Specifications

AMBE-3000™ Vocoder Chip Users Manual
Version 2.8, August, 2011
In
itial Design Considerations
4.4.7 Companding Using A-Law and µ-Law
The format of the digital speech I/O is critical to designing a system with superior voice quality. It is recommended that, when
possible, 16-bit linear PCM data sampled at 8 kHz, be used for maximum voice quality. The AMBE-3000™ Vocoder Chip
supports either 16-bit linear, 8-bit A-law, or 8-bit µ-law formats. Given that a-law and law companding formats already
incorporate some compression to reduce the number of bits per sample, when choosing either format, pay particular attention to
Signal to Noise ratios and Frequency Responses of any filters that may be present on the analog front end. The a-law and
law interfaces are provided for the design engineer who is trying to fit to pre-existing conditions or is under other cost type
restraints. To enable/disable companding and select the format, use either hardware pins as described in the following tables or
the COMPAND field (ID 0x32) as part of a Control packet.
CP_ENABLE TQFP pin 8 BGA pin D1
Companding Disabled 0
Companding Enabled 1
Table 11 Companding Control
CP_SELECT TQFP pin 9 BGA pin F5
Select µ-law 0
Select a-law 1
Table 12 Companding Selection
(Subject to Change) Page 31
DVSI CONFIDENTIAL PROPRIETARY