Home
Modems
Telephony
Audio
Utilities
Consultancy
Glossary
Index
Contact us

Hi-Fi Band Audio Coder TMS320C5000 DSP Code

Description: this proprietary audio coder operates a sample rate of 32kHz on an audio bandwidth of 50Hz - 15kHz. The compression is to 96, 112, or 128kb/s, selectable at the main routine interface. The input-output samples are 16-bit as is the coder dynamic range. The algorithm uses Adaptive Differential Pulse Code Modulation (ADPCM) in a sub-band configuration. As such it is a waveform coder and so transcodes many different types of audio signals. Single voice, multiple voices, and music all sound clear and natural through headphones or loudspeakers, though not quite with "CD" quality because of the coder limitations. Hence the coder is termed "Hi-Fi Band" as opposed to proper hi-fi for CD quality which has a wider audio bandwidth (44.1kHz sample rate) and better dynamic range (24 bits).
         The encoder and decoder routines are operated as separate items with individual main subroutine calls. With the assembler interface, each should be called every 8kHz. The encoder requires 4 successive input samples, and generates a single 12-/14-/16-bit ADPCM code per call depending on the data rate set as respectively 96/112/128kb/s. The decoder takes the ADPCM code as input and generates 4 successive output samples.
         A separate subroutine call is made for initialisation of encoder or decoder. The code routine calls are re-entrant to allow multi-channel operation, the memory block associated with each channel being pointer-addressed. A C-callable wrapper file can also be provided, allowing individual channels to be called from C for processing of multiple sample/code blocks. A comprehensive user's guide is provided with the code.

Processor Load:

- #figures for assembler interfaces with TMS320C54x operation

Availability: NOW - sale is under licence - integration support offered