EAC... how perfect? How does it work?
Reply #26 – 2003-03-12 13:50:48
Let me rephrase: in digital audio, a 1 that should be a 0 can result in entirely different sound, or not? I can't see how errors could add/remove bass, depth etc. from a song... 1. If errors are detected but the original information is not restorable (by e.g. using error recovery information) interpolation will be done. Some (theoretical) example on the consequences: 1.1. Imagine, every 2nd sample is erroreous (1st correct, 2nd wrong, 3rd correct, 4th wrong ...) (and detected correctly). If best possible interpolation for this case is done, the result is the same as resampling a 22.05kHz signal to 44.1kHz. It's the same as applying a 11.025kHz lowpass. If the interpolation is not ideal for this case, e.g. linear: valueX=1/2(valueW+valueY), frequencies > 11kHz won't be cut away but "modified", causing aliassing and distortion. This is an extreme example, but basically it's the same if a few samples get interpolated. High frequency content is modified. 1.2. Imagine, you have a sharp transient, e.g. digital silence and suddenly a sample value of x000. If some samples before the 1st x000 sample are interpolated, the sharpness of the transient will be damaged, similar to pre-echo. 2.If errors are not detected e.g. because error detection information is not used, random errors can occur. This will result in a single sound, described as "click", "pop", "digital kiss" , depending on the error pattern. You can try these things yourself using a hexeditor and/or a wave editor.Corrections are welcome.