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Dealing with Aspect Ratios
The first rule of resizing:
Before we talk about the various options there is one important fact you need to consider - you must never resize interlaced footage in order to change the vertical size. You can stretch the footage horizontally all you want but if you change the height of the frame it will totally mess up the interlacing. Many of the settings on this page are best used on progressive footage only, and if you have followed this guide then you should not have interlaced footage at this point anyway.
Editing with DVD PAR or square pixels?
As you should know by now, DVDs don't have square pixels, and so we will need to correct this. Because aspect ratios can be very complicated things, I prefer to make things as easy as possible. This means resizing your footage so that it has square pixels. When you are working with square pixels, what you see is what you get. There are fewer oportunities to screw up or get confused. For this reason, I would recommend you always resize your footage before editing. For completeness though, I will also tell you what to do in case you want to edit with the footage at its original size.
Getting Ready for WMM?
Working out frame sizes yourself:The brave of you out there, instead of simply reading the values on this page, will want to find out correct aspect ratios themselves. To help you, I recommend you read over this page, which details how to use a resize calculator and how to find correct cropping values.
1) Keep DVD Resolution and PAR
You can edit at full dvd resolution if you like (720x480 for NTSC and 720x576 for PAL) but any graphics you make for your video (like text etc.) will be at a different Pixel Aspect Ratio. To compensate do this:
NTSC Graphics: Make images at 720x528 and resize to 720x480 to have DVD PAR.2) Resize to Square Pixel Aspect Ratio (Recommended)
If you don't want to have to worry about how your graphics and other elements will look, you can always convert your footage to square pixels before editing. You will note that this method involves a little cropping - this is perfectly natural and it is required to create the correct aspect ratio. I could explain why you need to do this... but it would take me all day, so just trust me.
NTSC Footage: Add this to the end of your avisynth scripts:You should then set up a profile in your editing package to edit at square PAR with that resolution.
1) Keep DVD Resolution and PAR
You can edit at full dvd resolution if you like (720x480 for NTSC and 720x576 for PAL) but the video will look very stretched vertically in your editing application. Also, any graphics, text or other footage you add to this will be a different PAR so you need to fix that before adding them to your video:
NTSC Graphics: Make images at 848x480 and resize to 720x480 to have DVD PAR.2) Resize to Square Pixel Aspect Ratio (Recommended)
If you want to edit with What You See Is What You Get then you can always convert your footage to square pixels before editing.
NTSC Footage: Add Spline36Resize(848,480) to the end of your avisynth scripts.You will note that these are very wide resolutions but this is in order to keep the vertical resolution in order to avoid losing any quality.
This is a much more problematic arrangement as one of the sources is
going to have to lose some footage with cropping and if you have
anamorphic footage you may need to do some resizing too.
First off, you have to decide whether you will make your video in 4:3 (fullscreen) or 16:9 (widescreen). Most people usually go with widescreen because it looks more cinematic, but you lose less important parts of the footage if you go with full screen.
If you are making everything fullscreen, this is pretty simple. Assuming you are working with NTSC footage and square pixels, you simply have to crop your 848x480 widescreen footage down to 640x480. If you crop 104 pixels off the left side, and 104 off the right side, you are all set.
If you want to make everything widescreen, its a bit more complex. First you need to upscale your 4:3 footage so that it matches the width of your widescreen footage while still retaining the proper aspect ratio, and then you need to crop from the top and bottom until it matches the vertical resolution. Assuming NTSC footage with square pixels, this means I would resize my 640x480 footage up to 848x636 (because its a 4:3 resolution with the same width as my widescreen footage), and then I crop it down to 848x480 by cropping 78 pixels from both the top and bottom.
Hopefully you can work out the correct values for your own footage.
1) Only try converting a source with progressive frames. Interlaced sources are tricky to convert. If you really need to convert an interlaced source, read about the separatefields() and weave() commands in the avisynth manual and then ask about it on the forums