Re: Re: sound APIs/programming

On Jul 10, 2005, at 5:24 PM, Seth Cameron wrote:

> I do not think that separate left volume/right volume control  
> (balance) is
> possible using aumix without the ncurses interface. Is that true?

I believe it is -- certainly I implemented left/right balance, bass/ 
treble boost and I think maybe one or two other similar things in the  
ucb1400 driver, and the only way I had to test was using aumix -- so  
I think it is possible.

> Also, recording using brec should be done stereo even though the  
> mic is
> mono. Mono settings with brec will write an incorrect .wav header  
> and only
> record for 1/2 as long as requested.

Yeah, ucb1400 seems to be doing something "special" with the duped  
mic input or something, and I think it confuses brec somehow.  Not  
sure what's going on exactly.

> This brings me back my original query about decent quality microphone
> recordings.  I've been able to make reasonable recordings from line  
> in CD
> sources, but all of my attempts at microphone recordings have  
> significant
> hiss and poor gain. (Similar to the type of voice recordings one  
> can make
> with, for example, an IPAQ using the built-in mic.)
>
> Has anyone had success making good S/N microphone recordings?
>
> If not, my conclusion at this point is the that the preamp on the  
> UCB1400 is
> crap, or significant digital noise is creeping into the audio  
> circuitry,
> probably both.

Hmm, testing I was doing sounded OK -- not audiophile OK since I  
wasn't listening for that, but "sounds at least as good as I'd expect  
from my $10 microphone" OK.  It wouldn't substantially surprise me if  
the pre-amp were lousy on the usb1400, which seems like the most  
likely problem if you say line-in input is OK.  Might be useful to  
look at a sonogram of the noise though, to see if it looks like  
there's a dominant frequency which might point to noise leaking.

> I'm looking at using a separate battery powered mic preamp, but the  
> smallest
> I can find is bigger than gumstix and requires 9 V. :-) So much for
> miniaturization....

I think while I was looking around at mics for testing, that I saw  
some reasonably small powered mics.  Could easily be that the  
websites I was looking at though were just showing the mic head and  
not showing the giant battery pack box...  I'll see if I can find  
those sites again to provide links when I get back online here...

C


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