PDA

View Full Version : D1 PAL Widescreen



oab
04-21-2009, 06:19 PM
Still using 8.5
Trying to render out PAL Widescreen image sequence and although the camera is set to D1 (PAL Widescreen) with a pixal aspect of 1.422, the frames are being exported as square pixals therefore the image appears 4x3. Has anyone else come across lightwave ignoring the pixal aspect with this setting and perhaps have a fix.

Thanks

RebelHill
04-21-2009, 07:16 PM
no... if its set to be widescreen, with a nonsquare pixel aspect, then the resulting image will be 4:3... if it were square pixels, you'd be getting a 16:9 image.

oab
04-21-2009, 07:36 PM
If this were the case why when setting the PAL D1 Widescreen does lightwave make the pixal aspect 1.4222

I just tried again by changing the PA to 1.0 but it makes it a custom setting and gets squashed up even further.

Murphy
04-21-2009, 11:12 PM
I've had similar problems before. Seems the camera options will override the lightwave output options even if you have it set to D1 PAL in the render globals.

Open up the camera properties and make sure it is set to
Width: 720
Height: 576
Aspect: 1.42

Also you need to set up the field rendering here too. I prefer to work in progressive myself as i think it looks prettier (more like film), but if you are composting into live video footage it might need to be interlaced to match.

Out of interest is there any reason you're doing the aspect in lightwave and not third party editing/compositing package like aftereffects? From personal experience I find it a much better work flow to work entirely in square pixels right through the post processing up until the final product has to be mastered out.

Higher quality images for post production and effects purposes, plus it causes allot less headaches with other people working on the project that don't understand nonsquare pixels and aspect ratios (you be surprised how many professionals in the industry don't get it...)

oab
04-22-2009, 01:23 AM
Thanks Murphy
I've got the camera settings set and Render Globals turned off so should use the camera settings. No compositing as it's all animation so thought I should be able to render directly from lightwave. Chose 720x576 widescreen as it's exactly the same frame aspect as 1920x1080 HD so can render out good quality now and render out full HD later without changing anything except the resolution. As a test I used custom setting for HDV PAL 1440x1080 pixal aspect aspect 1.333 and the same thing happens that the rendered image defaults to a PA of 1.0, yet the full HD default setting works fine ? Can always use a work around but just thought Lightwave could do something as basic as that, guess not ?
I'm not surprised regarding your mention of others not understanding ratios etc, did some animations once for someone editing on Final cut and he didn't know what a field was ?
Thanks for the info

RebelHill
04-22-2009, 03:13 AM
If this were the case why when setting the PAL D1 Widescreen does lightwave make the pixal aspect 1.4222

Because 1.42 is the standard for pal d1 widescreen... its a non square pixel standard...

and 720X576 is NOT the same aspect as 1920X1080... Do the math...

(1920/16)X9=1080... (720/16)X9=405

720X576 only comes out as the same aspect because it uses NON SQUARE pixels... 405X1.4222=575.991 (close enough 576)...

What LW is doing is normal, and correct... Either render a 16:9 frame with square pixels, then let ur video apps take care of the pixel aspect later... or just roll with it, and trust LW.

Murphy
04-22-2009, 04:10 AM
Ah, ok. RebelHill is actually quite right. Unfortunately there is really no shorthand way of explaining what is going on so bear with me.

Depending on the settings and the equipment D1 PAL uses a variety of different pixel aspects. To start lets look at Square pixels as its the easiest to wrap your head around.

Computer screens (typically) have square pixels. If you open up say a new photoshop document that is 512x512 pixels, it will appear on screen as a square. This is because the computer screen has a pixel aspect ratio of 1:1
What this means is that a 720x576 PAL image is going to appear as a 5:4 image. This image will typically appear squished as its meant to be shown as a 4:3 image with a 1.06PA or a 16:9 image with a 1.42PA... Comprendes?

Now, on a CRT glass monitor with a non square pixel aspect (Or more likely these days an LCD with anamorphic pixel correction). In this instance the rectangular pixels will have an aspect of 1.42:1. The rectangular pixels will stretch the 720x576 PAL image out to its proper 16:9 size. This is anamorphic PAL.

Why may you ask? The reason is basically twofold.
A) With composite analogue video systems, stretching the 720 image on the screen to various sizes at the end of the process, is far easier technologically than developing an entirely new video system.
B) It means that you can broadcast a windscreen signal with no additional bandwidth costs. Similar to how interlacing allows you to double the frame rate and 4:2:2 chroma subsampling allows you to drop the amount of colour data per pixel with negligible loss of image quality.
As a side note 35mm often uses anamorphic lenses so you can use standard 35mm film appear at an aspect of 2.39:1, but thats niether here nor there...

What does this mean to you?

So if you want your PAL widescreen stuff to appear on the computer screen at the correct aspect you need to render it out as 1024x576 with a Pixel aspect of 1:1
720x1.42222... = 1024
720x142.22% = 1024
576x16/9 = 1024
but keep in mind this isn't true PAL)

1920x1080 uses a square pixel aspect. That means it has a pixel aspect ratio of 1:1 so that should appear to be just dandy.

If you want your PAL sized test render images to appear on the COMPUTER SCREEN at the right aspect use a pixel aspect of 1:1 (or 1.0 or whatever) with an image size of 1024x576

Ok, so thats the best i can explain it... hope it made sense

Epilogue:
As suggested earlier, anamorphic pixels and different aspects are a headfuck and for your sanity and the sanity of those around you, work in square pixels up until the end product has to be mastered out to a PAL video system like Sony DigiBeta.

blindsided
04-22-2009, 05:06 AM
From my experience, d1 widescreen in LW renders out 16/9 FULL HEIGHT ANAMORPHIC, soo the image file or QUICKTIME output would be 720x576, but stretched vertically, if u open in Quicktime player, you can get the player to compensate for the pixel aspect ratio and play in the a widescreen viewer.

hope this helps

Murphy
04-22-2009, 05:19 AM
Because 1.42 is the standard for pal d1 widescreen... its a non square pixel standard...

and 720X576 is NOT the same aspect as 1920X1080... Do the math...

(1920/16)X9=1080... (720/16)X9=405

720X576 only comes out as the same aspect because it uses NON SQUARE pixels... 405X1.4222=575.991 (close enough 576)...

What LW is doing is normal, and correct... Either render a 16:9 frame with square pixels, then let ur video apps take care of the pixel aspect later... or just roll with it, and trust LW.

Also i feel i should point out that this is perhaps not the best example as anamorphic pixel aspects are almost never applied vertically as it can potentially cause horrible HORRIBLE problems with the interlacing feilds (as if the bastards don't cause enough problems as it is... :P).

In fact the only time i've EVER seen PAL footage default to 404 pixels high is when quicktime tries to display m2v Mpeg2 that have been run out of compressor or DVD StudioPro... And the jury is still out on this one but the general consensus seems to be that its a display error within quicktimes Mpeg2 codec and is in fact true 720x576 despite what quicktime says.

Murphy
04-22-2009, 05:40 AM
From my experience, d1 widescreen in LW renders out 16/9 FULL HEIGHT ANAMORPHIC, soo the image file or QUICKTIME output would be 720x576, but stretched vertically, if u open in Quicktime player, you can get the player to compensate for the pixel aspect ratio and play in the a widescreen viewer.

hope this helps

Previous post also applies to what blindsided said too. The pixels on your PAL video outputs from lightwave arn't stretched vertically, they are squashed horizontally. If it where vertical it could potentially cause the interlacing fields to blur into each other when its upsampled/downsampled.

He does make a good point that you can open the Movie Properties on your D1 PAL clip in quicktime (assuming thats what you use) and have it display as 1024x576 16:9 on screen...
Though this can cause problems later on when the editor who isn't playing attention to what he/shes doing drops it onto a 720x576 anamorphic timeline in finalcut or whatever and it ends up being squashed and letter boxed inside of an already 16:9 frame. If you're going to do this you may as well just run it out as square pixels to begin with.

blindsided
04-22-2009, 07:53 AM
just to confirm, i didnt mean to imply the pixels are stretched vertically, just that the image appears stretched vertically due to the aspect ratio of the pixels.
Also the Quicktime player does not scale the image to 1024x576, you actually choose it in the presentation, and the player compensates for the pixel aspect ratio, rather than scaling it to a user defined value which does not give a true representation of the image.
Also this means that in FCP you would place the clip in a 720x576 anamorphic timeline, just be sure to tick the anamorphic setting in the bin prior to placing the clip in the timeline.

Murphy
04-22-2009, 08:28 AM
just to confirm, i didnt mean to imply the pixels are stretched vertically, just that the image appears stretched vertically due to the aspect ratio of the pixels.
Also the Quicktime player does not scale the image to 1024x576, you actually choose it in the presentation, and the player compensates for the pixel aspect ratio, rather than scaling it to a user defined value which does not give a true representation of the image.
Also this means that in FCP you would place the clip in a 720x576 anamorphic timeline, just be sure to tick the anamorphic setting in the bin prior to placing the clip in the timeline.

Huh, thats rather useful setting. i'll have to keep that one in mind for future reference.

danielkaiser
04-22-2009, 12:57 PM
If your importing into After Effects, Premiere or similar App. you have to tell it to interpret the footage in order to have the proper aspect.

oab
04-22-2009, 01:55 PM
Thanks for all the help. It does appear to be square pictures on LCD etc as have done a couple of test renders, imported into FCP and is ok on widescreen sequence. I just like pressing F9 to do test render frames as I go along was where it wasn't showing properly, so I'll change the camera settings while working so I can see the frames correctly, then change settings for final render.
Thanks again