Screen mirroring lag so much-galaxy s3 topic

Hi guys, i have a galaxy s3 with archidroid, and i've just buy a chromecast. Play music and YouTube run smooth but when i try to do the screen mirroring it lags so much, even the phone lags, and i dont know why. I have a 20 mbps connection, and the device is just 2 meters from router...i see that device like nex 5 runs very smooth, there are something i can do?

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