Some answers...

  It has to be a well compressed audio file that does not need to be
  lossless.

  It has to be USB and it is not tricky to combine two mics. Stereo is
  normal nowadays.

  It should be a small pcb.

  Pre-Processing should work using a mic preamplifier for each mike.

  Eventually costs have to be below normal voice recorders with
  line-in or mic cans.

> I've never done much with audio, but here are my initial thoughts:

> * Does it have to be mp3?  I'd use the much simpler .wav (google .wav
> spec to see how to implement it)

> * Does it have to be a USB stick?  I'd favor using a CompactFlash  
> card.  Again, the spec is much simpler to implement.  see "PIC a  
> CompactFlash Card" by Mark Samuels.

> * It'll be tricky to get two microphones recording at the same time  
> through the same PIC to the same CF card.  It'd be easier and cheaper
> to make two boards (the biggest sink is going to be your time and the
> PCBs anyway, and if you use a PCB service you'll have several of  
> those, anyway).

> * I know there are cheap high-sampling rate audio ADCs... check them  
> out on digikey.

> * I don't know what kind of pre-processing you'll need to do to the  
> Mic inputs...

> * By the time you get through all of this, are you really going to be
> beating (by whatever metric you're trying to beat them) a cheap-o  
> digital audio recorder?




Give me a link to this chip, please.


> There is a module that might be of interest.  I have also looked for a way
> to support audio.  While .WAV files are easier to deal with, their size just
> eats up memory.  I have found the VINICULUM VMUSIC2 (you can find them on
> the internet and I think one of the large catalog houses (Newark or Mouser)
> carries them) which has a USB port on it.... they ain't cheap but it is a
> pretty clean solution.
> 
> My audio requirements are near CD-quality.  I hope we hear other thoughts
> from PIC listers as I am interested in this topic myself.
> 
> Rich


Regarding Hector Martin:

At best, I want to load a given code into a pic, assemble a given
circuitry and make some design improovements if necessary. Then it is
to work. But I won't reinvent the wheel, recording to audio-files is
normal.

I am not used to dealing with audio-file-formats.


cheers all together

TK




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