2017 Base i5 struggling with Streaming 4K Plex

Discussion in 'iMac' started by c613m, Jun 27, 2017.

  1. c613m macrumors 6502

    c613m

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    #1
    Just received my iMac this morning, was just about to test a 4K through Plex to Xbox One S, and to my surprise, it seems to be pushing this Mac to the limit. CPUs all hit 95% to 100%, and every 20 seconds or so the movie stutters.

    Both the iMac and the Xbox are hard wired via ethernet, as far as I can tell, the Plex settings are maxed.

    Any ideas? I can't justify the 3K I spent on this and can't even stream my 4K movies through Plex.

    i5 3.4Ghz, 24GB's RAM, 512SSD.
     
  2. SnowLucas macrumors member

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    Feb 19, 2015
    #2
    I'm no expert but if your 4K files are in HEVC rather than h264 then this would be fairly expected behaviour until you can get hardware decoding in the next macOS. Have a look at what file type you are using and see how it plays locally.
     
  3. c613m thread starter macrumors 6502

    c613m

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  4. Taz Mangus macrumors 68040

    Taz Mangus

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    #4
    It play fine locally then it sounds like the issue is with Plex.
     
  5. c613m thread starter macrumors 6502

    c613m

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    #5
    Well that sucks, a big part of me upgrading from my 2011 iMac was for this.
     
  6. theluggage macrumors 68030

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    #6
    ...does the XBox have native support for whatever format you're using? If not, plex on the Mac might be trying to transcode it on-the-fly to a format the xBox supports, which will hammer the CPU.
     
  7. c613m thread starter macrumors 6502

    c613m

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    #7
    How would I be able to check that? I'm testing right now on my KS8000, and the same file is playing fine with 1-2% CPU usage... did I just upgrade my Mac for nothing?? lol
     
  8. Taz Mangus macrumors 68040

    Taz Mangus

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    #8
    What is the CPU usage when you play it locally? If it is not high then the issue is with how Plex is transcoding.
     
  9. c613m thread starter macrumors 6502

    c613m

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    #9
    CPU's hovering between 95% and 100%, and on the Server it's transcoding from HEVC to H264,
     
  10. EugW macrumors 68000

    EugW

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    #10
    Hmmm... I'm not a Plex guy, but the main advantage of Plex IMO is to transcode on the fly to formats that are either easier for the client to decode or else compatible for the client, or both.

    If you're trying to do that with 4K HEVC via software decoding, then good luck. Even my Core i7 would have trouble on some 4k HEVC material (unless you were using hardware decoding/encoding).

    And given that you're hammering the CPU, it sounds like you are indeed trying to software decode and software transcode at the same time.

    A better solution if possible would be to have a client that can just natively decode the files, and leave the iMac out of it completely (although I understand that is difficult with 4K material).
     
  11. c613m thread starter macrumors 6502

    c613m

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    #11
    Crap, I was under the impression that this would be able to handle streaming 4K through Plex. If I tell my wife that it can't she'll kill me and make me return it LOL.
     
  12. EugW macrumors 68000

    EugW

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    #12
    It might help to know the specs of your files (codec, bit depth, bit rate, profile, container, etc.) and for the people with more Plex knowledge, what the Plex transcoding settings are.

    If you had hardware transcoding, you could do it. Does Plex on the Mac allow hardware HEVC transcoding now? Cuz as of last year it was only h.264 AFAIK.
     
  13. c613m thread starter macrumors 6502

    c613m

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    #13
    HEVC codec I believe. Both Xbox One S and PS4 are no go for smooth play. If I stream through my KS8000 then I'm good (apart from some files that says unsupported audio)... but now I'm sitting here wondering if I would've been fine without upgrading.
     
  14. Taz Mangus macrumors 68040

    Taz Mangus

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    #14
    The Xbox One S can't play 4K videos through streaming?
     
  15. c613m thread starter macrumors 6502

    c613m

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    #15
    Apparently not HEVC codecs. I mean, it plays them, but forces transcoding through Plex in which the iMac just can't keep up.
     
  16. SnowLucas macrumors member

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    #16
    If you have bought the iMac just to stream 4K files to the Xbox then I'd suggest that's not a very good solution. An Nvidia shield could play those files nativity and obviously cost a fraction of the cost of the iMac (even a few nvidia shields). There are a few devices that can do this, one I like is made by a company in the UK and is called the Vero 4K.

    You're best checking the plex forums to see if the Xbox one plex client supports HEVC now or will in the future. If it does, again a new iMac isn't really needed over any other computer that can run plex server.

    Finally High Sierra should add hardware HEVC decode support when it comes out. That would make what your trying to do work much better (much lower cpu usage) and is limited to a small selection of Apple computers of which I beleive yours is included.

    So if the Xbox doesn't do hardware decoding of HEVC files (in plex) and you don't want to buy different hardware to run along side the Xbox(Nvidia shield) then the iMac might be right for your needs. You just need to wait for High Sierra (you could try the public beta when that comes out to confirm that it works as you need).
     
  17. EugW macrumors 68000

    EugW

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    #17
    IIRC, when Apple added hardware h.264 support, it took many moons before third parties had functional hardware h.264 support in their software.
     
  18. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

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    #18
    Yes, you can direct stream 4k HEVC content to an Xbox in Plex, as long as the codec and container is right, and you don't have subtitles (!). So your movie must be deviating somehow, in a way that the Xbox doesn't support it, therefore there will be transcoding.

    See this.
     
  19. gian8989 macrumors regular

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    #19
    I never use the mac for plex (have shield tv) but are you using the app or streming with browser?
     
  20. joema2 macrumors 65816

    joema2

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    #20
    The iMac can probably handle streaming 4k H264 through Plex -- I can smoothly stream 4k from Youtube or Vimeo on my 2015 iMac 27. But your Mac cannot currently handle 4k HEVC. You have apparently acquired or encoded videos on your Plex server as HEVC. That means whatever plays that back must decode it. HEVC is incredibly compute intensive and generally requires hardware acceleration for smooth playback. Your KS8000 TV probably has HEVC acceleration hardware, thus it can play it smoothly.

    The 2017 iMac 27 has a Kaby Lake CPU with Quick Sync upgraded to 10-bit 4k HEVC decoding, but the application software (ie playback app) must support this, and maybe also the OS itself. E.g, Quick Sync for H.264 has existed since 2011, yet Premiere Pro still does not support this on Macs, so there can be a significant lag between hardware and software support.

    To my knowledge, Plex does not support hardware-accelerated HEVC transcoding on the server side -- it can only stream whatever the encoding format is. Your iMac has a Kaby Lake CPU so the hardware support for HEVC decoding is there; you only need the proper software to support this. I don't think VLC supports this (at least on Mac).

    Supposedly macOS High Sierra will have HEVC support. This will vary based on what CPU hardware generation: http://www.anandtech.com/show/10610...six-notebook-skus-desktop-coming-in-january/3

    For Kaby Lake CPUs there will be full support for 4k 10-bit HEVC. The nature of this support may mean OS and library support for developers writing new playback and streaming software, and maybe QuickTime Player and FCPX will be upgraded to use HEVC. Until then, unless you can find some Mac playback software which supports HEVC you will have to wait.

    I think Plex may be adding streaming transcoding for HEVC on the server side, so it can do live transcoding from (say) HEVC to H.264. That would also possibly solve your problem. However this is apparently only in beta.
     
  21. jclardy macrumors 68040

    jclardy

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    #21
    Hardware HEVC decoding is supported in High Sierra for most machines newer than 2015...so you could try installing the public beta when it is released in the next week or so.
     
  22. c613m thread starter macrumors 6502

    c613m

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    #22
    I'm not sure that High Sierra will help as it's Plex telling the Mac to do the encoding.

    The Mac can handle playing them natively just can't encode as fast as the stream to Xbox.
     
  23. joema2 macrumors 65816

    joema2

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    #23
    If Plex is the server and the iMac the client, the iMac is *decoding* the HEVC content, not encoding it. Are you doing that or are you running the Plex media server on your iMac and streaming the content to your XBox as the client? In that case the iMac might be transcoding from HEVC to H264 if the Plex client software on the XBox indicated it can't handle HEVC. Are you connecting to a TV via HDMI from the Xbox, from the iMac or are you streaming from to an iMac client from some Plex server for display on the iMac?

    When you copy the HEVC file to the iMac and play it locally, is that using Quicktime Player, VLC, the Plex player, or what? Each one will have different performance characteristics.

    The bottom line is these are all Plex questions, not iMac questions. There are no iMac or macOS config options to adjust which affects Plex streaming or playback. You'll probably get a better answer on a Plex forum.
     
  24. SnowLucas macrumors member

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    Feb 19, 2015
    #24
    Does the file have an HD audio track like Dolby TrueHD or DTSHD? From a quick look around some forums the Xbox one plex client always has to transcode with these. So it might not be the video file that's the issue (HEVC 4K does seem to be supported by the Xbox one s in plex) but the audio that comes with it.

    Personally having a quick look at those kinds of issues I would avoid using an Xbox one as a plex client if I was determined to watch 4K content. Actually I think audio is more important than the jump from 1080p to 4K so again the Xbox one fails for me compared to lots of other devices which can play HD audio without transcoding.
     
  25. c613m thread starter macrumors 6502

    c613m

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    #25
    Even if I need to re-encode the files I'm unsure how to do that and still retain the 4K resolution, as all problems would be solved this way given that my TV can handle the HVEC files.

    Oh and my iMac is serving as the Plex Server, everything else connected to it are clients.
     

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