4K playback stutters & endless buffering when direct playing in Plex for Mac (only)

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1

Hi!

Trying to (direct) play a bunch of 4K h.264 encoded files in Plex for Mac I see a slideshow basically. The playback stutters and the app buffers all the time. It can never play back smoothly any portion of any 4K/h.264 file.

I use a wired gigabit ethernet connection between PMS and a MacBook Air running Plex for Mac (as well as Apple TV).

All my Plex clients are configured to use the direct play feature.

However, Plex for Apple TV works like a breeze.

I can also play back same files directly (SAMBA share) with QuickTime Player on the same host where Plex app for macOS fails just fine .

Basically, what we’re looking at:

  • The host running PMS is more than capable for the task.

  • I observe a 6-12% CPU utilization on a 6-core CPU when trying to play back the 4K files mentioned above.

  • There’s about 15GB of free RAM available.

  • The disk I/O is mostly idle and an average throughput is at least 100MB/s averaging about 180-220MB/s in most workloads. My 4K files have a varying bitrate of 60-100 Mbps.

  • The gigabit ethernet connection is solid and performs up to the spec.

  • Same 4K files are perfectly playable directly from the same host running Plex for Mac using QuickTime Player.

Software

  • Plex Media Server version 1.29.2.6364-6d72b0cf6 (Ubuntu 22 LTS)

  • Plex for Mac Version 1.58.1.3380-ea159c52 (macOS Catalina 10.15.7; MacBook Air 11" mid-2012)

  • Plex for AppleTV 7.24 (1284) (tvOS 16.1 (20K71); Apple TV 4K Model A1842 (32 GB))

1 Like
2

This is going to require player logs to diagnose further. However, your GPU in the MBA is quite weak and it may not even be capable of decoding 4k H.264 in hardware. Try disabling hardware decoding in the settings to see if that performs differently.

3

Hi, I can play back same files directly (local disk or SAMBA share, doesn’t matter) with QuickTime Player, or VLC, on this MacBook Air.

It’s only a problem when Plex for Mac is used as a player. Disabling hardware decoding didn’t make any difference.

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