Canon LEGRIA HF G25 HDMI output to RF h264 Latency

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I view live Coax feed while I shoot via HDMI out put, I use HDMI Modulator, when I set MPEG2 - latency is fine, but when I set H.264 codec it goes up to 300ms, I tried the same thing with Sony camcorder - It works fine with both MPEG2 and H264, Why?