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Level 7

Roku Express (new version) - h.264 Reference Frames - Plex Direct Play / Transcoding

Diving straight in on my first post - I did have a dig around via search, but couldn't find something specific to the problem.

I have a new version (Dec 2019) Express streaming player.

Lately we have noticed thatwhen playing Plex content its forcing Transcoding over direct play.  After some digging (a more techy friend that me) said that its to do with "reference frames".

In Plex a 720p H264 4.1 media files with higher than 9 reference frames do not "direct play" on the Roku, which forces Plex to transcode. Anything lower than 9 reference frames are fine.

I would have thought if the file was encoded higher than the H264 specification, we would see this behaviour on other plex clients (iOS, Firestick as examples). Could "other players" be using the h264 5.1 standard which supports higher reference frames? And because the Roku does not support 5.1 it is incapable of direct playing these files. (Just an idea)?

Is there a set h.264 standard that the Express uses, and if there is, is this likely to be increased or be user set?

I can set h.264 in the Plex app on the Roku, but this doesn't make a difference to playback.

This is from the Plex forums Plex Forum Post 

The main issue is that I run Plex on my Synology, so the Transcode overhead is impacting performace of the NAs, as its not super powerful as a PMS.


Thanks to anyone that can offer any insight...

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Level 7

Re: Roku Express (new version) - h.264 Reference Frames - Plex Direct Play / Transcoding

I have a Roku 3 and use Plex. I routinely come across video with 12 reference frames (refFrames). I have found a solution for direct playing the video from Plex, without any transcoding. A few caveats. I mostly play 720p, and so I can't vouch for 1080p content. Second, this is a hack, and not officially supported, so it could cause playback problems, may void your warranty, cause your house to explode, produce a black hole, etc, etc. You were warned. That said, I have been doing this for over a year now, and have never had a single problem with it.

The hack is simple. Find the Plex profile file for the Roku. On my Windows machine it is "C:\Program Files (x86)\Plex\Plex Media Server\Resources\Profiles\Roku-7.x.xml". In that file locate the line:

<UpperBound name="video.refFrames" value="8" /> 

and change the value to 12, so it looks like:

<UpperBound name="video.refFrames" value="12" />. 

Restart the Plex Media Server. When you update your Plex Media Server you may need to fix the file again, since updates sometimes overwrite them.

That's it. Like I said, it has worked flawlessly for me for over a year. It allows me to "Direct Play", or at "Direct Stream" with video copy, all my 720p content with up to 12 reference frames.

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