Roku will not play mp4 files encoded at certain speeds

[SolitaryBlue]

Please detail your question or problem in as much detail as possible:
Ok – I don't know if this an issue with Handbrake, or with Plex, or with the Roku:
I'm ripping DVDs for Plex using MakeMKV, then I use Handbrake to convert from mkv to mp4. I'm finding that if I set my encode speed to "Placebo" or to "Very Slow," Plex will not play the mp4 through my Roku. I get the error: "We're unable to play this video, make sure the server is running and has access to this video." They play just fine in VLC, and on Plex with the web browser.
I just upgraded from a Roku 2 to a Roku Premiere. The same thing happened with both Rokus.
I do NOT have this problem if I use an encode speed of "Slower" or above.
I suspect it might be related to AC3 audio. All of the mp4 files with this problem were encoded with AC3 Passthru. I have NOT had this issue with files encoded with DTS-HD Passthru.

For now I will keep using "Slower" or speeds above it. Just curious what might be creating this issue. Thanks for any thoughts.

Tell us about your environment. What version of HandBrake? What version of Windows are you running. etc.
Windows 10
Handbrake 1.0.7
Roku Premiere
PMS server is running from a 4TB Seagate NAS.

If there was any exception or error displayed, please copy it and paste it here:
n/a

Please include the scan or encode log:

Code: Select all

 Paste a log of the scan or encode between these code brackets, or use a pastebin website and provide us with the URL it gives you. 
 Logs are required for all support requests.

Encoded at speed "Placebo"
https://pastebin.com/qe2Lhz5a

"Very Slow"
https://pastebin.com/QYYD5N6r

"Slower"
https://pastebin.com/9ZfbZQ4y

[Deleted User 11865]

Probably the additional reference frames in the DPB. You could add "ref=5" (without quotes) to the additional options string.

[SolitaryBlue]

That worked for me. Thank you so much!