1. Write the route table
List every source down the left and every independently controlled display or audio zone across the top. Mark which source must reach which destination and whether different destinations must show different sources simultaneously.
- Many sources to one display: switch.
- One source mirrored to many displays: splitter or distribution amplifier.
- Many sources independently routed to many displays: matrix.
- Multiple sources composed on one screen at once: multiviewer, not an ordinary switch.
Select the device class, then reserve the required ports.
2. Choose one explicit EDID policy
The source chooses an output mode from the capabilities presented upstream. A router may present a lowest-common-denominator EDID, copy one display, use a fixed stored profile, or provide more advanced per-input management. These policies are not equivalent.
When displays differ, a copied or fixed high mode can exceed a weaker display. Per-output downscaling can solve some resolution mismatches only when the exact device declares it. It may not convert refresh rate, HDR, color space, VRR, audio formats, or every unusual timing.
Screen the mixed-display plan before purchase.
3. Draw audio as a separate arrow
TV apps originate audio at the TV and normally need ARC/eARC or a TV audio output. An external player can send audio through the TV, through an AVR, or to an extractor in the distribution path. An eARC soundbar input is not the same as an ordinary HDMI input, and an optical extractor does not preserve every high-bitrate format.
Plan where audio leaves the HDMI path. Confirm the requested audio format at every segment instead of inferring it from the connector name.
4. Treat features as a chain
Resolution and refresh, HDR, VRR, audio, CEC, ARC/eARC, and content protection are separate declarations. Every active router, extender, receiver, and cable segment must support the intended path. Keep protected-content troubleshooting compliant; the goal is to verify the declared path, not defeat protection.
5. Isolate from the shortest known-good path
- Connect one source directly to one display with a short known-good cable.
- Insert the router with one input and one output only.
- Add outputs one at a time and record when the negotiated mode changes.
- Swap only one input cable, output cable, source, or display at a time.
- If a lower mode works, investigate bandwidth and exact processing claims. If only mixed displays fail, investigate EDID and per-output scaling first.
Build the next isolation test.