Buffering when transcoding to HVEC

Plex Media Server NAS & Devices
1

Server Version#: 1.18.7.2438 Synology 218+
Player Version#: 6.7.2 iOS

I have recorded TV 1080i (MPEG2VIDEO) (hw) that I play on different devices. When Plex transcodes this video to 1080P (H264) — Transcode (hw) the video plays fine. However, when Plex transcodes to 1080P (HEVC) — Transcode (hw), I get 2 seconds of playback, then buffering along with the message “The server is not power enough to convert this video for smooth playback”, then the video buffers for ~90 seconds, plays for ~120 seconds, buffers for ~90 seconds, etc… I have hardware accelerated encoding enabled (things get much worse with it disabled). I assume this transcoding to HVEC is maxing the hardware encoder?

This behavior is only seen on my iOS client - presumably because this client supports HVEC; while other clients support H.264. Is there a way to control transcoding so Plex just transcodes to H.264? Or another solution I’m not considering?

2

Plex doesn’t output HEVC. It outputs H.264.

Can you show me DEBUG logs please?

3

Pretty sure I’ve seen a couple of threads showing HEVC transcoding to IOS devices only. Here’s one:

4

tested just now.

Screenshot from 2020-02-19 22-49-33 Screenshot from 2020-02-19 22-50-14

5

Here is the behavior I’m seeing. The stream on the left is being transcoded to H.264 and works. The stream on the right is being transcoded to HVEC and has significant buffering.
image

Debug logs attached.
Plex Media Server Logs_2020-02-20_22-44-38.zip (3.9 MB)

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6

I am definitely not understanding.

  1. There should be no HEVC reported as the target.
  2. HEVC UHD -> iPhone XR as shown below
    Screenshot from 2020-02-21 13-52-48

Please give me a bit to go through these logs.

7

hevc encoding seems to be in some kind of testing phase for specific client/server hardware combinations.

whether or not it is supposed to be public, is unknown.

but either way, something is going on, chuck might want to check with other team members.

1 Like
8

Maybe I’ve misunderstood this post, but I interpret it as transcoding to HEVC is actually a possibility for some devices and/or servers.

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9

I have chatted with Otto and we did sort it out.

10

Supplemental.

We are discussing further with Engineering.

While logs do show transcoding to HEVC, this should not be happening.

11

keep in mind, people want hevc encoding (where compatible with client).

12

I understand it is much requested.

Not everyone can have it due to device limitations. As it being seen now, the iOS client is accepting HEVC DirectPlay / DirectStream.

Further, not all servers can reasonably produce HEVC due to the complexity of encoding it versus the resources available. Some CPUs do not have the required power.

13

@TeknoJunky

I’ve done more digging.

It appears:
H.264 -> HEVC (H.265) won’t happen
HEVC -> HEVC can happen if and only if already in fMP4 layout.

I will further verify with the iOS, transcoding and server teams on Monday.

14

I appreciate all the verification. As the HEVC transcode feature is developed, I wonder if there can be a knob to control its use? It’s clear that at 1080, my little Synology 218+'s Celeron J3355 just can’t quite encode in real-time.

15

There is a knob to control its use but that knob is hard coded.
It also requires a player which can meet the requirements.
Not all players are capable of fragmented MP4 (fMP4)

16

Now that I know what is happening, I have been able to tweak the quality setting in the iOS app for Home Streaming to 8 Mbps 1080p HD. This is resulting in h.264 encodes to iOS devices. This is enough of a knob for me to get streaming performance back where it needs to be for my setup.

17

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