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missing frequencies/sounds >16kHz using lame 3.99.4-64
shmick23
post Feb 26 2012, 14:51
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hi,

i recorded some vinyl using Goldwave 5.25 under win 7 pro x64 and saved the files as a 24/96 un-compressed Windows Wave file.

i had a look at the frequency representation in Adobe Soundbooth CS5 and noted that the max. freq. attained was around ~27kHz (which seems acceptable given my sound card, cartridge and phono stage).

i then compressed the file using Foobar2000 1.1.9 to a lame mp3 with the settings:

Audio
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Mode : Joint stereo
Duration : 5mn 51s
Bit rate mode : Variable
Bit rate : 282 Kbps
Minimum bit rate : 32.0 Kbps
Channel(s) : 2 channels
Sampling rate : 48.0 KHz
Compression mode : Lossy
Stream size : 11.8 MiB (100%)
Writing library : LAME3.99r
Encoding settings : -m j -V 0 -q 0 -lowpass 24 --vbr-new -b 32

having a look at the frequency representation again in Soundbooth showed a reduction/cutoff above 16kHz for certain sounds (not all).

Why is this and how (if possible) could I retain these upper frequencies ?
I assumed since the mp3 is a 48kHz file each channel should contain up to 24kHz sounds - from the graph it does, but only for certain sounds, and others are removed >16kHz

Also, is it a default setting by either foobar/lame to use lowpass by default ?

i've uploaded some screen grabs for visualisation:










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shmick23
post Feb 28 2012, 17:17
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Jaz: thank you & noted for bitwidth and raw files, I thought that these settings were referring to the input file

dvddoug: primarily horns, sax, vocals are the frequencies i wish to preserve as much as i can, it would be fine for me if, what you say, the lower frequencies were thrown out more compared to the higher ones (if this is what occurs by forcing lame to retain higher ones). I still have a little confusion about this process and will need to read up more on how this is dynamically achieved at compression time.

kohlrabi: i appreciate the link, this will take a while to digest, im not archiving just 'yet.' i'll need to invest a little more in equipment

again, thank you for the responses.

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dhromed
post Feb 28 2012, 17:55
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QUOTE (shmick23 @ Feb 28 2012, 17:17) *
primarily horns, sax, vocals are the frequencies i wish to preserve as much as i can


Those are all mid-low frequencies that barely make 10KHz, so you're safe. You preserve them as much as you can with the 16KHz lowpass.

QUOTE
if this is what occurs by forcing lame to retain higher ones)


Nope.
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