Server Version#: 1.43.1.10611
Player Version#: 2026.8.0
Post Body:
Device: iPhone 15 (18.7.8)
Server: ZimaOS
Connection: Local Wi‑Fi (200–300 Mbps stable)
Playback mode: Direct Play
File type: H.264 High@L4, 1080p, 10 Mbps, 8 slices per frame
Audio: E‑AC‑3 JOC (Atmos), 768 kbps
Network: Stable, no packet loss
Issue Summary
When playing certain H.264 files on the Plex iOS app on iPhone 15, I experience micro‑stutters every 15–30 seconds.
The stutters occur exactly when the Plex iOS client performs a burst download.
On my server’s network graph, the iPhone shows:
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periodic 20–25 MB spikes
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long pauses
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then another spike
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micro‑stutter at the moment of the spike
This behavior is consistent and 100% reproducible.
Important Comparison: iPad 7th gen (ios 17.7) vs iPhone 15
I tested the same file on my iPad (same Plex iOS app, same server, same Wi‑Fi).
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The iPad shows the same burst‑buffering pattern in the network graph
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But the iPad has zero stutter
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Playback is perfectly smooth
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No frame drops, no audio/video hiccups
Expected Behavior
Smooth playback with continuous streaming or stable buffering, similar to:
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Plex Web (PC)
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Plex Desktop
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Infuse (using the same Plex server)
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iPad (same Plex iOS app)
All of these play the same file perfectly.
Actual Behavior on iPhone 15
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Plex iOS uses burst‑style buffering
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The iPhone 15 hardware decoder stalls briefly when the buffer refills
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This causes micro‑stutters exactly at each burst
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The iPad does not have this problem
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Infuse does not have this problem
This points to a device‑specific decoder issue triggered by Plex’s buffering strategy.
File Details (MediaInfo)
The video stream contains:
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H.264 High@L4
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10 Mbps
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8 slices per frame
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4 reference frames
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1080p / 23.976 fps
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CABAC enabled
This file Direct Plays correctly on all other Plex clients.
Reproduction Steps
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Play the file on iPhone 15 Plex iOS
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Observe micro‑stutters every few seconds
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Check server network graph → burst spikes
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Play the same file on iPad Plex iOS → smooth
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Play the same file on PC Plex → smooth
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Play the same file in Infuse → smooth
The issue is reproducible 100% of the time on iPhone 15.
Conclusion
This appears to be a Plex iOS playback engine issue specific to iPhone 15, where burst‑style buffering causes decoder stalls on certain H.264 files (especially multi‑slice encodes).
A continuous streaming mode or larger buffer on iOS would likely resolve the problem.
I can provide logs, additional MediaInfo, or network graphs if needed.
Here is the sample network graph showing the burst spikes during playback:
