calculating noise in video or image

[manit]

When our cable telivision signal is weak then we see grains on screen otherwise the picture is sharp . Can we calculate that ?
Actually I am trying to differentiate between good & bad video (obtained in desktop using tv tuner card) using imagemagick.

[fmw42]

calculate what? what image format?

[manit]

I can extract jpg frames from video obtained.
Is there a difference in brightness,contrast (or any pother parameter) when image blurs so that I can use to quantify the jpg as sharp or blurred.

[fmw42]

No technique that I know about of the top of my head. Perhaps someone else might know a way.

[anthony]

There are many forms of noise, and you can get some idea of how much a specific type of noise there is, but only in the general case.

For example 'snow' or 'salt and pepper pixel noise' can be figured out by looking for isolated pixels.


However in general it is difficult to get a qualitative indication of how much noise their is. I mean is that 'fuzzy square' an artifact of JPEG compression (in low quality MPEG video), or is it really part of the scene?