Can Plex play MP4? Certainly it can. But it happens that you might encounter situations like Plex not recognizing MP4 or Plex not playing MP4. If you face such Plex MP4 issues, read this article to understand the possible causes and get the solution to fix the problem handily!

Michelle | Dec 18, 2020
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  • Causes and Solutions to Plex Not Detecting MP4
  • Causes and Solutions to Plex Not Playing MP4
  • Causes and Solutions to Plex Not Detecting MP4

    Cause 1. The most likely cause of your Plex not recognizing MP4 is that you have inappropriately named your media file.

    Plex has standard naming conventions for both the movie and TV series. For movies, the basic naming convention should be like this: MovieName (release year).ext → e.g. Avatar (2009).mkv; And the TV series/shows should be named in the following order: Season-based: ShowName – SXXEXX – Optional_Info.ext → e.g. The Flash - s01e01.mp4, Time-based: ShowName – YYYY-MM-DD – Optional_Info.ext → e.g. The Colbert Report - 2011-11-15.avi.

    *.ext means the container format, such as .mp4, .mkv, etc.
    *For TV series, it is suggested to name the season and episode as s01e01 instead of s1e1.

    Cause 2. Another possible cause might come from the confusing metadata of the MP4 files.

    MP4 carries metadata like the title, tags, genre, publisher, etc. of the content. If the metadata information is incomplete or contradictory to the file name, the Plex Media Server will misidentify or not recognize the file.

    Solution: Optimize the File Name and Update the Library

    First, check whether your media files are named in the right way and correct it if there’s something wrong. If necessary, edit the metadata of your MP4 files by right-clicking on the file → PropertiesDetails.

    Then work the Plex Dance to remove all cached metadata and XML data for the relevant library. The specific steps:

    1. Move all the media files out of the library source folder
    2. Click the Actions (three-dot) of the relevant library → Scan Library Files to detect changes
    3. Click the Actions (three-dot) of the relevant library → Manage Library → Empty Trash
    4. Go to the server, click on More Actions (three-dot) → Manage Server → Clean Bundles
    5. Double-check the file names and move files back to the source folder
    6. Click the Actions (three-dot) of the relevant library → Scan Library Files to update

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    Causes and Solutions to Plex Not Playing MP4

    This issue is complicated as it involves two devices, the device where the Plex Media Server is set up and the device where the Plex app is installed. Before we delve deeper, we first have to understand the way how Plex streams your media files to the client device to get an insight into the possible causes of this problem later.

    Plex has three streaming modes, namely, Direct Play, Direct Stream, and Transcoding.

    Direct Play means when the source media is compatible with the client device’s playback capabilities regarding the file container, video/audio codecs, the bitrate, and the resolution, it can be direct played on the client device with no transcoding and no CPU-consuming of the server device.

    Direct Stream means when the source media is in a format container that is not compatible with the client device, it will be repackaged into a compatible container and then be direct streamed to the client device. It requires a little processing power of the server device.

    Transcoding means when the source media is incompatible with the client device or it has soft subtitles included, it must be fully transcoded to a compatible format that can be played on the client device. This is a CPU-intensive process to the server device.

    After explaining the three streaming modes, you might’ve noticed that the media streaming performance is tied to the media file itself, the compatibility of the client device, and the capacity of the server device. Put another way, any media file that can be direct played or direct streamed should have a smooth streaming process. And any media file that needs to be transcoded has a varying streaming performance depending on the power of the server device. If it is a low-end server device such as the NAS, it might not support real-time transcoding, and you are likely to receive the Plex not playing your media error.

    So here are the probable causes for your Plex not playing MP4:

    1. Your MP4 is compatible with your client device, but you’ve disabled the Direct Play and Direct Steam on your Plex app and your server device is too lower-powered to do the transcoding.

    2. Your MP4 is incompatible with your client device, and your server device is too lower-powered to do the transcoding.

    Solution: Enable the Direct Play and Direct Stream, and Avoid Plex Transcoding

    You can enable the Direct Play and Direct Stream within the settings of your Plex app.

    To try to avoid Plex transcoding your MP4 files, you should have the file matching the Plex MP4 supported specs that can usually be direct played (for a better result, you can also look to your client’s playback capacity). See the best Plex supported formats below:

    Container: MP4
    Resolution: 1920x1080 or lower
    Video Codec: H.264
    Audio Codec: AAC (2 channels)
    Frame Rate: 30 fps
    Bit Rate: 20 Mbps or lower

    Check whether your MP4 file meets the above requirements and convert it to fit the specs with a third-party video converter.

    Here is how:

    We are going to use a software called WonderFox DVD Video Converter. This is all-in-one software to convert videos, download movies, and even rip DVDs. And it supports tweaking the parameters, such as changing the resolution, checking the video/audio codecs, converting the frame rate, and adjusting the bit rate.

    Before start, please free download free download the software and install it on your PC.

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    Step 1. Import the MP4

    Launch WonderFox DVD Video Converter. On the upper left, click Add Files to import or directly drag and drop the MP4 file into this program.

    Step 2. Change Settings

    Click on the format icon to select MP4 under the Video tab. Then open the Settings on the lower right, change the parameters to match the Plex MP4 specs showing above. Then click OK.

    Step 3. Start Conversion

    Click Run to start conversion.


    That’s all for how to fix the Plex MP4 related issues. If you have any other doubts, please feel free to reach me at any time. Thanks for reading!

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