CVSD - Continuously Variable Slope Delta Modulation

ADT CVSD Military Standard vocoder C64x, C55x

DESCRIPTION

Adaptive Digital's CVSD is a 1 bit/ sample vocoder. It supports 8khz to 16khz input sampling and yields 8kbit – 16 kbit/sec compressed speech. The CVSD codec is designed for use in military communication systems.

Continuously Variable Slope Delta (CVSD) Modulation: As the name implies is Delta modulation (DM) with variable step size. A method by which a voice signal is digitized for transmission, and then changed back to an analogue voice signal during reception. The size of the steps of the approximated signal is progressively increased or decreased as required to make the approximated signal closely match the input analog wave.

APPLICATIONS

Wideband encryption

FEATURES

Functions are C-callable.
Multi-channel capable
CVSD encodes at 1 bit per sample, so that audio sampled at 16kHz is encoded at 16 kbps

Sampling Rate: 8 kHz Coding Rate = 8000 bps
Sampling Rate: 12khz Coding Rate = 12000 bps
Sampling Rate: 16khz Coding Rate = 16000 bps

AVAILABILITY

ADT CVSD is available on the TMS320™ DSP Family

C64x/C64x+™ & C55x™ DSP Generations

SPECIFICATIONS

C55x
SPECIFICATIONS:

C55x - MIPs (Peak)
	8000 hz/8000 bps		12000 hz/12000 bps		16000 hz/ 16000 bps
Software	Encode	Decode	Encode	Decode	Encode	Decode
CVSD	0.4	0.4	0.6	0.6	0.8	0.82

C64x / C64x+

C64x - MIPs (Peak)
	8000 hz/8000 bps		12000 hz/12000 bps		16000 hz/ 16000 bps
Software	Encode	Decode	Encode	Decode	Encode	Decode
CVSD	0.2	0.2	0.3	0.3	0.4	0.41

All Memory usage is given in bytes.

Memory
Software	Program Memory	Tables	Data Memory	Channel Memory
Encoder / Decoder	512	0	0	14

FUNCTION

CVSD_ADT_reset (. . .)       Initializes the CVSD
CVSD_ADT_encode (. . .)    Executes the CVSD encoder
CVSD_ADT_decode (. . .)    Executes the CVSD decoder