1
Diagnostic step 1
Capture display negotiation logs: in Console.app filter for IOKit, WindowServer, and 'display' messages during reproduction and save logs for vendor escalation. This is read-only.
FULL AI ANALYSIS
macOS Ventura: HDR video shows washed-out color and green frames on external HDMI monitor connected via Thunderbolt 4 dock
Generated Oct 3, 2026, 12:35:03 AM
Analysis summary
Behavior suggests negotiation/handshake issue for HDR color metadata or pixel format over the Thunderbolt→HDMI conversion path. The fact that direct connection works and dock connection fails implicates the dock's DisplayPort/HDMI converter or how macOS uses the Thunderbolt alt‑mode via the dock. Console EDID/stream warnings and WindowServer spikes support a driver-level interaction with display capabilities. This is likely a regression triggered by macOS update or a dock firmware/EDID handling mismatch under HDR modes.
Possible causes
EDID or HDCP negotiation failures resulting in temporary fallback to an unsupported color pipeline, causing green frames while WindowServer reconfigures framebuffer.
95%Thunderbolt dock firmware/bridge chip incorrectly handling HDR metadata (color space primaries, EOTF) or misreporting EDID causing macOS to choose unsupported pixel format.
90%Monitor reports HDR support but expects different color depth/format (e.g., requires YCbCr 4:2:2) and the dock forces incompatible format.
60%macOS Ventura regression in HDR/DisplayPort MST/alt-mode negotiation that manifests with certain bridge chips when passing HDR over Thunderbolt.
50%Suggested fixes
2
Diagnostic step 2
Test with direct USB‑C to HDMI/DisplayPort adapter to confirm dock is the differentiator (already tested — direct works). As a workaround, use the direct adapter for HDR playback until root cause is fixed.
3
Diagnostic step 3
Set Display settings to force SDR on the external monitor to avoid green frames while streaming HDR; reversible from System Settings.
4
Diagnostic step 4
Contact dock vendor with captured IOKit logs and EDID dump (use 'ioreg -lw0 -r -n IODisplayConnect' to export EDID) and request firmware patch or compatibility guidance. Do not share sensitive device identifiers publicly; provide logs only to vendor support.
5
Diagnostic step 5
If vendor cannot resolve, file a bug with Apple using Feedback Assistant including Console logs and steps to reproduce; escalate to Apple Support if you have AppleCare and need expedited troubleshooting.