Spectrogram for flac files?

Berticus · 2009-08-16 23:21:54

I know there's an R script to produce frequency response and spectrograms for flac files, but I was wondering if there were any other way. I have a burned CD I would like to verify that it was a copy of a CD and not an Audio CD made from mp3's.

.:B:. · 2009-08-17 07:00:45

Audacity?

Berticus · 2009-08-18 03:25:01

Oh, didn't realize Audacity had a spectrogram feature. Don't use it much... or really at all.

Thanks, B.

.:B:. · 2009-08-18 08:25:15

You're welcome. For reference, here are some typical spectrals for common encoding formats:

FLAC:

http://img462.imageshack.us/img462/8946/flacvv2.png

MP3 LAME 128 kbps:

http://img462.imageshack.us/img462/4782/128lamewl3.png

MP3 LAME 160 kbps:

http://img223.imageshack.us/img223/2971/160lamenf8.png

MP3 Fraunhofer 160 kbps:

http://img462.imageshack.us/img462/3716/160fhgsy4.png

MP3 LAME 192 kbps:

http://img160.imageshack.us/img160/5825/192lamejs9.png

MP3 Fraunhofer 192 kbps:

http://img462.imageshack.us/img462/5137/192fhgcf0.png

MP3 V2/APS kbps:

http://img473.imageshack.us/img473/77/v … ardxj0.png

MP3 V0/APX kbps:

http://img462.imageshack.us/img462/3979 … emels8.png

Typical web rip:

http://img160.imageshack.us/my.php?imag … ripfp7.png

Comparison between different rips:

http://img473.imageshack.us/img473/2159 … areum0.gif

Analysis
As you can see, LAME uses 'full resolution' up to the frequency threshold, whereas FhG, encodes at 'full resolution' up to 16kHz, and uses 'low resolution' at higher frequencies. This is an easy way to tell which encoder was used. At 128kbps, LAME uses a LPF at ~17kHz and FhG at ~16kHz. I have included a screenshot of FhG at 128kbps without the LPF. At 160kbps FhG's LPF is set at 20kHz. At 192kbps, LAME stops at 19kHz and FhG encodes upto 22kHz.
FhG looks like it's not doing its job right, but if you listen to the 192kbps samples, you can hardly tell which is LAME and which is FhG. At 128kbps, LAME sounds a bit better, more 'clear'. FhG encoding at 128kbps without the LPF sounds bad, you can certainly listen to the artifacts.
LAME APS will typically use a LPF at 18.5kHz, whereas APX will go up to 19kHz.

More info on the subject can be found on the Head-Fi forums .

Arch Linux

#1 2009-08-16 23:21:54

Spectrogram for flac files?

#2 2009-08-17 07:00:45

Re: Spectrogram for flac files?

#3 2009-08-18 03:25:01

Re: Spectrogram for flac files?

#4 2009-08-18 08:25:15

Re: Spectrogram for flac files?

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