Crestron qm-ae Manuel D’Utilisation

QuickMedia™ Audio Extractor 

 

Crestron QM-AE 

You must pass audio through from transmitters to receivers even if you are not 
using the audio signal. The information required for auto-compensation is 
transmitted along with the audio. In addition, the QM Link signal indicates that 
the QM cable is connected and that an audio signal is present on the cable. If a 
unit does not receive an audio signal, the QM Link signal will not go high, and a 
valid QM Link connection cannot be detected (video can still be displayed if 
auto compensation is not used).    

Certain devices terminate and re-initialize the audio path within the unit; 
however, they pass on the video untouched. This creates different path lengths 
for the video and audio. This difference in path length creates different peak and 
boost levels for audio and video.  When audio-breakaway is implemented, the 
audio and video paths are likely to be different.  

Inherently, twisted pair cables experience a loss of bandwidth and signal 
strength over distance. When the loss is within certain limits, the reduced signal 
can be restored through peak and boost compensation adjustments. The amount 
of required compensation is directly dependent on the length of the cable. 
Therefore, each device in a network requires a specific amount of compensation.  

In a manual compensation system, the compensation parameters, along with 
microphone equalization settings, are stored in the receiver in a preset file. 
When the program switches to a new transmitter, the program recalls the 
compensation settings associated with the new transmitter. In large systems 
containing multiple transmitters and receivers, these parameters must be stored 
in multiple locations, creating a complex arrangement. 

In a system utilizing auto compensation, the peak and boost values are stored in 
a preset file at the receiver. The transmitter stores the input compensation and 
microphone EQ settings. When the program switches to a new transmitter, the 
transmitter ID, input compensation, and microphone EQ settings are sent over 
the audio channel of the QM cable to the receiver.  The receiver is equipped 
with a hunt algorithm to search for the proper peak and boost settings. Once the 
receiver acquires a QM Link signal, it can receive the audio signal containing 
the transmitter ID, input compensation, and microphone EQ settings. After 
receiving the transmitter ID, the receiver recalls the peak and boost preset and 
uses these values to properly adjust the video signal. 

NOTE:  If auto compensation is used in your QM system, all QM devices must 
use it. If it is not used in your QM system, it must not be used for any of the QM 
devices.