AC97 CODEC Library functions

[bimbla]

The general purpose family of dsPIC have a built-in AC97 CODEC.
It would be nice to have built-in library functions to access the same.

Thanks and regards.

bimbla.

[LGR]

They don't have a built-in codec, they have an interface for the codec. It's a syncronous protocol, similar to SPI. You can chose your codec to match your needs. Bob Lawrence already asked for GEQ. I think a lot of people are going to want goodies, particularly audio goodies. My only regret is that the dsPIC doesn't have enought RAM do decode OGG. MP3 might be a possibility, if there is an integer GNU decoder out there somewhere....

[Bob Lawrence]

LGR,

I don't know what GEQ is. Actually, I was asking for a programming example
to create a 31 band equalizer using IIR filters. Once they get the libraries completed it should be no problem.

[LGR]

I don't know what GEQ is. ...... create a 31 band equalizer using IIR filters..

GEQ: Graphic equalizer.

One thing about a 31 band EQ - how do you intend to adjust it? That's a lot of pots to connect to analog inputs, and I don't think that the 80-pin chips have that many analog inputs. If you haven't already, you should check out SuSE linux. It comes with a ton of audio/MIDI toys and can do what you are talking about on an old P-233 box. Probably cheaper than trying to set up a dsPIC.

If you need something more compact than a computer, search for "single board computer" on ebay, and you'll get an number of ISA sized cards which are complete motherboards for $10-25 each. I built a complete computer with HDD and CDrom in a standard mailbox! Somebody in Montreal was selling lots of 10. Just add power supply, disk and sound card.

[SmartDrive]

Personally, when I get round to doing a 31 band GEQ I shall probably do it using two digital pots and a graphic LCD. The first one acts as a band select and the second is the adjust up/down. I've used many geq's that work on that form of principle.

Another method is to use 31 pots and say 8 analogue inputs and scan them in a matix like a keypad function, but that's alot of work to get the front panel right!

[Bob Lawrence]

LGR,

Ok, that G word that doesn't have a real meaning for a EQ.

Maybe 31 bands is a bit much but from the Microchip design contest this guy had 2, 12 band EQ's

"The $15,000 USD first-place prize went to Wetzel's "Stereo Audio System" entry. This top design is for an audio processing system, which takes advantage of the dsPIC30F's buffered on-chip peripherals to minimize interrupt service time and maximize overall performance. As a result, Wetzel was able to include a dual 12-band graphic equalizer using independent IIR filters with performance left over for dual audio-amplitude compressors that are used to control dynamic volume range. His design also includes a real-time VU meter display using some of the dsPIC30F's unique instructions to facilitate the fast calculation of decibels on the LCD display. These features are particularly useful for environments where the range of audio volume should not vary to levels that are too quiet or too loud, such as an elevator."

=============================================
More info on the contest:
http://biz.yahoo.com/bw/041210/105385_1.html

[bimbla]

Sorry my mistake.
I ment built-in AC97 CODEC interface!

What we need as an audio tool is implementation of a bi-quad filter.
A library command to input the value for its parameters (A0,A1,A2,B1,B2)

We can then configure this as LPF,HPF, Peaking filter (for GEq), Shelving filter (for Bass and Treble)

Another block I wish is the Compressor/ Expander block.

Actually give me HPF, LPF, GEq., Compressor/ Expander, adder, subtract., delay and I will give you a Surround Decoder with equalizer.

(Ref. AD1954 and TAS3002)

bimbla.

[LGR]

Also, once you are done with the equalization, you can do speaker crossover. Its probably cheaper, and better performance to have seperate amplifiers for each element (class D for the woofer), like they do it in car systems.