general more complex. They are base

general more complex. They are based on using priori knowledge about the signal to be coded. and for this reason, they are, in general, signal specific.

7.2 Characteristics of Speech Signals
Speech waveforms have a number of useful properties that can be exploited when designing efficient coders [FlaT9]. Some of the properties that are most often utilized in coder design include the nonuniform probability distribution of speech amplitude. the nonzero autocorrelation between successive speech samples, the nonflat nature of the speech spectra, the existence of voiced and unvoiced segments in speech, and the qussiperiodicity of voiced speech signals.The most basic property of speech waveforms that is exploited by all speech coders is that they are bandliinited. A finite bandwidth means that it can be time diecretized (sampled) at n finite rate and reconstructed oornpletely from its samples, provided that the sampling frequency is greater than twice the highest frequency component in the low pass signal. While the band lini.ited property of speech signals makes sampling possible, the aforementioned properties allow quantization, the other most important process in speech coding, to be performed with greater efficiency.

Probability Density Function (pdf)—- The nonuniform probability density function of speech amplitudes is perhaps the neat most exploited property of speech. The pdf of a speech signal is in general characterized by a very high probability of near-zero amplitudes. a significant probability of very high amplitudes. and a monotonically decreasing function of amplitudes between these extremes. The exact distribution. however, depends on the input bandwidth and recording conditions. The two-sided exponential (Laplacian) function given in equation (7.1) provides a good approximation to the long-term pdf of telephone quality speech signals [JayS4].

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umum lebih kompleks. Mereka didasarkan pada menggunakan priori pengetahuan tentang sinyal untuk dikodekan. dan untuk alasan ini, mereka adalah, dalam umum, sinyal specific.7.2 Karakteristik pidato sinyalBentuk gelombang pidato memiliki jumlah properti berguna yang dapat dimanfaatkan ketika merancang efisien coders [FlaT9]. Beberapa properti yang paling sering digunakan dalam desain coder meliputi distribusi probabilitas nonuniform pidato amplitudo. Autokorelasi bukan nol antara sampel pidato berturut-turut, sifat nonflat spektrum pidato, keberadaan segmen bersuara dan nirsuara dalam pidato, dan qussiperiodicity disuarakan pidato sinyal.Properti paling dasar dari bentuk gelombang pidato yang dimanfaatkan oleh semua pidato coders adalah bahwa mereka bandliinited. Bandwidth finite yang berarti bahwa hal itu dapat waktu diecretized (sampel) pada tingkat n finite dan oornpletely direkonstruksi dari sampel yang, asalkan frekuensi sampling lebih dari dua kali komponen frekuensi tertinggi dalam sinyal lulus rendah. Sementara band lini.ited properti pidato sinyal memungkinkan pengambilan sampel, sifat-sifat tersebut memungkinkan kuantisasi, proses yang paling penting lain dalam pidato pengkodean, akan dilakukan dengan lebih besar efficiency.Fungsi kepekatan probabilitas (pdf) —-nonuniform probabilitas kepadatan fungsi pidato amplitudo adalah mungkin properti paling dieksploitasi rapi pidato. File pdf sinyal pidato pada umumnya ditandai dengan probabilitas sangat tinggi dekat-nol amplitudo. probabilitas significant amplitudo sangat tinggi. dan monotonically penurunan fungsi amplitudo antara ekstrem. Distribusi yang tepat. Namun, tergantung pada masukan bandwidth dan kondisi rekaman. Dua sisi (Laplacian) fungsi eksponensial diberikan dalam persamaan (7.1) menyediakan perkiraannya ke pdf jangka panjang telepon kualitas pidato sinyal [JayS4].