Could someone help me in providing a solution for the problem that I am facing? When I try to watch any H264 videos remotely the videos just keep buffering, I have connected my Plex server on NAS EX4100 WD with internet speed 260 MB/s. Also, I have kept the option on Plex “Background transcoding x264 preset” to ultra-fast to help me in buffering, however, I am still facing a buffer problem.
Any help, please 
Is that 260 Mbps your internet upload or download speed? If it’s the download speed… what’s the upload speed you get from your ISP?
In addition… can you double-check the Now Playing section of the Dashboard in Plex Web to confirm how the media is transferred (remote vs. indirect) and if/how it’s being transcoded. Maybe you can attach a screenshot of that tile.
please note that some series works flawlessly. However, some series keeps buffering; this only outside my home network. in the same network all videos runs perfectly
Looks like that particular video is transcoding heavily (near 100% CPU consumption).
Could you for completeness provide the screenshot of the particular ´now playing element. In particular:
It looks like that’s not actually a h264 video but h265/HEVC.
The WD cannot hw-transcode that format, so it’ll do it all with its CPU which appears not to be strong enough to do that in real-time.
You could try to set the playback quality to “original” or “max” on your iPhone to avoid the transcoding (in Plex for iOS on your iPhone: Settings > Quality > Remote Streaming). That might work if you’re mobile bandwidth and/or data plan don’t get in the way 
Edit:
not really changing the statement above… the EX4100 has no support for hw-transcoding at all (that’s the MyCloud Home and MyCloud Pro models). Nonetheless… transcoding h265/HEVC is too much for that NAS
Still the same …
So what is the best type of videos i need to look for. I am sorry for these kinds of questions, I am new in this field
Or how do I know which type of videos suits my NAS
The simple answer are the ones that don’t transcode
How do I know that, is there any way I can know that before downloading a video/movie?
Safe bet is mp4, but they can have pitfalls with embedded metadata. I use mkv mostly
One of the series that i am facing a problem in buffering is .mkv
does the size matter of the video matter?
SE56’s post was a little misleading…
MP4 (or M4V) as a file container will be the most compatible.
What’s more critical is what is inside that container.
In your case that’s a h264 video with aac audio. Those codecs are among the most safe ones with todays players. The bitrate could be a limiting factor that can cause Plex to decrease the quality.
If the file content is ok to play in the client without transcoding, Plex will be able to “re-mux” the files – meaning it’ll just put the content in a different container on-the-fly.
To determine what is causing the buffering we’d need to dig into your logs.
please if you can help i will share with you the log. I just want to understand the types of videos that support my NAS
Or how i can convert the videos to have the same quality and it can work on my NAS? i think this way it will be easier for me to do
Mind sharing those logs?
The Plex app on iOS should actually play a lot natively and directly without transcoding if you…
Settings > Quality > Remote streaming (see above)Settings > Advanced > Allow Direct Play (should be checked)Settings > Advanced > Use old player (should be disabled)Settings > Advanced > Subtitles > Burn subtitles (should be set to automatic)Settings > [Server Name] > Remote Access > Internet upload speed
Settings > [Server Name] > Remote Access > Limit remote stream bitrate
Settings > [Server Name] > Network > Remote streams allowed per user (should only impact your playback if you play videos from multiple clients simultaneously)
Settings > [Server Name] > Transcoder > Maximum simultaneous transcodes (should only impact your playback if you play videos from multiple clients simultaneously)
From the screenshot above this video should play ok.
