Integrating and Evaluating Speech Algorithms

By Nitin Jain

April 16, 2007

(Integrating and Evaluating Speech Algorithms :  Page 1 of 1 )

Designing and developing an embedded system from scratch and making it stable is always a challenge. Integrating and evaluating a digital signal processing (DSP) algorithm with the system is equally tricky and can bring even the strongest programmers to their knees. Today, uncountable numbers of algorithms are embedded into various electronic systems. How does an embedded system developer know which algorithm to use for speech processing, such as that found in basic telephony systems?

The audio frequency spectrum that stretches to 40 kHz is divided in two bands. The speech components consume the lower part of spectrum, from 5 Hz to 7 kHz, with other audio components residing on the remaining higher portion, as shown in Figure 1.

Speech processing mainly involves compression-decompression, recognition, conditioning, and enhancement algorithms. Signal-processing algorithms are very dependent on system resources, such as available memory and clock capacity. As these resources add cost to systems, they're often restricted by the dproduct vendor to keep the product cost low. Basic traits, such as memory and clock consumption, are inherent parts of an algorithm's complexity. The lesser the complexity, the better the algorithm, provided it does its job efficiently.

Measuring an algorithm's complexity is the first step when evaluating an algorithm. The clocks required to run the algorithm on a specific processor determine the processing load, which is architecture dependent and varies with different processors. Memory requirements of the algorithm remain the same obviously. Most of the DSP algorithms work on a collection of samples, better known as a frame. The collection of samples to form a frame introduces an inevitable delay that is further followed by the actual processing delay. The International Telecommunication Union (ITU) standardizes the acceptable delay for each algorithm.

 Page 1 of 1