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the use of "-k" switch in LAME 3.97a11, the use of Full Bandwidth mode or preset
Blenvid
post Aug 17 2005, 18:52
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Hey everyone,

I've been exhaustively reading all of the posts here and on the net this week trying to find an answer for this, but I haven't found one. I'm new to the ripping of cds with EAC (version 0.95) and encoding with LAME (version 3.97a11), but have been ripping music to create mp3s since 1997.

I noticed while encoding some mp3s with EAC and LAME that LAME said it was using a lowpass filter. I was simply using the preset "--preset standard" in EAC to pass to LAME. I then noticed that all of the mp3s I ripped with this preset used the lowpass filter. It's called the "polyphase lowpass filter."

Just to include the defenition of a lowpass filter for those that don't know what it is, it's a filter that attenuates (reduces in level) the frequencies above its cutoff frequency.

I looked around the web and found a couple examples of mp3s that were ripped with a LAME encoder at lower bitrate settings and there were some very high frequency artifacts which were created by the encoding process. I'd imagine the lowpass filter was included to reduce one's ability to hear these artifacts.

If you take a look in the LAME "Full command line switch reference" document included with LAME, it says under the "-k" switch that the Full Bandwidth setting "tells the encoder to use full bandwidth and to disable all filters. By default, the encoder uses some highpass filtering at low bitrates, in order to keep a good quality by giving more bits to more important frequencies. Increasing the bandwidth from the default setting might produce ringing artefacts at low bitrates. Use with care!"

Why would anyone want to put filters on their music if they're using the LAME "--preset standard" setting which isn't even a lower bitrate setting, but has bitrates in the 170 to 210 kbps range? blink.gif

To test, I went ahead and put "-k" in my command line; the resulting command line looked like this, "--preset standard -k" without the quotes of course. I want all of my mp3s to be in Full Bandwidth, not with filters. I noticed that the files with the -k switch sounded a little more open, more transparent, a little more like the original, yeah!!!

What's the word from anyone else on LAME's default filters using the "--preset standard" preset? The LAME recommended settings everywhere don't even mention this. Because we're using a higher bitrate, wouldn't you want your mp3s to be at Full Bandwidth as well, without any filters? I've noticed that some people like to put bass boost filters on, but people who just want the music as close to it was on disc? Why aren't people using the -k switch? huh.gif

Thanks for any input.

-Blenvid
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