Re: [GnomeMeeting-list] Would vertical bars in image affect transmission?

[Damien Sandras <dsandras seconix com>]

On Sat, 01 Dec 2001 13:29:09 -0500
nathanstenzel netscape net (Nathan Stenzel) wrote:

> I just noticed there are tiny vertical stripes in the images that come from my webcam.
> Basically, every other column of pixels is darker than they should be.
> By some experiments with my webcam, camserv, and a fitler I wrote for it, I found out that the stripes also make it harder to compress the image.
> I wrote the filter to basically blur the image horizontally thus removing most of the affect of the striped appearance.
> Those stripes might not normally be noticable, so it is hard to tell who else might have them in their webcam's images.
> 
> I was wondering if it made sense that sense thsoe stripes make it harder to jpeg encode the images that they also made it harder to compress the images in whatever format that gnomemeeting uses.
> What do you think?

I have absolutely no idea about that. But it can certainly lead to errors.

> I would like to suggest the idea of an optional prefilter on the images to help smooth out images before compression.
> I don't have much time, so I don't think I could really write the code myself.
> I would suggest that the prefilter apply a 3x3 convolution matrix though.
> That way, the person could modify the matrix for blurring or sharpness or contrast or embossing or whatever.
> The main advantages would probably come from blurring (for low bandwidth people) or sharpness enhancements.
> Does this seem like a feasible and useful idea?

It is feasible, but I wonder if it would not eat too much CPU time for a real-time audio/video communication.
0.12 applies a slight interpolation on received images before displaying them. You can get a very good image 
quality with a good interpolation, but in that case, the CPU suffers a lot.


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