8/2/2019 G Speech

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SPEECH COMPRESSION AND DECOMPRESSION USING ADSP-2105/2115

AIM:

The objective of the project is to develop speech compression and decompression system using ADSP-2105/2115 processor. It is proposed to employ ADPCM (Adaptive Pulse Code Modulation) for Compression andDecompression.THEORY:

The analog speech signal is digitized by sampling. For maintaining the voice quality, each sample has to berepresented by 13 or 16 bits. In compression technique the digitized samples are represented by an equivalent 4 to 8 bitsamples. In decompression the compressed samples are expanded back to original sample size and converted back toanalog signals.HARDWARE:

The Hardware consists of DSP processor ADSP 2105/2115 as CPU, CODEC, EPROM RAM, Amplifier sections, Mic and speaker. The CODEC has been interfaced to ADSP processor through its serial port. The optionalhardware include PC serial port interface consisting of serial I/O port and RS-232 level converter .The TTL logic levels of serial port are converted to RS232 level using level converter, so that the system can directly communicate with thestandard serial port (com1/com2) of personal computer.

SOFTWARE:

The system software and the ADPCM algorithm for speech compression and decompression are developed inADSP-2105/2115 Assembly Language using PC. The assembly language program are compiled using ASM21 Assembler and converted to machine code which are either permanently stored in EPROM or downloaded to the ADSP systemthrough PC serial interface.FUNCTIONING:

The system is operated through the reset and interrupt switch. Once the system is resetted it will be ready toaccept the speech signals through the Mic and CODEC. The analog speech signals are amplified by the pre-amplifier andfed to the CODEC for analog to digital conversion .The CODEC transmits the digitized signal to the ADSP 2105/2115

processor, which then compress the speech data using the ADPCM techniques and store in RAM. When the processor isinterrupted, it reads the compressed data from RAM expands the data and send the data to CODEC. The CODEC convertsthe digital data to analog signal, which is amplified and output through the speaker.APPLICATION:

The speech compression and decompression techniques are implemented in the applications like1. Cellular phones

2. Voice mail transmission3.Speech recognition system4.Voice storage5.IVRS(Interactive Voice Response System)

BLOCK DIAGRAM OF SPEECH COMPRESSION AND DECOMPRESSION USING ADSP-2105/2115

RS-232

LEVELCONVERTER

PC

RAM

OPTIONAL HARDWARE

LATCH

BUFFER

RS-232BUS

S Y S T E M

B U S

EPROM

MIC

AMPLIFIER CODEC

ADSP

2105/2115

RESET

INTERRUPT

CLOCK

SERIALPORT

LPORT

SPEAKER