What are encoding artifacts?

[Element]

Hi, I see references to being able to detect "encoding artifacts" sometimes in reviews. What are they and what do they sound like? Thanks

 

[gorman]

You get encoding artifacts when you compress music with a lossy encoder (MP3, AAC, Vorbis, etc.). An encoding artifact is a way for you to tell the compressed music from the original. There's many different kinds, actually. A difference in how a particular frequency is reproduced (or not reproduced at all), a glitch in the sound, an unwanted echo, and so on and so forth.

A glitch could be due to bugs in the encoder. Unfaithful reproduction of specific frequencies can depend on the quality of the encoder, its specific tunings and so on...

 

[DJGeorgeT]

Quote:

Originally Posted by Element Hi, I see references to being able to detect "encoding artifacts" sometimes in reviews. What are they and what do they sound like? Thanks

compression artifacts = byproducts in the final audio material, which were not present in the source material, that results from using a particular processing audio scheme. These byproducts either add extraneous sounds or completely alter the source material dynamics and sound.

examples of mp3 comression artifacts are: audible watery and metallic sounds (usually detectable in quiet passages) can affect the whole frequency spectrum.

Badly compressed audio can make the source material sound unnaturally harsh. The highs may sound broken and edgy.

There is more, I am sure.

 

[Spankypoo]

Artifacting is the addition of audio data which wasn't present in the source material.

But it's not the same as simple degradation - that's just something being taken from good to worse.

Try encoding something at an absurdly low bitrate (e.g., 64kbps) and listen to it - there'll be sounds which aren't present in the original material. The description of it being watery or metallic is spot on; it can also sound a bit like something rustling.

It's usually the byproduct of the algorithm of the encoder, and that can sometimes account for an encoder performing better at certain bitrates than others. In fact, occasionally higher bitrates have higher rates of artifacting if the encoder isn't optimized for those bitrates.

It's also worst on electronic music - pure waves tend to be very difficult to compress. (And it's most obvious when you have a simple wave which has been changed, rather than a certain portion of a complex sound being different.)