[music-dsp] OT: CD Perfection

Erik de Castro Lopo erikd-music-dsp at mega-nerd.com
Mon Oct 18 16:41:19 EDT 2004

On Sat, 16 Oct 2004 07:13:19 -0500
RTaylor <ricktaylor at speakeasy.net> wrote:

> You should be able to hear it fairly clearly. Rezound has a noise 
> generator... you might try that. As far as measuring it goes... I have
> no idea. Is there something out there that will measure "crispness"? :} 
> {Is "crispness" something thats going to matter to most of your users?}

OK, I tried this. I didn't use Rezound because last time I tried it
didn't work on my PowerPC linux system.

Instead, I generated uniform distributed white noise in Octave (GNU
MATLAB clone) saved the data as a mono 48kHz floating point file and 
loaded it into Sweep. In Sweep, I did the following:

   - resample from 48kHz to 44.1kHz
   - normalize the resampled audio, because the resampling can 
     introduce peaks that go outside the [-1.0, 1.0] range.

using both the best quality and fastest Sinc based converters that
Secret Rabbit Code provides. I simply could not hear any difference.

I'm doing my listening test on a pair of high quality headphones
plugged into the output of my TerraTec DMX6Fire card (24 bit, 96kHz
capable card).

Now I'll be the first to admit that I no golden-ears, but neither
is my hearing in the least bit faulty in comparison to the average
person of may age (40ish).

As part of this experiment I also used the linear interpolation rate 
converter included in Secret Rabbit Code and then I could hear a
difference. The difference was an attenuation of the high frequencies
which is exactly what I would expect. One might describe this as a 
lack of crisp-ness.

So, I would like to know which converter (out of the 5 that Secret 
Rabbit Code provides) you were using when you did your listening tests.

  Erik de Castro Lopo  nospam at mega-nerd.com (Yes it's valid)
Journalist: Microsoft CEO Steve Ballmer has finally said Linux
            is the No. 1 threat to Windows. What's your response to that?
Linus     : "Tag, you're it." I don't care. They've had a lot of
            enemies in their time. Let them fight one enemy that
            doesn't care for a change.
  Erik de Castro Lopo  nospam at mega-nerd.com (Yes it's valid)
"Crap can work. Given enough thrust pigs will fly, but it's not necessary a
good idea."  -- Alexander Viro on linux-kernel mailing list

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