Subject: Re: [linux-audio-user] Wave file conversion (multi-mono->stereo, then downsample/downsize, then dither)
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Fri Sep 10 2004 - 11:46:17 EEST
On Thu, Sep 09, 2004 at 01:57:17 -0700, Mark Knecht wrote:
> On Thu, 2004-09-09 at 13:35, Steve Harris wrote:
> > On Thu, Sep 09, 2004 at 01:22:45 -0700, Mark Knecht wrote:
> > > I do have libsamplerate installed on my laptop here in the office.
> > > Since all of this is just file manipulation I can do everything here and
> > > then listen elsewhere. (Onboard sound works, but is not so good.
> > > Interesting bass distortion problems even at VERY low levels when
> > > playing with Jamin this morning. I hope that's not Jamin itself...)
> >
> > JAMin has had problem with bass distortion in the past, if it is JAMin
> > please supply some test material and I'l look into it - OTOH if youre
> > using linear interpolation - stop it! :)
>
> Steve,
> I'll fire it back up this afternoon and look for linear interpolation
> options. I was simply in a default set of settings, other than using the
> solo button to hear the individual bands. The bass bands had very little
> energy, according to the spectrum analyzer, and the overall levels were
> set VERY low - like -20db, but I was still hearing noticible breakup.
Oh, I didn't mean in JAMin, JAMin doesnt do interpolation, I meant in
opther parts of the chain.
> Maybe I can just record it in Ardour and send you that?
The actual sound wont help, I really need the ingredients to recreate it
I'm afraid.
> One other possibility, I suppose, is that the problem is there on the
> original tracks. I did the tracking at 96KHz in Pro Tools and hadn't
> noticed any problems, but I wasn't searching either. Import to Ardour
> converts them to 44.1KHz as my laptop doesn't do 96K. Possibly the
> problem is in the conversion, or in the originals but masked somehow. To
> check that I'll have to listen closely in Pro Tools this evening.
Sometimes bringing up the average level in JAMin can be just enough to
reveal problem that were masked by other frequencies before, but dont rul
out a JAMin bug.
> > > Anyway, If I'm going to downsize from 24-bits to 16-bits then I want
> > > to add dithering, but I see no mention of dithering in man ecasound. I
> > > know jack has an option to dither it's outputs, but from some dark
> > > remote part of my memory I seem to remember that this only effects the
> > > output going to the sound card and not what's going to a file. Comments
> > > anyone?
> >
> > Thats right. Soundcard only.
>
> So is there any solution to dithering a final output? I think we talked
> about this recently, but the answer eludes me. If there is a dither
> plugin I couldn't find it. I was supposing that the 24-bit output could
> be dithered to 16 bits but saved as 24-bits, and then maybe the bottom 8
> bits just get stripped at the command line or something like that.
Ardour can dither, so if you record the output of JAMin into ardour and
export from there you should be able to save down as 16bits.
- Steve
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