PAL image size

mitchell65 · Post by **mitchell65** » Tue Dec 15, 2009 8:00 pm

erdna wrote: My experience is that it doesn't make any difference in resolution when e.g. zooming is applied.

It does on my HD TV

erdna · Post by **erdna** » Wed Dec 16, 2009 12:13 am

I retested on a fullHD TV, and indeed there is a difference. Edges are somewhat sharper, but there is a lot of aliasing, which make e.g. that a text on a banner in the image becomes almost unreadable when VS has to resize the large image. Apparently the oversized image is just being resampled without any Nyquist refiltering. I compaired a 3648x2736 image (straight on the timeline) with its resized (768x560) version on the same timeline. Made a 720x560 MPEG2 video file and played the file on my fullHD monitor through my PowerDVD8 SW player.

Ken Veal · Post by **Ken Veal** » Wed Dec 16, 2009 1:05 am

jpeg ,RGB True colour, 24bit,Width 3071 Height 1838px,Res 28 px/cm,
size 16,537kb

Trevor Andrew · Post by **Trevor Andrew** » Wed Dec 16, 2009 10:18 am

Hi Erdna

erdna wrote: I compaired a 3648x2736 image (straight on the timeline) with its resized (768x560) version on the same timeline. .

With these images in the timeline, use pan and zoom on each, compare the difference in the timeline.

erdna · Post by **erdna** » Wed Dec 16, 2009 11:55 am

With pan and zoom it's even worse. an extra strong flicker on the characters becomes visible. Is there a way to post my .jpeg files (the original pic and the presized) so that other people can do a test?

erdna · Post by **erdna** » Wed Dec 16, 2009 12:07 pm

I uploaded the 2 files in http://users.telenet.be/bettydemey/

erdna · Post by **erdna** » Wed Dec 16, 2009 12:22 pm

I now added screenshots of the result ( not yet pan/zoomed) in an mpeg2 file played back with PDVD8.

erdna · Post by **erdna** » Wed Dec 16, 2009 3:17 pm

Finally I found out that if you don't apply pan/scan on an oversized image it is being rendered without the right filtering, thereby causing aliasing. If pan/scan is being applied and the file rendered, the end result is indeed significantly better. (resolution). I now also uploaded the "problem" .mpg file where the pre-sized, and the oversized image clips were rendered without pan/scan applied. My conclusion is thus, to never use oversized image clips if there is no P/S involved.

Trevor Andrew · Post by **Trevor Andrew** » Tue Dec 22, 2009 12:43 pm

Hi erdna

Sorry for the delay in replying and thanks for the info and sample clips.
Interesting result.
In the past I have always used sizes to match the video frame, only recently increasing (double size) for my slide shows.
I don¡¦t use Pan & Zoom that much so will be taking a good look at the next slide show.

By the way I noticed you used interlaced video, have you try Frame Based for your slide shows.
I realise with video included we would use interlaced. Just a thought.

Alludo USER to USER Web Board

PAL image size

Image Size