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Settings to accurately "un-squash" PAL DV to square pixels

Nov 30, 2012 3:34 AM

Tags: #pal #dv #squashed #resampling

Hi,

 

I just wondered if anybody knew the settings to "accuratly" un-squash DV PAL widescreen video?

 

I've "done the math" and the results just don't cut it.

 

For example:

 

The original DV is reported to be 720x576.  So using "square pixels" and a 16:9 aspect ratio, by rights the output size should be 576*(16/9) = 1024.  Settings:

 

dv settings1.PNG

 

However there are two issues here.  Firstly I get two thin black bands top and bottom of the image - so this is crazy since if the input video is 576 pixels and the output is also 576 pixels, why has Premiere Pro resampled in the vertical direction?

 

I've noticed that by setting the width to 1054, I can make the black bands dissapear but this 3% difference in expected aspect ratio is very disturbing.

 

Even then the resampling quality is poor.  My original video has a title on the screen (white on black - static and constant throught the video) here's a screen grab:

 

logo_original.PNG

 

The 1024 pixel wide version looks like this:

 

logo_1024.PNG

Significantly worse I think you'll agree. Now some of this could be related to the H.264 compression but I suspect that most of it is due to unnescessary resampling artifacts in the vertical direction.

 

Here's the 1054 width version (still 576 high):

logo_1054.PNG

And for fun here's a 1052:

logo_1052.PNG

Notice in all these examples how the horizontal "resampling" is being affected (especially bad in the 1054 version) and again note that I'm not changing the height at all!!!

 

So my question is:  Why does changing the width of the target video affect the resampling in the height when I've specifically selected the exact height and switched off the "preserve aspect ratio lock"?  I think this is a bug.  This would not be a problem in Photoshop...

 

Alternativly, please let me know where I'm going wrong and what settings I should use to preserve vertical resolution precicely, whilst stretching the width by a factor of 16/9.

 

Thanks in advance for your help!

 
Replies
  • Currently Being Moderated
    Nov 30, 2012 4:23 AM   in reply to will.reeves

    Did you not get this error message when changing the image size to 1024 in the export panel?

     

    error.jpg

     

    This shows that its not happy and could well be the source of your problem. However if you leave the image size as 720 x 576 and use

     

    Format = H264

    Preset = Pal DV widescreen

     

    the problem does not occur and vlc player displays a widescreen image without the blank lines.

     
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  • Currently Being Moderated
    Nov 30, 2012 5:19 AM   in reply to will.reeves

    If level and profile are set high enough you dont get an error message.

    As Adobe changed the PAR try 1050x576, works for me.

     
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