Topaz Labs used to sell a plugin pack for restoration tasks which
was the best of the best.
"Topaz Enhance" was able to deinterlace/denoise/upscale/fix compression/antialise etc mostly for SD video.
It is no longer available since they decided that in a DSLR area there is no need for a plugin like this.
Dave is kinda right. But the real powerful version of Instant HD was in the previous 1 and 1.1 version because it was powered by topazLabs.
However you should check it out, it might do the trick for you.
But I'd recommend you to see if you can find any previous demo of this amazing plugin.
"Line accent" filter is all you need. It was able to smooth any pixelated diagonal line.
Line Accent was part of "Topaz Enhance"
I requested a demo version of it almost 2 months before they decide to call-in it.
They sent me a 30days Trial activation Key and it was fully functional.
My copy it's for windows and I'm 95% positive there was a mac version also available.