FULL AI ANALYSIS

AirPlay to Apple TV: audio plays but mirror/stream shows a persistent black video window after macOS display update

Generated Oct 3, 2026, 12:35:03 AM

Analysis summary

The core evidence: RTP video is sent but the Apple TV fails to render video when both endpoints are on Wi‑Fi, while wired connectivity to the TV resolves the issue. This strongly suggests the problem lies either in the network (loss, fragmentation, MTU/multicast handling) or in the negotiated video surface/format under wireless conditions (encoder choosing a surface that the Apple TV cannot map when delivered over Wi‑Fi). The device-specific success on macOS 12.6 and with wired Apple TV points away from a complete network outage and toward a change in the macOS AirPlay video path or a timing-related packet loss/ordering problem on Wi‑Fi that breaks the TV's decoder/surface creation.

Possible causes

AirPlay video encoder or surface negotiation bug in the macOS video pipeline causing a surface format the Apple TV cannot instantiate over lossy Wi‑Fi.

75%

Apple TV firmware incompatibility with the new AirPlay frame format sent by updated macOS, but only triggered when wireless transport uses different timing or packetization.

70%

Wi‑Fi fragmentation/MTU or driver-level packet loss under wireless that corrupts initial key frames or session negotiation packets, leading Apple TV to drop video frames but still accept audio (audio uses smaller/robust packets).

35%

Multicast/Broadcast or AP client isolation settings on AP causing control or encryption handshake frames to be lost, preventing shared surface creation.

10%

Suggested fixes

Diagnostic step 1

Reproduce with packet capture: run tcpdump/Wireshark on the Wi‑Fi AP (or on the Mac via 'sudo tcpdump -i en0 -w airplay.pcap udp port 5000 or udp port 6000') during a mirroring attempt and compare keyframe/RTP sequence behavior between working (wired Apple TV) and failing (Wi‑Fi) runs. Share captures with vendor support if requested.

Diagnostic step 2

Test with a different Wi‑Fi network or a phone hotspot to rule out AP-specific multicast/fragmentation settings; if working on another network, inspect AP settings: disable client isolation, check MTU, turn off IGMP snooping and 802.11w Robust Management Frames temporarily.

Diagnostic step 3

Temporarily reduce Mac's display resolution and mirroring frame rate (Scaled Resolution, lower refresh) to see if smaller frames avoid the issue; if that works, it points to MTU/fragmentation or encoder bitrate problems.

Diagnostic step 4

Boot Mac into Safe Mode and test AirPlay to rule out third‑party kexts or video filters interfering with the video pipeline. Also create and test a new local user (already done) to rule out per-user config.

Diagnostic step 5

If packet captures and configuration adjustments don't identify a network cause, collect macOS Console logs (filtered for AirPlayVideoEngine/AVD messages) and Apple TV syslogs, then escalate to Apple Support with the logs and pcap for deeper analysis; until vendor analysis completes, prefer wired Apple TV for critical presentations.

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