PDA

View Full Version : So this seems really weird to me. . .


slimeruky
2006-02-05, 10:06 AM
I am posting this to see what everyone's opinions on it are.

This is an old mp3 I had hanging around my computer, and I was just messing around looking at it and comparing it to lossless stuff I had. It just seems weird to me. There isn't the typical chopped off highs, and there doesn't seem to be much blocking either. The FA just boggles me.

Thanks for helping me out; I'm trying to improve at doing this myself. Thanks a lot you all.

Five
2006-02-05, 04:41 PM
can I get a copy of that mp3?

rapidshare.de or yousendit.com are the easiest ways.

perhaps it could be a wav file renamed to mp3?

slimeruky
2006-02-05, 10:18 PM
I know for a fact it's an mp3 because I remember my brother ripping it on to my computer forever and a day ago. I'd be happy to send it to you, but it's off an album, so I don't know how legal that is.

Five
2006-02-06, 04:06 PM
well if that's an mp3 it must be from some superduper lame encoder that is hidden from the general populace (like cars that run on water instead of gasoline).

slimeruky
2006-02-06, 08:40 PM
I'm pretty sure I have nothing special. It's mp3pro at 96kbps 22khz. Apparently it's a reasonably popular low-bitrate codec. Searching through my computer, the only program I have capable of writing mp3pro files is Musicmatch, so that must be it.
Info:
http://www.digit-life.com/articles/mp3pro/

range_hood
2006-02-12, 04:06 AM
Looks like a lowpass at around 9kHz and adding the above in some strange way. Mirroring is present, but in a (for me) unusual way.
Seems like the frequencies (4kHz to 9kHz) were copied to 9~14kHz - and above they were mirrored.
:hmm:

Five
2006-02-12, 03:36 PM
I tried encoding a track to mp3pro 96kbps 22khz and got some very interesting results... the frequency response goes right to the top unlike a normal mp3 (??!!). I could still find little block holes in the sa when I zoomed in, and some other artifacts... when I get the chance I'll play around with it some more and post up some screenshots.

slimeruky
2006-02-13, 04:35 PM
Very cool. I look forward to it. Thanks Five.

ssamadhi97
2006-02-15, 01:03 PM
Looks like a lowpass at around 9kHz and adding the above in some strange way. Mirroring is present, but in a (for me) unusual way.
Seems like the frequencies (4kHz to 9kHz) were copied to 9~14kHz - and above they were mirrored.
:hmm:
Yes, that's basically how mp3pro (and he-aac) work: they make a "normal" encode of the lower part of the spectrum where human hearing excels, spending almost their entire available bitrate there. Additionally, they generate a low-bitrate stream (maybe 2kbps) of auxiliary information that enables the decoder to artificially synthesize the treble range.

This encoding tool - usually referred to as SBR (Spectral Band Replication) - enables these formats to spend most of their bits on the critical parts of the spectrum, thereby improving the perceived quality of relatively low-bitrate encodes.

slimeruky
2006-02-15, 01:33 PM
I don't have a factual way to attribute this, since mp3pro is supposed to sound better, but those songs have the worst lossy slur of any I've come in contact with.