Try a shorter cable?

- Tom

Ahem...but no. Normal HDMI cables are passive, so not directional.

<aside>Talk of directional cables take me back to irrational claims by high-end audio manufacturers, which literally makes my blood pressure go up.</aside>

According to https://en.wikipedia.org/wiki/HDMI

"Although no maximum length for an HDMI cable is specified, signal attenuation (dependent on the cable's construction quality and conducting materials) limits usable lengths in practice and certification is difficult to achieve for lengths beyond 13 m"

You very likely need an HDMI extender.

"Extenders
An HDMI extender is a single device (or pair of devices) powered with an external power source or with the 5V DC from the HDMI source.[81][82][83] Long cables can cause instability of HDCP and blinking on the screen, due to the weakened DDC signal that HDCP requires. HDCP DDC signals must be multiplexed with TMDS video signals to comply with HDCP requirements for HDMI extenders based on a single Category 5/Category 6 cable.[84][85] Several companies offer amplifiers, equalizers and repeaters that can string several standard HDMI cables together. Active HDMI cables use electronics within the cable to boost the signal and allow for HDMI cables of up to 30 meters (98 feet);[81] those based on HDBaseT can extend to 100 meters; HDMI extenders that are based on dual Category 5/Category 6 cable can extend HDMI to 250 meters (820 feet); while HDMI extenders based on optical fiber can extend HDMI to 300 meters (980 feet)."

In the past I bought this cheap HDMI extender to run a signal across my office. It was just $25. It's adequate, but it absolutely requires a good quality Cat5e or Cat6 cable or it simply doesn't work.

Unlike passive cables, cables with active electronic repeaters and extenders ARE directional, without being irrational.

Yes i use that kind of hdmi 20m long and have internal chip, input and output side.