macOS app: video goes black during direct play while audio continues (Apple TV / iOS fine)

[ledrum 0]

macOS app: video goes black during direct play while audio continues (Apple TV / iOS fine)

CLIENT
- Emby for macOS 2.2.58 (Mac App Store, com.emby.mobile)
- MacBook Pro, Apple M5 (Mac17,2), macOS 27.2 (26B5101f)
- Built-in display + two external 1920x1200 displays

SERVER
- Emby Server 4.10.1.0 on Fedora 44 (native RPM), Intel i5-9500T, Quick Sync available
- Library on SMB/CIFS from a NAS. Client and server are on the same LAN.

PROBLEM
After playing for a while the video goes black but audio keeps playing. At the same time the player UI resets: the progress bar jumps to the start, the time shows --:--, and the play button shows "play" as if nothing is playing. It has happened on both movies and TV episodes. The same items play without problems in Emby on Apple TV and on iPhone, on the same server and network.

REPRODUCED TODAY WITH
- Video: HEVC Main 10 (yuv420p10le), 1920x800, 23.976 fps, about 2 Mbit/s
- Audio: AAC LC 5.1
- Container: MP4
It failed at roughly 1:14:15 into a 2:25:00 file.

WHAT I TESTED
1. Direct play of the original file (hev1 tag): FAILS, video goes black.
2. Direct play of a remux with the tag changed to hvc1 and chapters removed (no re-encode): FAILS, video goes black.
3. Quality set to 720p 1.5 Mbps, which forces server transcoding to H.264 (hevc_qsv to h264_qsv): WORKS, played without problems.
4. Full decode of the file on the same Mac with ffmpeg -hwaccel videotoolbox: WORKS, 0 decode errors, all 208,606 frames.
5. Same file in the Apple TV and iPhone apps: WORKS.

The file decodes cleanly on this Mac's hardware decoder, and container details (hev1/hvc1, chapters) make no difference. The problem seems to be in the macOS app's direct play path.

UNKNOWN
I can't confirm whether earlier occurrences were all HEVC. Part of my library is H.264 in MKV, and I haven't yet tested whether direct play of H.264 also fails.

WORKAROUND
Choose a quality below the source bitrate so the server transcodes to H.264.

Happy to provide server logs or run further tests.
 

Edited 3 hours ago by ledrum
copy/paste messed with the text