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

Environment

MacBook Pro running macOS 13.5.2 with integrated Intel/Apple Silicon graphics, Apple TV 4K on same home Wi‑Fi (802.11ac), both devices show as 'Connected' in Control Center and TV app; AirPlay used for screen mirroring and app video streaming.

Symptoms

When initiating AirPlay mirroring or streaming video from Safari/QuickTime, audio is heard on Apple TV but the TV shows a black screen; the TV indicates an active AirPlay session and client device name. Local display on Mac shows normal contents while mirrored window on TV stays black.

Observations

Console logs on macOS show repeated AirPlayVideoEngine warnings during mirroring attempts (timestamps aligned with session starts). Wireshark capture on Wi‑Fi AP shows steady UDP/RTP/RTCP packets from Mac to Apple TV's AirPlay ports; packet sizes and intervals indicate video frames are being sent. On Apple TV, the system log shows 'unsupported surface format' entries intermittently. Mirroring works correctly when using wired Ethernet for Apple TV and a different MacBook running macOS 12.6 on same network, and Safari video casting to TV via a native app works with audio and video.

Already attempted

Restarted both Mac and Apple TV, toggled AirPlay in Display preferences, created a new local user on Mac and reproduced issue from that account, reset Apple TV display settings, disabled 'Use HDR' and 'Match Dynamic Range' options, tested with different Wi‑Fi channel and 5 GHz vs 2.4 GHz bands, temporarily disabled Content Blocking extensions in Safari. Rebooted Wi‑Fi AP and placed Apple TV on wired Ethernet to isolate wireless; wired connection restored both audio and video mirroring.

Question

Given RTP/video packets are present but Apple TV shows no video when both devices are on Wi‑Fi while wired connection works, what diagnostics and reversible mitigations can identify whether this is a macOS AirPlay encoder/format negotiation issue, a Wi‑Fi multicast/unicast fragmentation problem, or an Apple TV surface-format incompatibility introduced after the OS update?

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AI DIAGNOSTICS

Incident analysis

Updated 1w ago• Trouble ID

Most likely 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%

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.

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.