On Wed, Feb 09, 2005 at 10:32:17PM +0000, John Gay wrote: > > On Wednesday 09 February 2005 17:54, Richard Ellis wrote: But you > > said above that you wanted max quality. Technically, that is > > "max" quality. Pov-ray created a pixel, the mpeg encoder > > faithfully reproduced that pixel. > > > > But I think you are trying to fix problem A by applying a > > solution for problem B. I surmise that what you are finding is > > that pov-ray is too perfect, in that non-horizontal/vertical > > lines show pixel stair-stepping. > > That's called aliasing, and POV-Ray does have the capability to > cope with this to some degree using Anti-Aliasing by super-sampling > the pixels, but I'm still seeing artifacts in the image. I was > hoping that I could use the mjpeg-tools to get rid of these.
But the scalers (yuvscaler or y4mscaler) are not intended to be anti-aliasing filters for sharp lines from a computer generated image. Both of them will try (to within the ability of their algorithms) to make the output scaled image as close to a faithfully exact copy of the input image as possible. Any anti-aliasing that may (and likely does) occur is a side effect of the scaling process and not a direct intentional result. > > In which case, instead of trying to utilize a possible side > > effect of a tool that was never intended to to do the job you are > > looking for, you should be investigating ways to convince pov-ray > > to output the images in the form you want. If you want smooth > > lines, try to find a way to have pov-ray do the edge smoothing > > for you. Or investigate other tools that will take a set of > > super sharp computer generated images and apply a smoothing to > > them. Because if you depend on a side effect of the scaler, you > > may find that if the scaler algorithms change a few months from > > now, that your side effect you depend upon disappears in the > > process. > > > I'll play around with AA a bit more. I'll see if ImageMagick or The > Gimp can fix these. I'd prefer something I can batch-process. I believe that many of the Gimp filters can be run batch mode somehow, but I don't know how to make that magic happen. As well, I seem to recollect that ImageMagick also has some support for batch mode runs. A true anti-aliasing filter and/or smoothing filter will give you a much better result than depending on scaler side effects. > > Maybe you should consider suggesting to the pov-ray development > > team the possibility of modifying pov-ray to generate non-square > > pixels. If they are already allowing the generation of interlaced > > frames, they are trying to be somewhat aware of "video" usages > > for pov-ray models. Well, in order to properly be "video" > > usable, non-square pixels are also a requirement. > > > But which of the many non-square sizes should they support? And why > should they spend time with that when video-based tools, like > mjpeg-tools already contain converters for this very purpose? Actually, I would think that once support was added for non-square, that supporting any ratio via a "aspect" input value would be a relatively small extension. I.e., 98% of the work would have to be done just to support a single non-square aspect ratio. It would likely only take 2% more to make it an adjustable parameter. I could be dead wrong, but this just seems like one of those situations where almost all the work comes in up front costs. > POV-Ray is primarily for creating computer images mainly displayed > on computers or printed. When it's used to generate animation > sequences, these need to be converted to what ever video format by > other tools, which already contain scaling tools. > > > You will get your best quality if pov-ray directly generates > > non-square pixels than by any post-processing to convert square > > pixels into non-square pixels. > > > Yes, but the POV-Ray team already have their hands full creating more > interesting rendering effects than adding support for several non-square > pixels that would only confuse everyone except us video making guys. You do make a valid point, and I'll concede that they very well may be by far more interested in more effects than supporting non-square pixel sizes. But you'd never know unless you asked, and the fact that they support interlaced frames (which technically are unnecessary for computer generated, computer displayed, and printed images) makes me think they might be slightly amenable to the idea. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
