MAMEWorld Forums - EmuChat - Re: quick help with aviwrite?

> I'm planning to record some game videos soon, but I found that aviwrite captures at
> the native res the game is set to.
>
> For some games this can look weird, for example Frogger (768x224) and Wonder Boy
> (512x224) to name just two. Why do those games display at those resolutions?

Because it was convenient for the hardware designers, and the resolution doesn't matter as long as the monitor can sync to it.

> Did the
> arcade hardware actually output at that, then the screen just stretched/squashed the
> picture to fit a 4:3 space?

Yes. Non-square pixels is the common case. The modern era of square pixels is the exception, not the historical norm.

> Q1. How can I force the output video in aviwrite to be the correct aspect ratio as
> seen on screen (I assume 4:3 for most screens) rather than the native resolution?

You don't. You do some back-of-the-envelope math assuming a 4:3 aspect ratio for horizontally-oriented games and a 3:4 aspect ratio for vertically-oriented games, and use that to determine what resolution to pass in for -snapsize.

> Q2. How can I prevent any kind of filtering when capturing, so the pixel sharpness is
> preserved?

-nosnapbilinear

> Q3. If I decided I wanted to capture at 1440p (for instance), how can I force that
> resolution in the exported video (e.g. 1920x1440 = 4:3), with no filtering?

See above, but your best bet is to render the video from MAME with square pixels and then do any re-scaling in an application of your choice.

For an example case: Take daytona, which outputs at 496x384.

This is a source aspect ratio of 1.2916-repeating which is shown on a standard display aspect ratio of 1.3333-repeating.

It's almost always best to target an integer multiple of the game resolution that is above your desired final resolution, so in this case that would be 1440/384 = 3.75, rounding up you get 4.

So in this case, I would run MAME with -aviwrite daytona.avi -snapsize 1984x1536 -nosnapbilinear and then chuck the resulting AVI into whatever application will give me the cleanest re-scale to 1920x1440.

It's almost always best to target an integer multiple of the resolution, since that will give you evenly-sized, evenly-scaled pixels in the source video, which makes it easier on your compositing software.