Thursday, 13 August 2015

Encoder Description



This coder is intended to work with a computerized sign acquired by first performing phone data transmission sifting  (Suggestion G.712) of the simple data, then inspecting at 8000 Hz and after that changing over to 16-bit straight PCM for the info to the encoder. The yield of the decoder ought to be changed over back to simple by comparative means. Other information/yield qualities, for example, those predetermined by Recommendation G.711 for 64 kbit/s PCM information, ought to be changed over to 16-bit straight PCM before encoding or from 16-bit direct PCM to the proper configuration subsequent to unraveling. The bit stream from the encoder to the decoder is characterized inside of this Recommendation. The coder is in light of the standards of straight forecast investigation by-amalgamation coding and endeavors to minimize a perceptually weighted mistake signal. The encoder works on squares (edges) of 240 specimens each. That is equivalent to 30 msec at a 8 kHz examining rate. Every square is first high pass sifted to uproot the DC segment and after that isolated into four sub casings of 60 specimens each. For each sub outline, a tenth request Linear Prediction Coder (LPC) channel is processed utilizing the natural data signal. The LPC channel for the last sub casing is quantized utilizing a Predictive Split Vector Quantize. (PSVQ). The quantized LPC coefficients are utilized to develop the transient perceptual weighting channel, which is utilized to channel the whole edge and to acquire the perceptually weighted discourse signal. For each two sub frames (120 examples), the open circle pitch period, LOL, is figured utilizing the weighted discourse signal. This pitch estimation is performed on squares of 120 examples. The contribute period is looked the extent from 18 to 142 examples. Starting here the discourse is prepared on a 60 examples for each sub frame premise. Utilizing the assessed pitch period processed beforehand, a consonant clamor forming channel is built. The mix of the LPC union channel, the formant perceptual weighting channel, and the symphonious clamor molding channel is utilized to make an motivation reaction. The motivation reaction is then utilized for further reckonings. Utilizing the pitch period estimation, LOL, and the motivation reaction, a shut circle pitch indicator is figured. A fifth request pitch indicator is utilized. The pitch period is figured as a little differential quality around the open circle pitch gauge. The commitment of the pitch indicator is then subtracted from the introductory target vector. Both the pitch period and the differential quality are transmitted to the decoder. At long last the non-occasional part of the excitation is approximated. For the high bit rate, Multi-beat Maximum Probability Quantization (MP-MLQ) excitation is utilized, and for the low bit rate, a logarithmic code-excitation (ACELP) is utilized.

No comments: