aspect ratio

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hdmickey
Posts: 16
Joined: 11 Nov 2011 02:08
Location: US

aspect ratio

Postby hdmickey » 12 Apr 2012 04:16

Hi,

I'm having trouble with aspect ratios in HD video.
The problem is that, the original footage is 1920X1080 and or 1440X1080
The end result of this footage will be burned to a standard DVD to which only format can be 720X480 mpeg2 from my understanding.

When I render the 1920X1080 files, the only thing I can do is export it in 720X480 mpeg2, when I open the rendered video with Windows Media Player, it seems to keep the aspect ratio in place, but when I reload the video in a different editing program the aspect ratio is wrong, it looks like it zooms in and stretches the image too.

I've noticed something with that 2nd editing program, when I import the raw 1920X1080 file, it is totally fine, but when I import the rendered file from the first program (HD video that has been rendered at 720X480), even though windows media player displays it properly, the editor will cause distortion no matter the settings of the project.

I could skip the the whole problem by using the 2nd editor with the raw HD footage, but since this is to burn to regular DVD, eventually it will change to 720X480 and I'm worried the aspect ratio will be wrong on the finished DVD, is there something I need to change to get it to show properly? This problem is only with widescreen HD video (1920X1080, 1440X1080), with widescreen in DV quality, it seems to be fine.

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Stephan
Site Admin
Posts: 592
Joined: 20 Mar 2010 18:51
Location: Paris, France

Re: aspect ratio

Postby Stephan » 12 Apr 2012 15:06

Hi,

As you figured, it's not just the resolution that counts - each video file has a Pixel Aspect Ratio flag stored somewhere in the file that will tell either the video player, or your editing software, how to interpret the video.

For example, here are various combinations;
- HDV is 1440x1080 with 4:3 pixel aspect ratio (rectangular pixels),
- "Full HD" is 1920x1080 with 1:1 PAR (square pixels),
- Widescreen NTSC Standard Definition is encoded as 720x480 with 40:33 PAR (rectangular pixels),
- Widescreen PAL SD is encoded as 720x576 with 16:11 PAR (rectangular pixels).

So:
1. When you export a video file out of your editor, you need to make sure you're exporting it with the correct PAR specification - there's ordinarily a setting for that (use the right export template), it's usually a list box with commonly-used PARs.
2. When you import a video file, or even a still image, you also need to make sure that your software is taking the right assumption about the PAR - for instance I use Final Cut Pro and Motion (for animations), and for each "asset" (video file or image) I can check that setting and fix it if the software assumes it's square pixels when it's not.
3. When you prepare your DVD for writing ("DVD authoring"), make sure your authoring software is correctly assuming the input file is widescreen PAR, and make sure you're specifying that it is a widescreen DVD you're making.

So in summary:
- Always stick to the target / native pixel aspect ratios when importing / exporting, never - ever - try to resize to square pixels.
- Make sure that every software you're using in your workflow is aware what's the correct PAR for each file.

Once that's done, I figured that video players (Windows Media Player, or VLC, or QuickTime player) are ordinarily very well capable of detecting the right PAR and displaying it right. If it doesn't for you, you probably lost the PAR setting somewhere in your workflow.

Hope this helps,

Stephan

References:
http://en.wikipedia.org/wiki/Pixel_aspect_ratio
http://en.wikipedia.org/wiki/Standard-d ... pect_ratio

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GK2047-10B
Posts: 8
Joined: 23 Jan 2012 14:19
Location: The Netherlands

Re: aspect ratio

Postby GK2047-10B » 06 May 2012 23:02

Hi,

Could it be that when you reload to files into your project that you have to reset your project settings first prior to reloading? Maybe your project setting are in DV en that turns the imports into DV formats...~

Ben


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