AVR-Chat

Hi Jesper,

Raw sampling is a possibility I'm considering but then it's not possible to
load the file into a PC for example without storing it as WAV or something
similar.

I think 8 KHz sampling rate is not enough to create a sound like one would
expect from a tape recorder/MD or similar device.

What if I "only" needed 16 KHz sampling from a 16bit DAC connected to the
SPI or XMEM interface and stored that onto the card on the fly and then
loaded one of the 16bit timers with the recorded result and forwarded
through the "record buffer" with 16KHz wouldn't that work ?

I have never tried to use the onboard 16bit timer for audio generation 
Is it possible to get a decent "sound" out of an RC filter being pulsed with
PWM? 

Best regards
Lasse Madsen





-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Jesper Hansen
Sent: 22. august 2005 12:29
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] OT: Sound record/playback

Do you really need to encode it ? Why not just store the raw samples ?
You can use the internal A/D for sampling, and playback with PWM.
A dual op-amp can be used as a microphone pre-amp.
Assuming a 8-kHz sample rate (you didn't say what quality you needed),
you'd only need to store 1 (or perhaps 2 if you use more that 8-bit 
resolution
from the internal A/D) per sample => 8000 bytes per second.
That like a walk in the park for an AVR.

For MP3 encoding/decoding, look at the Micronas MAS3587.

/Jesper

> I'm facing a new challenge that I haven't tried to solve before and I 
> would
> like some input if anyone has tried this before. I need to record and
> playback voice/sound from a microphone and store it on a Secure Digital 
> card
> with FAT16 file format, which is no problem, but what I would like some
> input on is what "front end" IC I could use to maybe do the MP3 encoding 
> so
> that I only have to "cheat" and store the pre encoded signal on the SD 
> card
> and be able to play it back again.
>
>
>
> I was thinking of using maybe a IC like this:
> http://www.analog.com/UploadedFiles/Data_Sheets/76229755AD73311L_a.pdf
> although it does not have the capacity to encode/decode MP3, I could use 
> it
> for both encoding and decoding my raw audio signal, but what I can't
> determine is if I'm able to store the data as fast as it samples with
> 64/32KHz onto the SD card.
>
>
>
> I know that Micronas makes some kind of MAS de/encoder for MP3 but have
> anyone had success with it?
>
>
>
> Best regards
>
> Lasse Madsen
>
>
>
> /My current knowledge doesn't enable me to use DSP processors as I've 
> never
> worked with them before and now is not the time to start unfortunately.
>
> 




 
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