No amount of oversampling or post-processing can truly mask a MP3 files flaws (or indeed any lossy file format). Although a 20:4 bit ratio should yield a good enough playback. In comparison to say, 24/48Khz FLAC format the difference is very discrete however as this is not a common format used by major music vendors it will take a while before they realise that "us audiophiles" aren't that impressed. MP3 is over ten years old now although the LAME encoder does make some improvements over the original algorithms.
 
Try saying that drunk.

slightly ot, interesting site here http://theghostinthemp3.com/

interpolated
No amount of oversampling or post-processing can truly mask a MP3 files flaws (or indeed any lossy file format).

But luckily our ears very often can.
 
Of course you have to understand just how profoundly lossy our ears are and how much data they throw away before it even gets to the auditory nerves and thus the brain. 
 
If a lossy format manages to only throw away the exact same stuff that the ears do, it is completely transparent. The trick is in coming up with an algorithm that automatically does that for as many very different signals as possible, while making good compromises in the situations where stuff can't be masked completely. And of course it becomes more and more difficult at higher and higher compression ratios.
 
One also must not be too lazy or overconfident to do some careful ABX or double blind testing to separate the real artifacts that do remain audible from the many, many imaginary ones. That's really the only effective way to evaluate lossy compression if one cares about reality.

Inverting the phase of the mp3 against the original before the render took place would display any sonic differences as a waveform. Just a small signature. You wiuld need a more forensic approach to notice anything else like spectral display or such like.

interpolated
Inverting the phase of the mp3 against the original before the render took place would display any sonic differences as a waveform. Just a small signature. You wiuld need a more forensic approach to notice anything else like spectral display or such like.

Not quite. It would reveal data differences, not sonic differences. "Sonic" implies audibility.
 
There's a plugin that does MP3 conversion on the fly so you can hear what your mix will sound like when encoded. It also has a feature that lets you hear only what's been removed. It freaks users out! 
But what they forget is that ideally the conversion is merely removing what your ears and brain would have removed anyway.

Pernickity bitflippity!
 
A placebo effect, you can't miss what you never heard.
 
 

Yes. The problem with using a difference signal is that the evaluation needs to take the psychoacoustic masking into consideration or it's completely useless, because the psychoacoustics is exactly what the stuff in the difference signal is based on. And in creating the difference signal you just took away all the stuff that's doing the masking.

So what you're saying it's money for old rope then? 

I wouldn't use that phrase, but that's mainly because it's a British aphorism and I speak 'Markan.
 
Perceptual coding can seem like magic, and at some level it kinda is, because few understand it beyond the general conceptual level. Look it up on wikipedia, but jump down to the references at the bottom and read some of the source literature. If you can make it through the whole thing without falling asleep, you have a greater attention span than I do.