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Muxing x265 encoded MP4 video file results in massive frame loss

Software used:

  • Windows 10 (Updated)
  • MKVToolNix v44.0.0 (64-bit)
  • VLC media player 3.0.8

It seems MKVToolNix has issues muxing x265 encoded files, resulting in a very jittery, lagging video file, missing lots of frames.

I've two MP4-files of the same movie (see pics) and a SRT-file. One of the MP4-files is x264 encoded. The other is x265 encoded.

pic01

Playing both files with VLC media player for a minute, shows zero frame loss.

pic02 pic04

After having muxed the SRT-file to both MP4-files, VLC media player shows:

pic03 pic05

I also put the x265 encoded MP4-file through MKVToolNix without a SRT-file, resulting again in massive frame loss.

pic06

It's obvious something's going wrong. But why or what is beyond my knowledge.

I've also used ffmpeg and this also resulted in massive frame loss as well, until I used the libx265 parameter, but this takes not mere minutes, like MKVToolNix, but literally hours.

Hopefully this issue will be resolved quick, since more and more x265 files are populating the internet.

Edited by Moritz Bunkus