Is this what you're talking about?

If so it's called mosquito noise and it's a compression artifact. You can filter all you want, but it's coming from your encoder not your source.

Try lowering your quantizer characteristic (or your encoder's equivalent).

Mosquito noise, a.k.a. Gibbs effect
Mosquito noise is most apparent around artificial or CG (Computer Generated) objects or scrolling credits (lettering) on a plain coloured background. It appears as some haziness and/or shimmering around high-frequency content (sharp transitions between foreground entities and the background or hard edges) and can sometimes be mistaken for ringing Unfortunately, this peppered effect is also visible around more natural shapes like a human body. The VIRIS project (a Video Reference Impairment System) defines mosquito noise as follows: "Form of edge busyness distortion sometimes associated with movement, characterized by moving artifacts and/or blotchy noise patterns superimposed over the objects (resembling mosquito flying around a person's head and shoulders)."

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Mosquito noise

It occurs when reconstructing the image and approximating discarded data by inversing the transform model (iDCT).

"Mosquitoes" can also be found in other areas of an image. For instance, the presence of a very distinct texture or film grain at compression will also introduce mosquito noise. The result will be somewhat similar to random noise; the mosquitoes will seem to blend with the texture or the film grain and can look like original features of the picture.

(From http://www.videsignline.com/howto/180207350)