Digital Sound

[threewheeler7]

i have a project in development that will require around 15 seconds of pre-recorded audio to be played back, it needs to be of fairly descent quality. i am using a mid-range PIC for the projects other functions. this will be my first micro controller based project with audio. i need some suggestions for some sort of inexpensive solution.  

[Olin Lathrop]

threewheeler7 wrote:
> i have a project in development that will require around 15 seconds of
> pre-recorded audio to be played back,

OK so far.

> it needs to be of fairly descent quality.

Now that's a totally useless statement.

There is no point suggesting schemes until you know what you want.

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[Bob Blick-4]

On Wed, 16 Jul 2008 15:17:21 -0400, "Olin Lathrop"
<olin_piclist@...> said:

> threewheeler7 wrote:
> > i have a project in development that will require around 15 seconds of
> > pre-recorded audio to be played back,
>
> OK so far.
>
> > it needs to be of fairly descent quality.
>
> Now that's a totally useless statement.
>
> There is no point suggesting schemes until you know what you want.

Stern stuff, but I have to agree. For instance, if you've listened to
the output from ISD chips and think that's good enough, that'd be
something to mention. Or if you've experimented with your PC and a
"decent" sound editor and reduced the number of bits(you can fake it by
doing a volume reduction and then raising it back up) and the
bitrate(you can fake it by doing pitch shifting a number of times and
then doing it the other way).

Or maybe just talking about it in terms of telephone/AM radio/etc
quality.

By the way, what did you think about all the servo driving ideas you got
in response to your question the other day?

Cheerful regards,

Bob

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[threewheeler7]

well Bob, the servo suggestions helped allot, i did not get a chance to post results yet.
i know that was way to vague, i have a fine line between price and quality, somewhere around 22khz would be ideal but i just don't know enough about the technology to have a grasp of what is possible(or, economical i should say).

[William "Chops" Westfield]

On Jul 16, 2008, at 12:17 PM, Olin Lathrop wrote:

>> it needs to be of fairly descent quality.
>
> Now that's a totally useless statement.
> There is no point suggesting schemes until you know what you want.

Does anyone have numbers to go with:
ISD quality.  Telephone Quality (56kbps!)  AM radio quality.  FM  
Radio Quality.

The "standard" scheme is serial flash memory of some type and an A-D  
converter.  You get to pick and trade bits and sample rate to get  
more or less quality with more or less memory.  At some point, you  
start looking at consumer "flash cards" for storage rather than  
chips.  Here's an open source design (and kit) designed to be used  
with AVR:

http://www.adafruit.com/index.php?
main_page=product_info&cPath=17_21&products_id=94

BillW

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[Bob Blick-4]

Sort of AM radio quality then. That can amount to quite a bit of memory
in 15 seconds. More than you could store in a 256 kilobit eeprom, even
compressed. And higher quality than the ISD chips provide. Maybe store
it in an SD card?

Cheerful regards,

Bob

On Wed, 16 Jul 2008 13:36:07 -0700 (PDT), "threewheeler7"
<threewheeler7@...> said:
> i know that was way to vague, i have a fine line between price and
> quality,
> somewhere around 22khz would be ideal but i just don't know enough about
> the
> technology to have a grasp of what is possible(or, economical i should
> say).


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[Richard Seriani, Sr.]

----- Original Message -----
From: "threewheeler7" <threewheeler7@...>
To: <piclist@...>
Sent: Wednesday, July 16, 2008 2:45 PM
Subject: [PIC] Digital Sound


>
> i have a project in development that will require around 15 seconds of
> pre-recorded audio to be played back, it needs to be of fairly descent
> quality. i am using a mid-range PIC for the projects other functions. this
> will be my first micro controller based project with audio. i need some
> suggestions for some sort of inexpensive solution.
> --

Several months ago I started, and am still intermittantly working on, a
similar design - just a little longer record time. I've used a 16F88 and,
later, a 16F883, and saved data to a 25LC1024 (1 Mbit SPI EEPROM). Using
MCP4821 DAC to recover audio. Not complete, but ...('excuses' not
necessary).

Check the archives under the subject: [PIC] A/D and D/A using PIC16F88
for the suggestions others provided to help me get this going/make it
better.

Good luck,
Richard

>


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[Nate Duehr]

Richard Seriani, Sr. wrote:

> Several months ago I started, and am still intermittantly working on, a
> similar design - just a little longer record time. I've used a 16F88 and,
> later, a 16F883, and saved data to a 25LC1024 (1 Mbit SPI EEPROM). Using
> MCP4821 DAC to recover audio. Not complete, but ...('excuses' not
> necessary).

Any reason not to use one of the well-tested, well-documented chips from
ISD that already do all this stuff?

Nate
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[threewheeler7]

so i address the memory of the flash memory with my PIC, and send the resulting bytes to an a/d? how would i get the uncompressed audio converted and on the flash? and when you are talking about using consumer flash cards, isn't that a whole other ballpark? i don't know i am just picking your brain.

William "Chops" Westfield wrote:

On Jul 16, 2008, at 12:17 PM, Olin Lathrop wrote:

The "standard" scheme is serial flash memory of some type and an A-D  
converter.  You get to pick and trade bits and sample rate to get  
more or less quality with more or less memory.  At some point, you  
start looking at consumer "flash cards" for storage rather than  
chips.

[threewheeler7]

just how much can you store on a 256 eeprom?
and do you know of a pre-built alternative, if i cannot get this to work soon?

Bob Blick-4 wrote:

Sort of AM radio quality then. That can amount to quite a bit of memory
in 15 seconds. More than you could store in a 256 kilobit eeprom, even
compressed. And higher quality than the ISD chips provide. Maybe store
it in an SD card?

[Olin Lathrop]

threewheeler7 wrote:
> somewhere around 22khz would be ideal ...

22KHz *what*?  Sample rate or bandwidth?  This makes a big difference.  And
you still haven't specified bits/sample.

Maybe you should describe the sound you are trying to reproduce and the
purpose of that reproduction.  Is it voice speaking directions someone just
needs to understand, or is it music that needs to sound like a live concert?


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[Olin Lathrop]

Bob Blick wrote:
> Sort of AM radio quality then.

Not if he's looking for 22KHz bandwidth.  That's more than most people can
hear and exceeds even FM quality.


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[Tomás Ó hÉilidhe-2]

William "Chops" Westfield wrote:
> Does anyone have numbers to go with:
> ISD quality.  Telephone Quality (56kbps!)  AM radio quality.  FM  
> Radio Quality.


CD quality music is 44.1 kHz with a sample size of 16 bits. That's 88.2
kB per second, or 1.3 MB for 15 seconds.

I'm sure you'd get away with 22.1 kHz, which would bring it down to
661.5 kB per second.

(B = bytes,  b = bits)

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[threewheeler7]

how far along is your project and what did you write it in?

Richard Seriani, Sr. wrote:

Several months ago I started, and am still intermittantly working on, a
similar design - just a little longer record time. I've used a 16F88 and,
later, a 16F883, and saved data to a 25LC1024 (1 Mbit SPI EEPROM). Using
MCP4821 DAC to recover audio. Not complete, but ...('excuses' not
necessary).

[threewheeler7]

ok what are these ISD chips you guys are talking about? what is the quality that they offer?

Nate Duehr wrote:

Any reason not to use one of the well-tested, well-documented chips from
ISD that already do all this stuff?

[Olin Lathrop]

threewheeler7 wrote:
> just how much can you store on a 256 eeprom?

Is this a trick question, like who is buried in Grant's tomb or what color
is my blue shirt?


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[Jan-Erik Soderholm]

threewheeler7 wrote:

> ok what are these ISD chips you guys are talking about?

www.isd.com
Or http://www.nuvoton-usa.com/en/content/view/36/
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[Bob Blick-4]

On Wed, 16 Jul 2008 22:32:00 +0100, "Tomás Ó hÉilidhe" <toe@...>
said:
>
>
> CD quality music is 44.1 kHz with a sample size of 16 bits. That's 88.2
> kB per second,

Actually double that since it's two channels.

Roughly speaking, the sample rate relates to the bandwidth, and the
sample size relates to the signal to noise ratio.

This has been discussed a lot on the piclist in the past, but you can
get away with some pretty low numbers especially if you carefully
process the sound.

And if you have enough processing power to spare you can store the data
compressed and save memory.

Cheerful regards,

Bob

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[Jinx-4]

> Sort of AM radio quality then.
>
> Not if he's looking for 22KHz bandwidth.  That's more than
> most people can hear and exceeds even FM quality

The ISDs are lower than AM quality. Depends on the particular
chip, but I don't think, from memory, any sample faster than 8kHz

The only really good IC is the long-obsoleted TMS3477/3478,
which used CVSD. Excellent bandwidth, not quite FM radio but
pretty close. Now that micros have advanced so much I'm trying
to emulate what it does

It is pretty memory-hungry. The 3478 can interface with DRAMs
(eg 4 * 4C1024) to get about 45s playback, although I have them
running with large SRAM and EPROM too. I'd like to do what it
can do with PC RAM or Flash using a PIC

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[Richard Seriani, Sr.]

----- Original Message -----
From: "Nate Duehr" <nate@...>
To: "Microcontroller discussion list - Public." <piclist@...>
Sent: Wednesday, July 16, 2008 5:18 PM
Subject: Re: [PIC] Digital Sound

> Richard Seriani, Sr. wrote:
>
>> Several months ago I started, and am still intermittantly working on, a
>> similar design - just a little longer record time. I've used a 16F88 and,
>> later, a 16F883, and saved data to a 25LC1024 (1 Mbit SPI EEPROM). Using
>> MCP4821 DAC to recover audio. Not complete, but ...('excuses' not
>> necessary).
>
> Any reason not to use one of the well-tested, well-documented chips from
> ISD that already do all this stuff?
>
> Nate

Yes. When I originally looked at the ISD chips, even their max record time
was too short by hours. The ultimate goal was to learn to do the A/D and
D/A, then increase storage time by using SD card(s).

Haven't looked at ISD in awhile. Can they do that?



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