[Bug] Apple Silicon M4: AV1 to H.264 HW Transcode (VideoToolbox) causes s3014 error and severe smear

kuthedk
Mon, 27 Apr 2026 19:58:21 +0000
Plex Media Server

Environment & Versions:

Server OS: macOS 26.4.1 (25E253)

Hardware: M4 Mac Mini

Plex Media Server Version: 1.43.1.10611

Plex Web Version: 4.159.0

Plex Apple TV Version: 8.45 (9684)

Plex iOS Version: 2026.7.0 (1660) / Platform 26.4.2

iOS Device: iPhone Air (iPhone18,4) running iOS 26.4.2 (23E261)

Description of Issue: When attempting to transcode AV1 media using hardware acceleration on the Apple M4 chip, the VideoToolbox handoff to the H.264 encoder is fundamentally broken. It results in transcoder crashes (s3014) on Mac/Web clients, and severe visual smearing/macro-blocking on Apple TV 4K clients.

If the server is allowed to transcode the AV1 to HEVC instead, the hardware pipeline works flawlessly.

Testing performed to isolate the bug:

Direct Play (AV1): Plays flawlessly natively on iOS client (iPhone Air).

HW Transcode (AV1 to HEVC): Plays flawlessly on all tested clients.

SW Transcode (AV1 to H.264): Plays flawlessly.

HW Transcode (AV1 to H.264): Fails severely.

Steps to Reproduce (Using PMS Transcoder Settings):

1. Host an AV1 file on an M4 Mac Mini.

2. In PMS Settings > Transcoder, set HEVC video Encoding to HEVC Sources Only (This forces AV1 to transcode to H.264).

3. Play the AV1 file on Plex Web → Result: s3014 Error (Crash).

4. Play the AV1 file on an Apple TV 4K → Result: Severe visual smearing and stuttering.

5. Change HEVC video Encoding to Always Available (Allows AV1 to transcode to HEVC).

6. Play on either device → Result: Flawless playback.

Attachments:

Attached are the PMS Debug Logs captured immediately after the s3014 crash.

60-Second AV1 Sample File: Google Drive Link (Used to reliably reproduce the pipeline failure).

Plex Media Server Logs_2026-04-27_14-43-05.zip (5.4 MB)

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