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'codecs'
1996\06\01@124112 by Stuart Allman

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I have yet another dilema to pose.  I need to have two A/D's and four D/A's
on this project.  I was thinking about using two codecs, but I can't find
one that meets or beats high end audio needs.  It seems like most of them
are made for computer related audio where noise level is not a priority.
When I amplify the signal to 100 watts this will be a real problem for me.

Does anyone have any recommendations on parts I could use with a 2101 or
2105 DSP.  I've heard that Crystal makes some really nice Codecs that could
meet CD quality standards.  Price is not the main issue, but no $100 parts
please, I'm still a student.

Stuart Allman
Studio Sound Design
spam_OUTstudioTakeThisOuTspamhalcyon.com

'crystal codecs'
1996\06\17@123621 by Stuart Allman

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Does anyone know how to get ahold of a rep from crystal semiconductor.  A
northwest US rep would be optimal.  I tried e-mailing their support
address and I haven't received a reply.

Stuart Allman
.....studioKILLspamspam@spam@halcyon.com


'crystal codecs'
1996\08\29@115940 by Stuart Allman
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Has anyone ever tried to initialize a crystal codec with a PIC.  I'm
trying to do this, but I don't know if it's working because I can't feed
samples through until the codec it initialized.


'Codec'
1999\08\29@093844 by Duilio Foschi
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what does "codec" means ?

Thank you

Duilio Foschi

1999\08\29@102525 by Steve Thackery

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Coder - decoder.  In the old days a codec was a piece of hardware - a chip.

A codec is typically an A/D (analogue to digital) converter plus a D/A
converter in the same package.  But they usually add extra functionality
such as implementing a non-linear coding regime (such as A-Law or mu-Law),
or other more sophisticated compression techniques.  Originally they were
for use in the telecommunications industry.  For example, the analogue
speech on your phone line is converted to/from a 64kbits/second data stream
by a codec on the line card in the exchange.  All such codecs implement a
non-linear coding regime, typically squeezing a 12-bit signal to noise ratio
out of an 8-bit-per-sample data format.

In more recent years the software codec has appeared.  You can best think of
these as an "engine" which converts a data stream from one format into
another.  Typical uses are for decoding video or sound data streams in
various formats.

Steve Thackery
Suffolk, England.
Web Site: http://www.btinternet.com/~stevethack/

1999\08\29@103404 by Bob Drzyzgula

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"Coder/decoder" or "compression/decompression algorithm",
in the same spirit as a modem is a "modulator/demodulator".

BTW, many tech sites have good glossaries; Cnet's
is at http://www.cnet.com/Resources/Info/Glossary/ ,
CMP's is at http://www.techweb.com/encyclopedia/ .
Most of them can answer many questions like this.

--Bob

On Sun, Aug 29, 1999 at 03:37:23PM +0200, Duilio Foschi wrote:
> what does "codec" means ?
>
> Thank you
>
> Duilio Foschi

--
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bobspamKILLspamdrzyzgula.org                until something bad happens
============================================================

1999\08\30@080119 by Wilson Tam

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Hi there, in communications, a CODEC is a section which converts analog
audio signals from microphone into digital signals for a vocoder. You
would fine CODECs in cell-phones which uses the CDMA modulation scheme.
It's the interface between the human side (microphone and earpiece) and
the CDMA side.

Wilson


On Sun, 29 Aug 1999, Duilio Foschi wrote:

> what does "codec" means ?
>
> Thank you
>
> Duilio Foschi
>


'PCM CODEC on a PIC'
2000\03\29@101837 by Terry
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Hi all

Been looking around for a single channel Voice/Audio CODEC and was
wondering if it might be possible to implement a CODEC in a PIC (or Scenix).

PCM would be prefered and without an external integrator (if possible but
the DAC part would probably require 1-2 Op amps for decent sound so.... ).
Anyone with anything to share on this?

Cheers
Terry


'[EE]: Voice codec ic's'
2003\06\27@141525 by Alex Harford
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Hello PicListers,

I'm looking for a low bandwidth voice codec solution that's easy to interface to a microcontroller.  It's going to be for a small commercial run, and I'm having trouble finding a reasonable solution.

A single chip would be best, but I'm open to using a DSP as well.  I've been talking to some people about licensing a DSP algorithm, but the ~25,000 US fee is a bit much.

We'd like to keep our bandwidth around 8k, with toll quality (MOS ~3.8) voice.

There's one chip that I really like, the VoicePump from the DSP Group, but they don't sell small quantities. :(

Thanks,
Alex

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2003\06\27@153839 by gtyler

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have a look at 00643b.pdf on microchip's web site.

----- Original Message -----
From: "Alex Harford" <.....alexKILLspamspam.....ALEXHARFORD.COM>
To: <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Friday, June 27, 2003 8:12 PM
Subject: [EE]: Voice codec ic's


> Hello PicListers,
>
> I'm looking for a low bandwidth voice codec solution that's easy to
interface to a microcontroller.  It's going to be for a small commercial
run, and I'm having trouble finding a reasonable solution.
>
> A single chip would be best, but I'm open to using a DSP as well.  I've
been talking to some people about licensing a DSP algorithm, but the ~25,000
US fee is a bit much.
>
> We'd like to keep our bandwidth around 8k, with toll quality (MOS ~3.8)
voice.
>
> There's one chip that I really like, the VoicePump from the DSP Group, but
they don't sell small quantities. :(
>
> Thanks,
> Alex
>
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'[PIC]: Interfacing To Voice Codec MC145484'
2004\05\08@111657 by Bob Axtell
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Anybody have experience with the Motorola MC145484
Voice Codec? Winbond has the same thing under the P/N
W8610IR. I'm trying to extract the data generated by a
PIC which then sends it via RS232 and of course input
data TO it from RS232 back into a voice pattern.

The problem is that I am having trouble understanding the relationship
between the bit clock, the master clock, and the sync signal
(that starts the transfer). I've read several explanations
and none of them seem clear enough to me to work out a
design.

What I am trying to do is to use the SPI port with SS\ in
long sync frame mode. Seems like an obvious way to do it,
but the examples never use that obvious approach.

--Bob

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             1-520-219-2363

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2004\05\08@135652 by piclist

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On Sat, 8 May 2004, Bob Axtell wrote:

> Anybody have experience with the Motorola MC145484
> Voice Codec? Winbond has the same thing under the P/N
> W8610IR.

> The problem is that I am having trouble understanding the relationship
> between the bit clock, the master clock, and the sync signal
> (that starts the transfer). I've read several explanations
> and none of them seem clear enough to me to work out a
> design.

I've worked with the Winbond part.  I agree that the datasheets aren't
at all clear, though it turns out the part is extremely trivial.
Bring frame sync high while the bit clock is low, set up or sample
data on the next eight high clocks, then bring frame sync low.  The
master clock isn't relevant to the software aspect.

I used an 18F part with the audio in a high-priority interrupt, since
you have to maintain a very precise 8 kHz on the frame sync pulse.

> What I am trying to do is to use the SPI port with SS\ in
> long sync frame mode. Seems like an obvious way to do it,
> but the examples never use that obvious approach.

I'm not sure I see how SPI would be helpful.  What would the SPI clock
be?

--
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2004\05\09@030621 by Bob Axtell

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piclist@XARGS.COM wrote:
{Quote hidden}

So you just need 8 bit clocks to receive a byte using the Frame Sync
and the data to send the byte. Do you need to provide more than 8
clocks? Can the transfer speed be almost any speed, as long as Frame
Sync is reliable?


How about the 8K period? If the master clock is slowed down in
proportion, can the chip work with 7.5K sample rate without significant
difference? I realize that there are filters, etc but if everything is
slowed down slightly all inproportion, looks like it should work almost
as well.

Thanks for the info, very much appreciated.

{Quote hidden}

Well, I would initiate SPI with the clock low, and READIN or SENDOUT the
data from DR or to DR, with the SPI clock providing the bit clock. The
ss\ will be inverted to become the Frame Suync Pulse. Wouldn't that work?


> --
> John W. Temples, III
>
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2004\05\09@131847 by piclist

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On Sun, 9 May 2004, Bob Axtell wrote:

> So you just need 8 bit clocks to receive a byte using the Frame Sync
> and the data to send the byte. Do you need to provide more than 8
> clocks?

The clocks run continuously; I assume they drive the conversions when
you're not clocking data in/out.

> Can the transfer speed be almost any speed, as long as Frame
> Sync is reliable?

The datasheet indicates the allowed clock speeds, and the transfer is
at one of those speeds.

> How about the 8K period? If the master clock is slowed down in
> proportion, can the chip work with 7.5K sample rate without significant
> difference?

I've only used it within spec.

> Well, I would initiate SPI with the clock low, and READIN or SENDOUT the
> data from DR or to DR, with the SPI clock providing the bit clock. The
> ss\ will be inverted to become the Frame Suync Pulse. Wouldn't that work?

That's not going to provide a continuous clock.  I used a 256kHz PWM
off of the PIC to provide the clocks.

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'[EE] VOIP Codecs and stuff'
2005\09\14@071733 by Russell McMahon
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OKI site.
VOIP telephone chipsets

       http://www2.okisemi.com/site/applications/VoIPPhone.html

VOIP Codec

   Intro

       http://www2.okisemi.com/site/productscatalog/telecomics/linearcodecs/Intro-9995.html

   Datasheet (1.2 MB pdf)(64 pin QFP)

A-law and ulaw CODECs, including (surprise) some in DIP.

       http://www2.okisemi.com/site/productscatalog/telecomics/pcmaulawcodecs/TelecomTables-4.html



       RM

2005\09\14@075235 by Mauricio Jancic

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What about the Microchip TCP/IP stack plus a compression codec plus a
ENC28J60 or any ethernet chip?

do you thik it would work?

Kind Regards,


Mauricio Jancic
Janso Desarrollos - Microchip Consultants Program Member
KILLspaminfoKILLspamspamjanso.com.ar
http://www.janso.com.ar
(54) 11 - 4542 - 3519

{Original Message removed}

2005\09\14@100632 by Alex Harford

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Another VOIP Codec:

http://www.dspg.com/dspg/vp141.html

2005\09\14@175931 by Peter

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On Wed, 14 Sep 2005, Mauricio Jancic wrote:

> What about the Microchip TCP/IP stack plus a compression codec plus a
> ENC28J60 or any ethernet chip?
>
> do you thik it would work?
            ^n

If you have enough bandwidth for u-law you do not need compression.
u-law needs 8 kByes/sec in each direction with *low* latency. The
simpler the circuit and the software the better. There is no reason why
it would not work. Probably in a dsPIC with a/d so a little audio
filtering can be performed. The easiest protocol to implement is
probably IAX2 (Asterisk's native protocol). TCP is not required, UDP is
enough. The other protocols seem to have been designed by commitee (H323
for sure, SIP comes close). IAX2 *works* _*NOW*_.

Peter


'[EE] Looking for a CODEC with parametric eq built '
2008\08\13@171509 by alan smith
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I've been looking in all the usual places (AKM, TI, ADI, Cirrus) for a 24bit CODEC that has built into it a digital 5 band eq circuit.  Anyone ever run across one?  Google doesn't come back with any hardware solutions, just software.


     

2008\08\17@130003 by Martin K

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alan smith wrote:
> I've been looking in all the usual places (AKM, TI, ADI, Cirrus) for a 24bit CODEC that has built into it a digital 5 band eq circuit.  Anyone ever run across one?  Google doesn't come back with any hardware solutions, just software.
>
>
>      
>  
Well at that point you're kind of specifying a DSP. If you've already
checked Cirrus, that would have been your best bet IMO.
-
Martin


'[EE] Looking For a Book Detailing the MP3 Codec'
2012\03\06@072457 by Brendan Gillatt
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Hello list,

I am looking for a book which explains the internals of the MP3 codec.

My aim is to port the ARM (classic ARM) assembly code in the libMAD
library to the Cortex-M4F core (Thumb-2). I'm fairly well accustomed
to the Thumb-2 instruction set and the libMAD code looks
straightforward enough, I'd just like a bit of a helping hand in
figuring out the bigger picture when looking through the existing
code.

I know there's the ISO/IEC 11172-3:1993 document but I find the ISO
writing style rather hard to understand without first being familiar
with the subject material. Not to mention they want £15k for the one
document!

I'd prefer a physical book but web suggestions would be okay.

Best Regards,
Brendan Gillatt

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