types of codecs. If the the bars contain noise (like from a VHS capture of a widescreen movie) they will require some bitrate.