During the process of certain bureau Conference TV(VP2000) openning, there was unknown origin noise many times when we debugging the equipment, the noise is quite ear-piercing, and last about 15 secends. After that, the system came back to normal again. During the noise happenning, if we cut any connectting meeting place, the noise stops immediately. After repeatly observing, we found out that the noise is related to the image switch action during the conference. The noise is after the image switch action, but not each switch action cause the noise.
Random choose some meeting place to cut connection or shut down, and keep other meeting place, the noise still emerges. It means the noise may come from MCU. After plugging and unpluging the slot or switching the slot, the malfunction exist. So, replace the BPU board, the malfunction dispear.
Only BPU processes image and sound at the same time inside the MCU, and the noise came with image, so we locate the malfunction part at BPU.