ISD-T360SB Datasheet, PDF (98/109 Pages) List of Unclassifed Manufacturers – VoiceDSP Digital Speech Processor with Master/Slave, Full-Duplex Speakerphone, Multiple Flash and ARAM/DRAM Support

ISD-T360SB
2—SOFTWARE
Table 2-9: TUNABLE PARAMETERS: Speakerphone
Index
Parameter Name
Description
Default
31
Acoustic Echo
Controls the bias in priority between the Send and Receive 0
Canceler (AEC):
paths.
SP_AEC_PRIORITY_BIAS If send priority-bias is preferred, the value should be greater
than zero.
For no priority bias, the value should be zero.
For priority bias for the Receive path, the value should be
negative.
Steps are 3 dB each (e.g., +3 is 9 dB bias for the Send path, –2
is 6 dB bias for the Receive path).
Legal values: –4 to 4.
32
Acoustic Echo
This parameter limits the acoustic return loss. Its value
2047
Canceler (AEC):
(SP_AEC_COUPLING_LOSS_THRESHOLD / 32767) is compared
SP_AEC_COUPLING_
LOSS_THRESHOLD
with the RMS value of S_out divided by the RMS value of R_in,
during a single-talk event. The loop gain is decreased, if
necessary, to control the TCL level.
For SP_AEC_COUPLING_LOSS_THRESHOLD = 32767 this loop is
disabled.
Legal values: 0 to 32767.
34
Acoustic Echo
Controls the speakerphone gain from the microphone to the 14000
Canceler (AEC):
line-out. The total attenuation, or gain, depends on both of
SP_AEC_LR_LEVEL
the analog gains and this value. The gain is:
K * signal
where:
K = SP_AEC_LR_LEVEL/4096.
Legal values: 0 to 16000.
36
Acoustic Echo
Specifies the positive peak-value at which the analog circuit 16000
Canceler (AEC):
of the line-out saturates. Codec analog full scale corresponds
SP_AEC_CLIP_POS
to µLAW full scale values after expansion.Assume that positive
saturation occurs at amplitudes higher than those of a sine
wave at X [dBm0]. The SP_AEC_CLIP_POS value is set as:
SP_AEC_CLIP_POS = 32636 * 10^{((X – 3.17)/20)}
Note: a sine wave with amplitude 4 * 8159 = 32636
corresponds to 3.17 dBm0.
Example:
For X = –6.2761 dBm0, the value is:
SP_AEC_CLIP_POS = 32636 * 10^{((–6.2761– 3.17)/20)} = 0.3371 *
32636 =11000;
Legal values: 0 to 32767.
37
Acoustic Echo
Specifies the negative peak value at which the analog circuit –16000
Canceler (AEC):
of the line-out saturates. Codec analog full scale corresponds
SP_AEC_CLIP_NEG
to µLAW full scale values after expansion.The value of
SP_AEC_CLIP_NEG is set as shown for SP_AEC_CLIP_POS,
above.
Legal values: –32768 to 0.
2-58
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