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…. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Dec 21, 2015

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Page 1: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Page 2: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

* * WirelessWireless** Audio Effects Audio Effects ProcessorProcessor

Lohith KiniRahul Shroff

Spyros Zoumpoulis

April 30th, 20076.111 Project Presentation

Page 3: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Our Model: AirTunes®

• Audio input from source

• Compressed • Wirelessly transmitted• Decompressed• Equalizer & Audio

Effects

Page 4: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Top Level Block DiagramTop Level Block Diagram

AC97 Controller

AC97Codec

Decompression

IMDCTSRAM

Compression

MDCT

SRAM

FSM

FSM

Transmission

Reception

FFT

IFFT

Equalizer

Equalization

Page 5: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Compression of AudioCompression of Audio

• MP3, MPEG-4, AACMP3, MPEG-4, AAC– ModifiedModified Discrete Cosine Transform Discrete Cosine Transform

• LappedLapped : Map : Map 2N2N discrete points into discrete points into NN discrete discrete pointspoints

MDCT

Page 6: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

AC97

ac97_bit_clock(global)

ac97_sdata_out

ac97_sdata_inac97_synch

AC97 Controller

WR Data

18

FIFO

Compression

CLKRD Data_Out

DA

DataND

CLK

RESET

RFDData_Out RDY

1D MDCT

18

AC97 FSM

CompressionFSM

WIRELESS MEMORY

WEaddress

Data_Out

18

18

16-pt.

8-pt.

8-pt.

16-pt.

10

Page 7: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Wireless CC2420DBK RF Wireless CC2420DBK RF Transceiver Transceiver

• CC2420 radioCC2420 radio• 2.4 GHz frequency band 2.4 GHz frequency band • Atmel Atmega128L AVR microcontrollerAtmel Atmega128L AVR microcontroller• 2x32 kBytes external RAM2x32 kBytes external RAM• PCB antennaPCB antenna• Joystick, buttons, LEDs (visual user application interface)Joystick, buttons, LEDs (visual user application interface)

Page 8: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Wireless Big PictureWireless Big Picture

Packet TransmitterPacket Transmitter

Packet ReceiverPacket Receiver

Encoder Encoder (FEC)(FEC)

BlockBlockMemoryMemory(wireless)(wireless)

TX Control UnitTX Control Unit

Decoder Decoder (FEC)(FEC)

RX Control UnitRX Control Unit

BlockBlockMemoryMemory(wireless)(wireless)

FPGAFPGA

FPGAFPGA

Page 9: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Wireless Transmission AlgorithmWireless Transmission Algorithm

• Error Correction AlgorithmError Correction Algorithm– Forward Error Correction (FEC)Forward Error Correction (FEC)

• sender adds redundant data to its messagessender adds redundant data to its messages• allows receiver to detect errorsallows receiver to detect errors

• Reed Solomon CodeReed Solomon Code– Key idea:Key idea:

• data is encoded as a polynomialdata is encoded as a polynomial• any any kk distinct points distinct points uniquelyuniquely determine a polynomial of degree at most determine a polynomial of degree at most kk-1-1

– Polynomial is then “encoded” by its evaluation at various points, and these Polynomial is then “encoded” by its evaluation at various points, and these values are what is actually sentvalues are what is actually sent

– Transmission: some of these values may become corrupted Transmission: some of these values may become corrupted – More than More than kk points are actually sent points are actually sent– Receiver decodes the original dataReceiver decodes the original data– Total number of m-bit symbols in the encoded block is Total number of m-bit symbols in the encoded block is n = 2n = 2mm - 1 - 1

• Example: m = 8, Code Rate 223/255 Example: m = 8, Code Rate 223/255 – (In each block 223 symbols are formed from the encoder input and 32 parity (In each block 223 symbols are formed from the encoder input and 32 parity

symbols are added.) symbols are added.) – Capable of correcting up to 16 symbols per blockCapable of correcting up to 16 symbols per block

Page 10: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Equalization

• Use FFT to convert audio signal into frequency spectrum

• Add desired effects as required by the user

• Take IFFT of resulting signal

• Transmit processed audio to AC-97 output line

Page 11: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

DecompressionDecompressionMemoryMemory

1024-pt.1024-pt.FFTFFT

BucketizerBucketizer

EqualizerEqualizer

MultiplierMultiplierModuleModuleIFFTIFFTLPFLPF

AC-97AC-97

18

FFT_real

FFT_img

FFT_index

18

18

10

Mult_re

Mult_im

ifft_enable

18

18

real_inv

8

to_ac97_data

Audio Effects: The BIG PictureAudio Effects: The BIG Picture

Page 12: …. * Wireless * Audio Effects Processor Lohith Kini Rahul Shroff Spyros Zoumpoulis April 30 th, 2007 6.111 Project Presentation.

Questions?Questions?