Can't seek/cut MXF videos precisely, and some audio renders out of sync?

Hi everyone, Kdenlive is working great for me except for a problem cutting MXF videos from my Canon XF100, and an audio sync issue when I try to work around the cutting problem with MTS proxies. Does anyone have any ideas for workarounds? Are these known issues, or should I file bug reports?

The first problem is that, although the MXF videos play back fine (Kdenlive identifies them as MPEG-2 yuv422p video at 23.976024 fps with PCM signed 16-bit little endian audio at 48000 Hz), they will not seek more precisely than a 1-second block. What I mean is that if what I'm calling a "block" starts at 22 seconds and 12 frames, I will not be able to seek or cut to anything between 22:12 and 23:12. If I try to seek to, say, 22:20 or 23:06, it will always start playing from 22:12. If I seek to the next second (23:12), however, it will play from there but, likewise, if I try to seek to anything between 23:12 and 24:12, it will only play from 23:12. This makes it impossible to make precise cuts of audio or video. In looking into it, I've found that the first 12 frames of any video seem to form their own block but, after that, every block is one second (so, 0 to 0:12, 0:12 to 1:12, 1:12 to 2:12, etc.).

To work around this, I generated proxies using the standard MPEG encoding profile included with Kdenlive. With those, I can seek with frame precision. However, when I render the final video, the MXF seeking issue rears its head again, and all the cuts are off (or those that are supposed to happen within one of "blocks," anyway).

Because I invested so much time into the edit, however, I decided I would render from the proxies instead of the originals, as that seemed to work in my tests. Unfortunately, when I rendered the full video, this raised what I guess is a different issue: the audio goes out of sync in places. This also occurs when playing back the timeline in Kdenlive from before the point of the desync. If, however, I start playback from after the point where the audio goes out of sync, it plays back correctly. I've written "sync" too many times now, but does that make sense?

I have tested these issues both with Kdenlive 0.9.2 and MLT 0.8.0 and also with Kdenlive 0.9.3+git20120815.72a8dbe8 and MLT 0.8.1+git20120817.99d95a01, all as packages from the Sunab Ubuntu repository. I am running Ubuntu 12.04.

Thanks in advance for any suggestions.