Thank you. I have been using the zybo with 1080p in different devices (two monitors and one frame grabber) without problems. It may have something wrong with my design when I rebuild the base overlay from pynq to zybo. Even at 720p it is not working. After hdmi_in.start() and hdmi_out.start() the computer blinks but no video signal is detected.
Also, when I try to run hdmi_in.readframe(), this error is shown: RuntimeError: DMA channel not started.