Why does MP3 transcoding lose so much quality? 2020-01-07 07:38:34 Hi all,I have a number of MP3 files that I want to trim, but can't, for one reason or another. Some are Lame VBR, which often makes trimming leading silence impossible (using mpTrim) without mangling the waveform. Others have noise too close to the audio. I decided to start with one of the latter, a 320k Lame encoding, and to test the transcoding process by converting it to WAV, converting the WAV to a new 320k Lame MP3, converting the new MP3 to WAV and then subtracting one WAV from the other. The two files are exactly the same size, the original encoding process theoretically has already discarded whatever frequencies it needed to, and the output is the same bitrate as the source. I expected the difference file to be inaudible, or nearly so, but it was nearly as loud as the original. I then used the same Lame version (3.93) that was used to encode the original file. That was significantly better, but the difference audio was only about 34 dB down (RMS) from the original -- still very audible. I'm looking for someone who knows enough about the technical details of MP3 encoding to explain why a naive transcoding seems to lose so much of the original sound and what, if anything, can be done to reduce the loss. Thanks in advance.