Digital Voice Systems AMBE-3000 Specifications download pdf (Page 89)

AMBE-3000F™ Vocoder Chip Users Manual

Version 3.4, April, 2014

Dat

a and Configuration Packets

6.7 Input Speech Packet Format (Packet Type 0x02)

A speech packet uses the general packet format where the PACKET TYPE is equal to 0x02. For every speech packet input

(packet type 0x02) to the AMBE-3000F™ Vocoder chip, the chip will output channel packet (packet type 0x01). Speech

packets are used only when the AMBE-3000F™ Vocoder Chip is operating in packet mode.

6.7.1 Speech Packet Fields

The speech packet supports the following packet fields:

Speech Packet - Fields

Field Name Field Identifier Data Length Description

PKT_CHANNEL0 0x40 1 byte The vocoder for subsequent fields

SPEECHD 0x00 Variable bytes The speech data to be encoded for current vocoder

CMODE 0x02 2 bytes cmode flags for current vocoder’s encoder

TONE 0x08 2 bytes Force current encoder to generate tone frames

Table 98 Speech Packet Fields

PKTCHANNEL_ID field (2 bytes) indicates the vocoder the control is intended for. It is the same as described in the Table

33 P

KT_CHANNEL(0) Field Format

A SPEECHD field (variable number of bytes) contains the speech data to be encoded for the current channel or the decoded

speech data for the current channel.

When using 16 bit linear PCM Raw Speech data to be input to the encoder or output from the decoder there will be 16 bits per

sample, this means at 160 samples there are 320 bytes of data. When using companded data (a-law or µ-law there are 8 bits of

data per sample, this results in 160 bytes of data in 160 samples. The speech is denoted as Speech[0] thru Speech[2*{samples}

-1].Speech[0] is the MS byte of the first sample. Speech[1] is the LS byte of the first sample. Speech[2*{samples}-2] is the

MS byte of the last sample. Speech[2*{samples}-1] is the LS byte of the last sample.

SPEECHD Field - Packet Format

Field Identifier Number of Samples Data

1 Byte 1 Byte Variable Number of Samples

0x00 156 <= {samples} <= 164 Speech[0] … Speech[2*{samples}-1]

Table 99 SPEECHD Field Format

CMODE fields (3 bytes total) may be used to change the mode of the encoder on a frame-by-frame basis. The CMODE field

will enable/disable advanced features of the encoder when sent as part of a speech packet.

CMODE will overwrite any values set by the PKT_ECMODE field as well as, the state as set by the corresponding hardware

configuration pin. In order not to inadvertently turn off or on features that were originally set by ECMODE_IN or set via

hardware configuration pins to be sure that CMODE is or'd with the correct value of the desired ECMODE_IN. Except for

Tone Generation, typically, once these values are set they do not change. So it is not necessary to send CMODE fields on a

frame-by-frame basis.

For example, to enable tone detection, DTX and noise suppression, CMODE data value would be 0x1840. In order to generate

a tone and retaining all of the other settings then CMODE data value would be 0x5840.

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Digital Voice Systems AMBE-3000 Specifications Page 89