Copyright © Philip M. Parker, INSEAD. Terms of Use.
| Domain | Definition |
Computing | A narrowband analog-to-digital conversion technique employing a one-level or multi-level sampling system in which the value of the signal at each sample time is predicted to be a particular linear function of the past values of the quantized signal. Source: European Union. (references) |
| Form of parametric coding which allows high speech compression; as the formant frequencies tend to change slowly, current samples are predicted from weighted linear predictions of previous samples. Source: European Union. (references) | |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
LPC starts with the assumption that a speech signal is produced by a buzzer at the end of a tube. The glottis (the space between the vocal cords) produces the buzz, which is characterized by its intensity (loudness) and frequency (pitch). The vocal tract (the throat and mouth) forms the tube, which is characterized by its resonances, which are called formants. LPC analyzes the speech signal by estimating the formants, removing their effects from the speech signal, and estimating the intensity and frequency of the remaining buzz. The process of removing the formants is called inverse filtering, and the remaining signal is called the residue.
The numbers which describe the formants and the residue can be stored or transmitted somewhere else. LPC synthesizes the speech signal by reversing the process: use the residue to create a source signal, use the formants to create a filter (which represents the tube), and run the source through the filter, resulting in speech.
Because speech signals vary with time, this process is done on short chunks of the speech signal, which are called frames; generally 30 to 50 frames per second give intelligible speech with good compression.
LPC is frequently used for transmitting spectral envelope information, and as such it has to be tolerant for transmission errors. Transmission of the filter coefficients directly (see linear prediction for definition of coefficients) is undesirable, since they are very sensitve to errors. In other words, a very small error can distort the whole spectrum, or worse, a small error might make the precition filter unstable.
There are more advanced representations such as log area ratios (LAR), line sprectrum pairs (LSP) decomposition and reflection coefficients. Of these, especially LSP decomposition has gained popularity, since it ensures stability of the predictior, and spectral errors are local for small coefficient deviations.
How it works
LPC coefficient representations
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Linear predictive coding."
| The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com. |
| Expression | Frequency per Day |
linear predictive coding | 2 |
| Source: compiled by the editor from various references; see credits. | |
| Language | Translations for "LINEAR PREDICTIVE CODING"; alternative meanings/domain in parentheses. | ||||||||||||||||||||||
Danish | LPC, kodning ved lineær forudsigelse. (various references) | ||||||||||||||||||||||
Dutch | LPC, lineair voorspellende codering, codering volgens lineaire predictie. (various references) | ||||||||||||||||||||||
Finnish | LPC-koodaus, lineaarinen ennakoiva koodaus. (various references) | ||||||||||||||||||||||
French | LPC, codage prédictif linéaire, codage par prédiction linéaire. (various references) | ||||||||||||||||||||||
German | Codierung mit linearer Vorhersage. (various references) | ||||||||||||||||||||||
Greek | γραμμική προγνωστική κωδικοποίηση, ευθύγραμμη προβλεπόμενη κωδικοποίηση. (various references) | ||||||||||||||||||||||
Italian | LPC, codifica lineare a predizione, codice predittivo lineare. (various references) | ||||||||||||||||||||||
Pig Latin | inearlay edictivepray odingcay codificação preditiva linear, codificação linear preditiva. (various references) LPC, codificación predictiva lineal, codificación por predicción lineal, codificación lineal predecible. (various references) linjär prediktiv kodning. (various references) | ||||||||||||||||||||||
Copyright © Philip M. Parker, INSEAD. Terms of Use.
