No, I am talking of one. One old mp3 with artifacts we could by now know how to identify algorithimically and filter away in a way that more often than not results in an improvement.
I assumed you mean A/Bing multiple samples to figure out what was an artifact. If not, how exactly do you propose to figure out what is an artifact? And what would you do about it?
It might have been deliberately introduced--you could only tell for sure by comparing--but he'd still like it gone. Would that be possible?
How do you "remove" something without knowing what it sounds like? Aside from muting the audio that is
Processing filters to remove encoding artifacts such as blocking, banding, ringing are rather common in video[...]to get better perceived quality
Just a heads-up on this topic, there is a shareware Photoshop plugin that cleans JPEG artifacts and does an amazing job at that (it's called Topaz DeJpeg) and has some before/after images at the bottom of their website: