ProjectorTestHDMI TROUBLESHOOTING LAB

← Normal fullscreen test patterns · This is an experimental video-routing lab, not the main computer test screen.

iPhone → USB-C → HDMI

Get out of the phone-shaped box.

A 1080p file can still appear small inside a mirrored phone screen. Try Apple's native video paths, then verify the actual signal on the projector. This page cannot force or detect HDMI routing.

01 / Compare playback paths

1920 × 1080 · 16:9 · SAR 1:1

Loading source metadata…

Try one launch method at a time. Return from fullscreen, then reset the player before comparing another method; this reloads the same source from the beginning. Keep fit enabled: no pinch-to-fill, stretching or cropping. The AAC track contains digital silence; it is deliberately unmuted. This tests a routing heuristic, not a documented Apple workaround.

Still small in Safari? Download the MP4 to Files and open it in Apple's built-in viewer. No app installation, but playback behavior is device-dependent. HLS tests need a network connection; this lab does not promise offline streaming.

Player diagnostics — not HDMI diagnostics

    

    

      
02 / Prove the output, not just the file

      
    
        
  1. On the projector, open Input / Signal Info. Record the incoming raster and scan/rate. For true 1080p transport it must say 1920 × 1080, progressive. A 4K input carrying a 1080p file is not a 1080p HDMI signal.
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  2. Turn overscan off. Use a geometry-preserving aspect mode. Confirm the outer border and all four corner markers are visible. The circle should be round and grid cells square.
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  3. Measure the chart's outer border. height = width × 9 ÷ 16. Compare its width and height with the computer's output using the same projector settings.
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  4. Only trust a route after unplug/replug and a second playback test. Native fullscreen on the phone is not proof of clean fullscreen video on HDMI.
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One-pixel mapping is a separate test. A 16:10 or 4K projector may scale a valid 1080p input. Compressed 4:2:0 H.264 is not a lossless pixel or broadcast-code reference.

      

        

        
        
        

        
Manual observations stay on this device. No HDMI connection is inferred. A recorded success is not automatically certified.

      

      

    

    

      
03 / If every path stays small

      

        
Phone mirroring can fit twice. A 16:9 chart fitted inside a ~19.5:9 phone, then mirrored into a 16:9 sink, can occupy about 82% of both width and height. A mirrored phone screen itself may occupy full width but only ~82% height. These are clues, not a diagnosis.

        
1080p timing is a different problem. In Settings → Display & Brightness → connected display, try SDR and compare Allow Display Mode Changes off/on. Apple documents matching frame rate and dynamic range, not a manual 1080p resolution selector.

        
Negotiate rather than zoom. If your projector offers an EDID preset, try one advertising 1080p only and reconnect the cable. An external EDID emulator can constrain the modes advertised to the iPhone; a scaler can fix its own output at 1080p. Neither removes phone-shaped mirroring by itself.

        
CSS cannot change the HDMI clock. Enlarging the page, pretending the video is anamorphic, or zoom-to-fill can crop or distort the chart. A PWA does not gain external-display APIs. If all Safari paths remain mirrored, this web app cannot guarantee a dedicated video output on that setup.