How to fix -wmv to mp4 conversion jerky

[avilon]

When trying to convert 2.7Gb 30 minutes wmv file to smaller mp4, playback with VLC palyer is significantly jerky. Like frames missing or something.

Source is: Video, ID2, Windows Media video 9 (WMV3), resolution 1280x736, display resolution 1280x720, Frame rate 29.970179, Decoded format Planar 4:2:0 YUV
Target x265 and mp3.

Probably source is also a little bit jerky but still viewable with vlc player without complaints.
How to troubeshoot?

[eumagga0x2a]

Could you please provide admlog.txt located in %localappdata%\avidemux from just loading the source video?

Avidemux tries to compute sane PTS (presentation timestamps) for videos encoded with some legacy codecs including WMV3 based on frame flags (I/P/B). If flags are wrong (e.g. B-frames are not flagged as B-frames), the whole falls apart. A solution for this particular file could be to resort to the function used by Avidemux to restore correct picture display order by decoding the entire video like when loading a H.264 muxed into a container not supporting presentation timestamps (e.g. AVI). I don't remember now why I decided not to go this way (either it didn't work out or it broke some other edge cases).

The problem is that you need to be able to build Avidemux from source to try this out, i.e. you need a Linux system.