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Converting FLAC to MP3 - strange cutoff frequency only when using FB2K
post Feb 10 2013, 03:53
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Hi, guys, ran into a weird problem and decided to share it with you, hope you can explain this to me. I was converting several lossless rips of albums in FLAC to MP3 (@ 320 CBR) and when checking the spectrogram of one of the resulting files I was quite shocked at what I saw. The song I'll use as an example here is called "Mutant", it's the third song from the album "HyBreed" by the Norwegian industrial metal band "Red Harvest".
Here's the spectrogram of the FLAC file:

I use foobar2000 as a front-end with the latest LAME version (3.99.5), downloaded from RareWares. In the "Converter Setup" I choose MP3 (LAME) at 320 kbps CBR as output file format. After the encoding finishes what I get is an MP3 file with a spectrogram that surprisingly looks like this:

Why is the frequency cutoff at 14-15 kHz, this looks worse then most 192 kbps encodes?! If someone checked this he would probably think this is a re-encode or web-rip. Now I guess some people might say this is theoretically possible, depending on the specifics of the music the encoder might decide to filter those frequences and so on, but this is clearly not the case and here's the proof (surprise, surprise). When I use the same encoder and settings, but a different front-end (All2LAME) I get an MP3 file with this spectrogram:

So is foobar2000 doing something wrong or am I missing something or what? blink.gif
Same thing happens with some other songs by Red Harvest, but not all - for most of them it's the usual for 320 CBR ~20 kHz cutoff, but for some like this one it strangely drops to almost 14.

This post has been edited by ChesterB: Feb 10 2013, 03:54
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