The question is: is good to base on spectrum data to validate the quality of a LAME enc mp3?
...And in LAME 3.97, a 320kbps has an horrible frequency response (i still can see a net "cut" on 16KHz)!Some explanations are very appreciated! Thanks!
You don't listen with your eyes. It's as simple as that, hence spectograms are entirely worthless.If you really want to check the quality of an encoded audio track you have to conduct a blind ABX test of the MP3 vs. the source material and tell by yourself whether you're able to discern both files from each other. The goal of lossy encoding usually is to find a bitrate which is transparent to the human hearing, hence a quality that's indistinguishable from the source can safely be called a decent one, no matter what a spectrogram displays on the screen.I for my part usually ABX an encoded sample with different quality levels, starting from a low-bitrate one (like ~48 kbps with AAC and Vorbis) up to one that sounds transparent to me. Then I encode a few further samples using the bitrate which was transparent in conjunction with the previous sample and ABX these vs. the source as well. If at least one of these samples sounds flawed, the same procedure is repeated at the next higher quality step, until none of the samples can be distinguished from the source anymore. Having found this transparency threshold, I mass-encode using the next higher quality step as a safety margin for the possibly more problematic files which weren't tested before.And about the listening tests on these boards: People give their ratings depending on the perceived quality of the material they listened to before in a so-called ABC/HR test. The better the file sounds, the better the rating will be, e.g. if the tester can't tell a difference between the reference and the sample it's a 5 ("imperceptible").
That's all interesting, but is long to read (and translate), so i'll check out next days.
But my idea was that if the spectrum of an encoded sample is more similar to the original, it means that the encoded one has not so many data lost.
I don't have a great audio equipment, so for me the faster way to compare mp3s ...
... was a fast spectrum analisys (a 128k looks trimmed and dirty, a 320k much more clean!)...