Audio DSP with AEC, 4-in/4-out analog, 4-in/4-out Dante and USB
-19-
(2) Channel control parameters
AutoMixer:
Each channel has an automix on/off button which must be turned on for channels to participate in the automix.
Mute:
Both channel mute and fader are behind auto gain. If the channel level is increased, the gain level of other channels may
also be reduced even if the channel mute is on.
Gain:
Gain fader for adjustment will increase/decrease the volume proportion in automix.
Priority:
Priority setting for automix algorithm. Priority parameter ranges from 0 to 10. Higher value gives
higher priority.
Both channel mute and fader are behind auto gain. Any adjustment made in these two parameters will not
influence the operation of the automix. For example, If the channel level is higher, the level gain of other
channels may be reduced even if the channel mute is on. Channel mute shall be turned on and automix
shall be turned off to mute the signal and prevent its influence on the automix. Mute button at each channel
shall be muted and directly connect output mute when mixing sound. Channel faders also control sound
mixing level and direct output level of channels.
Priority control allows high priority channels to override low priority channels, and thus the automix algorithm
will be affected. Priority value can be set from 0 (the lowest priority) to 10 (the highest priority), and the
default value is 5 (standard priority). Users may use slider or click textbook to input a specified priority
between 0 and 10 to adjust priority.
If two channels have the same signal level, then the channel with higher priority will get more auto gain. If
there is one-unit priority between them, then the channel with higher priority will get extra sound mixing gain
of 2dB (suppose the slope of the two channels is set at 2.0). For example, if channel 1 and 2’s priorities are
respectively set at 6 and 3, and the input level of those two channels are the same, then channel 1 will get
extra sound mixing gain of 66dB than channel 2. During operation, it shall be noted that the slope setting of
main control parameters will also influence sound mixing gain difference brought by the priority weight of
channels. If the slope is set at 3.0, then one priority unit difference will result in gain difference of 4dB. If all
channels have the same priority, then their priority settings shall be set at 5.
Note: Users should be very careful when using high priority differences between channels, such as priority of 0 and 10. If
channels with high priority recognize signals like background music from speaker, then it is possible for them to mask channels
with lower priority even the former is not used. It will get worse if the slope is higher. To prevent this users may consider installing
a noise gate or expander between automixers at the highest priority channels. Threshold should be set at the level where it is
not opened by the noise gate or expander.
3.3.8 Acoustic Echo Cancellation (AEC)
To use the AEC module, select the local microphones to be processed, select the input from the far side talker and do the
appropriate routing of the AEC channel in the matrix.
Acoustic echo cancellation (AEC for short) is a type of digital audio signal processing to improve. It is used in audio/video
conferencing when talkers in the local conference room are talking with one or more speakers at a remote location. AEC
improves the remote talkers experience by cancelling acoustic echo generated in the local room.
Echo cancellation module for remote calls can be used for local amplification of remote voice signals and attenuate the
interference caused by acoustic echo. Its basic operation principle is simulating the echo channel, calculate the echo generated
by remote signals and then subtract the estimated signal from the input signal from microphones.
There is one echo cancellation module in the Tight DSP unit. Two local input and remote output mixers are preset to realize
multichannel signal participating echo cancellation as shown in the figure. One parameter can be adjusted:
Non-linear filter (NLP):
Three types including Conservative, Moderate and Aggressive can be selected to determine echo
suppression levels.
