Recorded MKV Files Less than Satisfactory

[Kaldelar]

I should get points for how political I sound... Anyway.

I have these .mkv files, gorgeous quality in both audio and video, and thought I'd make a separate video using several parts of them. So, using the old Record trick (because splitting or even loading an mkv in avidemux is a nightmare) and has always given good results (never tried on an mkv before, obviously) - mp4, avi, wmv, you name it. But today, not so good results. Three things:
The segment I want recorded is the time period between 40:52 and 41:32 (total 40 seconds), however the generated recording is only 33 seconds and starts at 41:00, despite me pressing the record button way earlier than that. I have tried pausing the video and then pressing record, but with the same results.
The video isn't choppy, but there is a slight... how shall I put it... loss of fluidity in the recorded pieces. Audio is still on track and synched with lips/effects, but it's there, subtle and irritating.
Lastly, it generates them as .mp4 files. Don't know if that's always the deal, but I thought VLC gave recorded pieces the same extension as the original source.

Is there an inherent problem with recording .mkv files or is it some setting that needs adjusting?

VLC version is 2.0.1, OS: WinXp.

[Lotesdelere]

I think it starts to record at the next keyframe, the reason why you lose some part.
The video streams used in MKV are usually H.264/AVC ones, which may be quite complicated nowadays, with many B-frames used as reference and this is not easy to deal with, compared to other formats like MPEG-4 ASP (Xvid, DivX) or WMV.
What you're looking for is a video editor and VLC is not one.

[Kaldelar]

Oh, yes, that makes sense. Suppose that's why it produces the same clip even if I start the recording earlier... Right, thanks.

[Jean-Baptiste Kempf]

Recording mkv is not good yet with VLC. Try a 2.1 nightly build, it might be better.