mp3 to wav to mp3 to wav same? Options

[gts]

If a file is encoded to mp3, then coverted back to a wav, and then that wav is convered back to mp3, will the both mp3s be the same?

[Doctor]

aggies: no.

Lossy sound encoding is not like you described. It's more like analysing the frequency content of the file in small chunks, deciding which frequencies to dump or round and compressing the frequency information. The decoding is then synthesizing the frequencies back into waveforms while making sure that small chunks flow smoothly into each other.

Frequency information is more complex than the waveform, so you would know enough to reconstruct it.

If you try to analyze the file again, you will get the frequencies that were in the first mp3 plus noise coming from rounding and smoothing the chunks together. The encoder will not necessarily be able to tell that the noise is to be discarded, in fact, the noise may modify your original frequencies in unpredictable ways. So the encoder may decide to dump or round something else.

There was another thread recently, where we could agree that in theory one could write a codec that would be reencode without loss. However, the codec would be very inefficient.