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Subject: low-fi mp3s
From: John Donahue (john.donahue_at_excite.com)
Date: 2004-02-29


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.

What's the difference between the softwares' method of playback and rockbox's? I noticed that I can create the problem in Windows MediaPlayer by changing the frequency quality in the filter properties from 'full' to 'half'.

Is it possible to improve the playback for files in this 8-32k range? or is it an mpeg2.5 issue that cannot be fixed through firmware?

I posted some sine wav examples and a James P Johnson tune for examination at: http://kentucky.home.att.net

Thanks for any help and info,
JohnD

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