Rockbox mail archive
Subject: Re: low-fi mp3s
From: Neon John (johngd_at_bellsouth.net)
I've noticed this of late too, when playing 32kb, 8khz sampled audio books.
The high frequency tone (probably 8-10khz) is of fairly low level, doesn't
appear to change with volume or other sound settings and comes and goes rather
randomly. It sometimes persists even when the playback is paused. I can't
say when I first noticed it but I think it was when I went from Ben's bookmark
version to the first CVS merged version of the bookmark code. It might have
been when I flashed the code, as I did both in close proximity.
I have a set of computer speakers on my bedside table and first started
noticing the tone when I'd pause a book to go to sleep. If I happened to
pause when the tone was present I'd have to turn the speakers off to eliminate
I did go back to one of my backup Recorders that has Ben's next to last
pre-CVS release, non-flashed. The tone is not present.
On Sun, 29 Feb 2004 14:10:13 -0500 (EST), "John Donahue"
>I've been recording some old 78rpm albums to .wavs(CDquality) and then converting those to low fi, 16kbps mp3s through MusicMatch. Examination in Mp3DirectCut shows them to be mpeg2.5,layer3, 16kbps, 11kHz Mono.
>Anyway, they sounded fine, no loss in quality since not much to begin with, and I get that nice 1/90 compression ratio :) 8kbps was just too much of a squeeze.. even for 78's.
>They sound great that is on software players, musicmatch, mediaplayer, directCut, but on the archos(i have FMrecorder) and on a CDmp3 player(AudioPhase) there's that high tone of constant pitch accompanying the intended sound. There's no other sound difference - otherwise it's just as clear as the software players except the tinny whine. The music's midrange frequencies seem to bring it out most.
>And the problem occurs for all bit rates from 8 to 32kbps.. 40kbps is where the high tone immediately disappears, so its a shame to have to increase the file size by more than three times in order to lose the squeak.
John De Armond
Cleveland, Occupied TN
Page was last modified "Jan 10 2012" The Rockbox Crew