Group Members :
Joshita Reddy
Nayanika Reddy
Nirmit Maniar
Implementation
- Practical implementation of PCM makes use of other processes which are carried out in the order:
- Sampling
- Quantization and
- Encoding
Linear Pulse code modulation
Pulse code modulation
- It is a method used to digitally represent sampled analog signals
- In a PCM stream, the amplitude of the analog signal is sampled regularly at uniform intervals
- Each sample is quantized to the nearest value within a range of digital steps
Applications of PCM
- Lossless encoding of audio data in the compact disc(audio cd)
- HDMI: Audio/video connetor interface for transmitting uncompressed digital data
- DVD and Blu-ray standards
Modulation
- In the diagram following, a sine-wave is sampled and quantized for PCM.
- The vertical lines are the sampling intervals
CODE:
clc;
clear all;
close all;
t=0:0.01:5;
x=2*sinc(2*pi*t);
figure;
plot(x);
hold all;
e=uencode(x,3);
d=udecode(e,3);
plot(d);
c=compand(x,255,2,’mu/compressor’);
e1=uencode(c,3);
d1=udecode(e1,3);
ex=compand(d1,255,2,’mu/expander’);
plot(ex);
xlabel(‘time’);
ylabel(‘magnitude’);
title(‘pulse code modulation of sinc function’);
Pulse code modulation and it's applications
Why PCM?
- The stream of pulses and non pulse streams of 1's and 0's are not easily effected by interference and noise
- Even in the presence of noise,the presence or absence of a pulse can be easily determined
- Also digital signals are easy to process and cheaper to implement
Clarity acc to number of bits/sample
Limitations
- There are 2 sources of impairment implicit in any PCM system
- Choosing the discrete value near the analog signal(quantization error)
- There is no measurement of signal between the samples;due to the sampling theorem this results in any frequency above sampling frequency being distorted or lost completely