TRANSKODING PULSE CODE MODULATION 64 KB/S DAN LOW DELAY CODE EXCITED LINEAR PREDICTION 16 KB/S

• Main Author: Budi Setiawan , Florentinus
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/4677
• Institution: Institut Teknologi Bandung

<b>Abstract :</br><p align=\"justify\">The high quality speech which is transmitted by speech signal in telephone bandwidth need high rate of bits. Speech signal with quite similar quality with one can be transmitted with lower rate of bits.<p align=\"justify\"> <br /> At rate 16 kbps CCITT recommended a general purpose standart. CCITT recommended that algorithm delay can not over than 5 ms and the aim is less than 2 ms.<p align=\"justify\"> <br /> Data rate at 64 kb/s in PCM format can be converted to the lower rate 16 kb/s in LD-CELP format. Converting rate to the lower rate needs a transcoder which can convert from PCM 64 kbps to LDCELP 16 kbps, viceversa. Converting format will save 75% of bit rates, but it makes degradation of perception quality. In this thesis, the analysis would make for both encoder and decoder, so that the high quality synthetics speech can be heard similar as the original input speech in encoder.<p align=\"justify\"> <br /> LD-CELP is a predictive coder, which is consist of backward adaptive linear backward with high order, backward adaptive vector quantisation gain, searching of excitation CELP codebook use analysis by synthesis method and adaptive postfilter. Coding delay is reduced by use backward adaptive prediction and small size of vector quantisation., only five sample.. These requirement is fullfilled by make some calculation and algorithms so that the quality will increase.<p align=\"justify\"> <br /> In this thesis, input signal is PCM 64 kb/s signal while the output is LD-CELP 16 kb/s format (encoding). On the inverse transformation (decoding), input signal is LD-CELP 16 kb/s format while the output is PCM 64 kb/s format. Delay time will be reached is less than 5 millisecond for encoding maupun dekoding. The simulation programs are arranged with Borland C++ compiler version 4.0.