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Topic: --standard problems (Read 4119 times) previous topic - next topic
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--standard problems

I recorded a show from the radio last night. As a 44.1 Khz/16 bit wav file.

As FM radio does not go beyond 16Khz (as far as I remember) I want to lowpass my MPC file exectly there. So I add "--bw 16000" to my command line, making it "--standard --xlevel --bw 16000".

Upon encoding mppenc says: "SV 7.0 + XLevel coding, Profile 'Radio'".

I've encoded thousands of MPC files, but I've never tinkered with the switches like this, so I don't have much experience in this direction. But why does it say Profile 'Radio', when I specified --standard on the command line?

Using mppenc 1.15r by the way.

--standard problems

Reply #1 –
Because you're messing with the internal settings. It's not a 'real' standard file.

Have you verified whether the lowpass actually makes any difference? mppenc should be smart enough
to see there's no >16kHz data.

--standard problems

Reply #2 –
There is no data >16 Khz. Only noise.

Tested both with and without the lowpass.

Bitrate with --bw: 166.3 kbps, filesize: 64.919.128
Bitrate without --bw: 173.1 kbps, filesize: 67.542.136

As Case said on IRC, the only thing that changes is the profile name, which get set to Unstable/Experimental anyways. So it's not really a problem.

--standard problems

Reply #3 –
Hi,

I often rip Tapes to my PC and encode them then. So could I use 18khz Lowpass Filter? Because my deck doesn't support Frequences above 18khz at normal band.

And btw when using Lame encoder, can I also change the lowpass filter or does this make the quality worse?

--standard problems

Reply #4 –
I'd prefer to apply the lowpass during the post-recording process in Cool Edit Pro (or whatever you use), so the encoder will have the chance to detect that there is now data above 18khz itself.
dev0
"To understand me, you'll have to swallow a world." Or maybe your words.

--standard problems

Reply #5 –
Quote
I often rip Tapes to my PC and encode them then. So could I use 18khz Lowpass Filter? Because my deck doesn't support Frequences above 18khz at normal band.

And btw when using Lame encoder, can I also change the lowpass filter or does this make the quality worse?

With LAME APS, sure you can lower the low-pass for music with no HF content, but don't increase it (above 19.0 kHz) for normal music because this may give no audible benefit and even cause artifact problems due to the inefficiencies of MP3's VBR implementation that might cause it to run out of bits when it really needs them.

As for tapes and MPC, your tape deck may say it's flat within 3 dB or 6 dB up to 18 kHz, but it might still have some >18 kHz content, albeit reduced, especially on Metal tapes, for example. If you record to WAV first, any WAV editor in spectral view will show you pretty much where the cut-off lies.

Now, MPC standard should be transparent, so if the sounds at 18kHz and above are inaudible it won't record them (if they're almost audible it might do it to be safe). Of course, it may include a little bit of tape hiss at 18+ kHz when there's no musical content there, so you may improve perceived noise by a really tiny amount by lowpassing.

--standard problems

Reply #6 –
What happens if you use a quality level instead of a profile name?
 

--standard problems

Reply #7 –
I think FM radio cuts off at 15KHz not 16KHz.