I got some issues when I accessed PMS via application (not web-based)
if i checked “Disable video stream transcoding” on PMS then “plex application (likes android app)” can’t play any multimedia. (but, it’s worked via webui, normally)
In all seriousness, if the video is transcoding, it is usually due to (a) an incompatibility with the Plex client, or (b) a bandwidth or other such limit on the server or the client. There can be other reasons as well.
To determine why it is transcoding requires additional information.
What version of Plex Media Server & what platform (Win/Linux/Mac/etc)?
What version of the Android client and what platform (phone, TV, FireStick, etc)?
See https://app.plex.tv/desktop#!/settings/devices/all
Check the settings on the Android app. Verify the following:
Automatically adjust quality = off
Home streaming = maximum/original
Remote streaming = maximum/original
With no other server activity (users streaming, adding media, etc), play the problematic video, with subtitles off, on the Android app. Monitor playback with Plex Dashboard → Now Playing. Toggle the button on the top-right to expand the playback information if necessary.
What does it show?
Is the connection local/remote/indirect?
Are the video and audio streams direct playing/direct streaming/transcoding?
Include a screenshot if possible.
If still transcoding, then stop playback, wait two minutes, and pull the log files. Attach the entire ZIP file to the thread (just drag it into the compose window). See the “Reporting Issues…” article for details on log retrieval.