Procedure:
1. I generate 1KHz sinus -90db test signal with wavosaur 1.0.0.9000.
File: "sinus 1kHz -90dB.wav"
Format 24-bit mono wav
Playing with SQ3: OK
2. I encode "sinus 1kHz -90dB.wav" to mp3 with lame 3.97
command: lame --preset insane "sinus 1kHz -90dB.wav" "sinus 1kHz
-90dB.wav".mp3
resulting File: "sinus 1kHz -90dB.wav.mp3"
Format MP3
Playing with SQ3: strange arthefacts in sound louder then test signal,
very weird
3. Now I decide to decode MP3 on PC and play decoded wav file on SQ3.
I decode "sinus 1kHz -90dB.wav.mp3" on PC with 2 mp3 decoders:
A. Lame
command: lame --decode "sinus 1kHz -90dB.wav.lame.mp3" "sinus
1kHz
-90dB.wav.lame.mp3".lame16.wav
resulting File: "sinus 1kHz -90dB.wav.lame.mp3.lame16.wav"
Format 16-bit mono wav
Playing with SQ3: Distorted 1Khz (no dithering), OK for decoder
without 24 to 16 bit dithering
B. Mad 16 bit
command: >madplay -v -b16 -owav:"sinus 1kHz
-90dB.wav.lame.mp3".mad16.wav "sinus1kHz -90dB.wav.lame.mp3"
resulting File: "sinus 1kHz -90dB.wav.lame.mp3.mad16.wav"
Format 16-bit mono wav
Playing with SQ3: Clean 1Khz with dithering noise, OK for
decoder
with 24 to 16 bit dithering
C. Mad 24 bit
command: >madplay -v -b24 -owav:"sinus 1kHz
-90dB.wav.lame.mp3".mad24.wav "sinus1kHz -90dB.wav.lame.mp3"
resulting File: "sinus 1kHz -90dB.wav.lame.mp3.mad24.wav"
Format 24-bit mono wav
Playing with SQ3: Clean 1Khz without noise just like original
file,
OK for full 24-bit decoder
Additionaly, I normalized wavs to -6dB to hear diferences without
extreme amplification:
Normalized -6dB wavs:
"sinus 1kHz -90dB.nor -6dB.wav"
"sinus 1kHz -90dB.wav.lame.mp3.lame16.nor -6dB.wav"
"sinus 1kHz -90dB.wav.lame.mp3.mad16.nor -6db.wav"
"sinus 1kHz -90dB.wav.lame.mp3.mad24.nor -6dB.wav"
Of course, to hear how SQ3 play problematic mp3 you must listen SQ3
directly with extreme amplification.
4. Conclusion
Built-in MP3 decoder in SQ3 is problematic/flawed with some files, PC
MP3 decoders (MAD and Lame) decodes that files correctly.
Polite request to Sean Adams/Slimdevices: please fix it, best to
implement full 24-bit MAD decoder
as stated on Squeezebox product info web page:
http://www.slimdevices.com/pi_squeezebox.html
# MPEG decoding uses MAD software, widely regarded as the most
accurate, most compatible MP3 decoder.
# High accuracy 24-bit synthesis
# Supports all MP3 data rates and sample rates, including VBR
5. Someone please test this procedure on your system, to verify my
facts.
If someone have sound card with s/pdif in please capture output from
SQ3 when playing problematic mp3 file
("sinus 1kHz -90dB.wav.mp3") for further analysis.
Remarks
-my system: windows Xp SP2, slimserver 6.5.3
-all wavs are 44.1KHz
-all files except normalized are extremly quite, to hear something you
must amplify to the max,
I use SQ3 on 100% volume + headphone Amp with 11x amplification on
Sennheiser HD580
please be very carefull when work with maximum volume beacuse you
can easily damage your ears/equipment,
start with low volume, then gradualy amplify
-Used free software links:
Wavosaur free audio editor
http://www.wavosaur.com/download.php
LAME 3.97 release
http://www.rarewares.org/dancer/dancer.php?f=lame-current
MADPlay v0.15.2b Command Line mp3 Player/Decoder
http://www.rarewares.org/files/mp3/madplay-0.15.2b.zip
All files mentioned here are available in zip file on link:
http://www.mytempdir.com/2064518
contens of zip file:
Directory of c:\slim\zip\t
20.11.2007 14:19 <DIR> .
20.11.2007 14:19 <DIR> ..
20.11.2007 14:00 3.469 description.txt
03.10.2006 14:33 520.192 lame.exe
20.11.2007 09:02 31 lame16.cmd
20.11.2007 09:01 35 lameencode.cmd
20.11.2007 09:09 39 mad16.cmd
20.11.2007 09:10 39 mad24.cmd
23.08.2004 10:09 137.728 madplay.exe
20.11.2007 14:19 <DIR> normalized
20.11.2007 08:35 3.969.564 sinus 1kHz -90dB.wav
20.11.2007 09:01 1.202.676 sinus 1kHz -90dB.wav.lame.mp3
20.11.2007 12:04 2.647.434 sinus 1kHz
-90dB.wav.lame.mp3.lame16.wav
20.11.2007 09:09 2.649.644 sinus 1kHz
-90dB.wav.lame.mp3.mad16.wav
20.11.2007 09:11 3.974.444 sinus 1kHz
-90dB.wav.lame.mp3.mad24.wav
20.11.2007 14:19 0 t
20.11.2007 09:00 311 Urls.txt
30.06.2007 23:49 458.752 Wavosaur.1.0.0.9000.exe
15 File(s) 15.564.358 bytes
Directory of c:\slim\zip\t\normalized
20.11.2007 14:19 <DIR> .
20.11.2007 14:19 <DIR> ..
20.11.2007 13:43 3.969.564 sinus 1kHz -90dB.nor -6dB.wav
20.11.2007 10:27 2.647.954 sinus 1kHz
-90dB.wav.lame.mp3.lame16.nor -6dB.wav
20.11.2007 10:25 2.650.164 sinus 1kHz
-90dB.wav.lame.mp3.mad16.nor -6db.wav
20.11.2007 10:28 3.975.050 sinus 1kHz
-90dB.wav.lame.mp3.mad24.nor -6dB.wav
--
sikahr
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