Yes, it's kind of interesting. The application is a game which needs numbers
to be read plus a number of sound effects. Perhaps unsurprisingly sound
effects are fine at 4.8Ksps and 4bit sampling. Human speech is best at over
6ksps and 8 bit sampling - below this intelligibility suffers hugely.

I would investigate more efficient schemes but the advantage of straight PCM
is that it is really easy to decode and I can't afford a big processor
overhead.


Robin Abbott
Forest Electronics
robin.abbott@fored.co.uk
www.fored.co.uk 
 

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
William "Chops" Westfield
Sent: 30 September 2007 22:59
To: Microcontroller discussion list - Public.
Subject: Re: [PIC] Talking PIC's !


On Sep 30, 2007, at 1:28 PM, Robin Abbott wrote:

> I've created a system based around an 8 pin external EEPROM storing up 
> to 256K bytes sampled.
>
>  About 10 seconds of speech and sound effects can be held with 
> reasonable quality.

Clever use of resource to be able to use the internal HW.

But 10 seconds in 256kbytes is pretty bad, storage wise.  "Telephone
quality" is normally 64kbits/second, with "acceptable voice quality"  
down around 8kbits/sec with relatively trivial compression schemes...  (I
suppose this could just be due to your choice of .WAV file format, rather
than limits of the playback scheme.  Have you fiddled with the encoding
parameters to see where quality begins to
"suffer."?)

BillW
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