The PIC24/dsPIC® Digital Signal Controller (DSC) G.711 Speech Encoding/Decoding Library performs toll-quality voice compression and voice decompression. The library is an implementation of the ITU-T G.711 standard on the dsPIC DSC. The encoding algorithm used is either A-law or μ-law companding (user-selectable), and features a 2:1 compression ratio. G.711 uses minimal computational resources, and a well-defined API makes it easy to integrate with the application.
The G.711 library can be used for both half-duplex and full-duplex systems. However, due to its high output data rate, it is most suitable for full-duplex communications applications that do not need to store the encoded speech for subsequent playback. Some target applications include:
A flexible analog interface gives your design several options to consider. The speech encoder samples speech at 8 kHz using either an external codec or the on-chip 12-bit Analog-to-Digital Converter (ADC). The speech decoder plays decoded speech through an external codec or the on-chip Pulse Width Modulator (PWM). Storing compressed speech for playback requires 8 KB of memory for each second of speech.
A PC-based Speech Encoder Utility program creates encoded speech files for playback. Encoded speech files are made from either a PC microphone or existing WAV file. Once the encoded speech files are created, they are added to an MPLAB® IDE project, just like a regular source file, and built into the application.
Resource Requirements
Please refer to user’s guide for resource requirements
Key features of the G.711 Speech Encoding/Decoding Library:
• Fixed 8 kHz input sample rate
• Fixed 64 kbps output data rate
• PESQ-based Mean Opinion Score (MOS): 4.3 to 4.5 (out of 5.0)
• A-law or μ-law based coding
• Two analog input interfaces — codec or on-chip ADC
• Two analog output interfaces — codec or on-chip PWM
• Playback-only applications benefit from the Speech Encoder Utility. Encoded files can be created from the desktop using a PC microphone or WAV file.
• Storing compressed speech requires 8 KB of memory per second of speech
• FREE library
• Full compliance with Microchip's MPLAB® C30 C compiler language tools
• PIC24/dsPIC DSC G.711 Speech Encoding/Decoding Library User's Guide assists in using the library
• Designed to run on dsPICDEMTM 1.1 General Purpose Development Board
Devices Supported
