A touch-screen controlled 'Linear Predictive Synthesizer' for accessibility applications
Benjamin W. D. Jordan · University of Southern Queensland ePrints (University of Southern Queensland) · 2009
Numerous voice compression methods are available today for communications over low bandwidth channels. Worthy of note in particular are Linear Predictive Coding (LPC), Mixed Excitation LPC (MELP), and Code Excited LPC (CELP). The channel in these coding schemes is typically a digital transmission line or radio link, such as in cellular telephone communications, but may be other media such as files on a computer hard disk. Linear Predictive Coding is explored in some detail as a basis for creating a new speech synthesizer that does not convert text to speech (TTS), but rather uses a touch-screen Thin Film Transistor (TFT) panel as user input to create and control voice-like audio sound synthesis. Research has been carried out to conceptually try different methods for mapping TFT touch panel input (or any 2-dimensional input) to LPC synthesis coefficient vectors for artificial speech reproduction. To achieve this, various LPC coefficient quantization algorithms have been explored and evaluated using Octave v.3 scripts, resulting in selection and comparison in the final hardware and software implementation. The hardware and software development platform used for the final implementation is the Altium Nanoboard 3000 Xilinx Edition, along with the Altium Designer EDA package. The Nanoboard 3000 was chosen as it provided a convenient FPGA platform and all the necessary IP, IP Synthesis, and C compilers needed to prototype the design and perform further research