AT2004 Datasheet, PDF (11/25 Pages) List of Unclassifed Manufacturers – 4 Channels ADPCM Processor with Echo Cancellation and Conferencing

AT2004
4 Channels ADPCM Processor with Echo Cancellation and Conferencing
Stepsize2/Stepsize1 Description
0
0 Gain is +3dB of normal case
0
1 Normal case (default setting)
1
0 Gain is -3dB of normal case
1
1 Gain is -6 dB of normal case
Default: 01 for normal case.
Stepsize control the adaptation speed of adaptive filter. Default setting is the empirically chosen optimal setting. Reduce the stepsize will
make echo canceller more stable (robust), however, it will take longer time to converge. Increase the stepsize will have opposite effect.
Comfort_noise2/Comfort_noise1 Description
0
0
No comfort noise generation
0
1
Pseudo random noise
1
0
Noise generated by clipping
1
1
Not defined
Default: 10 for noise generated by clipping.
AT2004 supports two comfort noise generation schemes. One is by generating pseudo random noise with energy matched to the energy of
background noise. The other one is by clipping the signal to the level of background noise. The later one is chosen as default setting
because it sounds subjectively better.
Dc_rmv Description
0 Disable Dc remover
1 Enable Dc remover
Default: 1
NLP_flag Description
0
Disable NLP processing
1
Enable NLP processing
Default: 1
NLP (Non Linear Processing) is to block the small amount of residual echo which may be still audible. When NLP is enabled, user can
further enable or disable comfort noise generation. When NLP is disabled, there will be no comfort noise generation.
Freeze Description
0 Normal operation
1 Coefficient of adaptive filter is frozen (no adaptation)
Default: 0
EC Description
bypass
0 Normal operation of echo cancellation
1 Echo canceller’s output is derived directly from dc
remover output
Default: 0
Tone_flag
0
1
Default: 1
Description
Disable tone detection
Enable tone detection
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©2001 Atelic System, Inc