Jerky interleaved video after encoding M2TS file with VirtualDub

[GD314]

Hi

I have a .m2ts file containing an interlaced AVC stream. After cutting parts, I convert it using x264vfw codec, with --tff option. The problem is the result is slightly jerky : every one second or so, there's a little jerk visible on slow regular moves.
The frame rate is left untouched (25FPS).
The Display Renderer Statistics menu (ctrl + j) of MPC-HC says "1 frame drop every 0.50 seconds".

What could be the reason?

Thanks for your help.

[jagabo]

There are probably dozens of possible reasons. You need to provide a sample of your source (not reencoded) and an encoded video made from that source.

[GD314]

Hello

I cropped 10s of the original video using tsMuxeR GUI to provide you with a short extract. I encoded it using the same settings I used for the whole video. And then, surprise : no more jerks. Then I tried the same with the whole video remuxed : still no jerks.
It seems the remux step fixes something wrong in the original video, and finally this is no surprise as the video is a digital TV recording.
I always remux the M2TS file to MKV before using VirtualDub (as some M2TS frames have a problem when displayed within VirtualDub), but this MKV remux step doesn't prevent the jerks.

So I didn't find the reason of the original bug, but a way to circumvent it.
Thank you!

[jagabo]

Whatever works!