Hi,

I'm doing recordings of FM broadcasts and want to set a lowpass filter of 15kHz since that's the maximum frequency response of my tuner.

However it seems that in LAME 3.93.1, if i set --lowpass to 12 or greater (i tried up to 26), the transisiton band is always the same: 11114 Hz - 11381 Hz (a setting of 11 does lower the transition band)

So, does this mean my maximum lowpass filter is actually 11kHz? (or is this some internal thing i don't understand and 15 is indeed different than 12)

Please clarify!

Thanks,

Jon

Perhaps your file is resampled to 24kHz because of your target bitrate?

Try --resample 44100. Then you will be able to higher the --lowpass value.

I tried encoding at a higher bitrate and sure enough, now i see a 15KHz transisition band.

I'm i bit perplexed at this. One one hand 44.1kHz is the sample rate, yet even so I can only assume that the frequency response is in the 20 something kHz range. So i don't see how these correlate

so why on a 22050 recording i can only set a lowpass of 11kHz? Does that mean a 22050 recording only has a freqency response up to 11kHz?

Can someone explain this to me?

Thanks,

Jon

- Your source file's sampling rate is 44.1 kHz.
- By default, that source file is resampled on-the-fly by LAME, because it's more efficient for the low encoding bitrate you're probably using.
- The maximum frequency in a 22kHz WAV file is 11kHz (the Nyquist frequency).


Correct. Also, for a 44.1kHz WAV file, the maximum frequency properly stored would be 22.05 kHz.

The order of arguments in the commandline makes a difference.

Perhaps you have the lowpass argument before your resample argument? Try putting the lowpass argument at the very end of the commandline.