Lossless compression of audio is being popular during the last few decades due to rapid and advanced technology of high quality sound production improved. Lossless compression is a class of compression algorithms that allows the original data to be reconstructed perfectly from the compressed one while for lossy compression, it permits reconstruction only approximate to the original one and it is commonly allows for improved compression rates and smaller in file size.
Speech coding can be defined as the act of transforming the speech signal to a more compact form in smaller memory. The access to unlimited bandwidth is impossible. Thus, code and compressing of speech signal are needed. Since speech compression required in long-distance communication, high-quality speech storage, and message encryption, many users need to share the same frequency bandwidth in digital cellular technology. The solution is by utilizing speech compression makes it possible for more users to share the available system. Speech coding is a lossy type of coding. The output signal does not exactly sound like the input. Audio coding tries to code the audio in a perceptually lossless way. The sound at the output is the similar as the input even though the input and output signals are not mathematically equivalent. This type of coding is commonly used for audio storage, broadcasting as well as Internet streaming . There are several techniques of speech coding for example Linear Predictive Coding (LPC), waveform coding and subband coding (Abdul et.al ,2003).
According to Gersho (1994), speech coding can be divided into two categories which are waveform coders and vocoders. The term vocoder is combination from voice and coder term. The waveform coder provides the approximate of original sound as data is transmitted from encoder to decoder. Then, it will specify a representation of the original speech in term of amplitude versus time. The vocoders are the vice versa of coder which means that it does not produce the approximate original waveform. It provides the new and reconstruct the waveform not approximate to original one but the sound is quite similar. Braudbery explained in his study about four main attributes of LPC vecoder including bit rate, delay,complexity and quality.
Basic Operations In Lossless Compression Algoritms
Figure 1 The basic operations in most lossless compression algoritms
The framing operations are to provide for edibility which is the essential property for most of applications dealing with digital audio (Hans & Schafer,2001). On the encoder side, the audio samples are buffered and divide the digital audio signal into independent frames with equal time duration. This is due to the sheer volume of data prohibits repetitive decompression of entire signal preceding region to be edited. Each block has been analyzed, so that the optimal predictor can be determined. As a result, different predictor will be used to process different blocks or frames...