چکیده:
This paper presents a full duplex, real time implementation ol ITU- T Ci.723 , 1 [7,S] speech coder using the TMS320C5402 DSP chip which is based on a 16 bit fixed-point architecture. An optimization metho‹) is proposed in order to reduce the total necessary cycle time consumed in real-time irnplcmcntation. The Multi-Pulsc Maximum Likelihood Quantization (MP- MLQ) excitation scarch block which is the most computation-intensive block in the coder is restructured to rcduce the algorithinic redundancy. In addition, cfficient filtering methods and mcmory management are used for further tiptirnization. The bit-cxact verification with the ITU test vectors and performance evaluation aspects are also discusscd in this paper.
خلاصه ماشینی:
R. of Iran This paper presents a full duplex, real time implementation ol ITU- T Ci. 723 , 1 [7,S] speech coder using the TMS320C5402 DSP chip which is based on a 16 bit fixed-point architecture.
I proposed by ITU -T, is a low-bit-rate speech coder for multimedia serviccs.
It is based on the CELP (Code Excited Lincar Prediction) [ 13] which is an analysis-by-synthesis coder showing a good quality of speech with a bit rate range between 4 and 16 Kbits/sec.
These pitches are used as reference values for finding thc optimal lag of harmonic noise shaping filter and the closed- loop p itch of the adaptive codebook.
As shown in the Figure (3), the fact is that the M P-M LQ codebook search procedure takes up above 55*/o computational complexity in the encoding of thc G.
1 C-code was found; one in MP-MLQ search, [1] the others in the decoding of adaptive codcbook, and memory shift operations of FIR and 11 R filtcrs.
The local maximum pints of d(t) would be located, and then, the M indices that own the first M largest absolute valuc of cross-correlation and concurrently satisfy this equation are selectcd: In discrete domain, a simple method to find t(View the image of this page) he pre-selection position is described as: Slep 1 : find thc index for (d(n)>—0)&&(d[n]-d[n- 1 ]>=0)&&((d[n] -d[n* l ])?=-()) or (d(n) and record the corresponding absolutc value of cross-correlation concurrent ly.
V. “Three New Speech Coders from the ITU Covers a Range of Applications,” IEEE C‹›mmunication Magazine, September 1997.