mkv to Blu ray gives wrong aspect ratio

[Dragonsf]

I have a mkv file, which is 1920x816 (AR2.35:1).
When I try to convert it to BD, PowerDVD plays it in full screen mode (16:9). Everything looks stretched vertically of course.
Is there a fats way, to change the AR? I tried to reconvert with MP4Box/yamb/mkvmergeGui etc, but always with the same result.
I'm now trying to reconvert with Handbrake, but this takes very long. Please advise, how to accomplish this.

[Baldrick]

Have you tried multiAVCHD? and maybe you need to use uncropmkv.

[Dragonsf]

Thanks for the advice. But uncropmkv seems to do nothing (because the mkv file was not changed at all).Am I missing something?

[poisondeathray]

You need to add the borders back to make it full frame 1920x1080 like the original blu-ray. This requires re-encoding

(1080-816)/2 = 132 pixels to the top and bottom

[Dragonsf]

Yes, I understand that now. I hoped, there was a shortcut, as handbrake took about 5 hours to convert a 2.5h movie.
I eventually got uncropmkv running (reinstalled Avisynth), but PowerDVD doesn't recognize the BD disk I created with MulitAVCHD.
I think, it has some to do with the sound track, as the first BD (done with Handbrake) has no sound at all.
I keep on trying. Thanks anyway for the valuable advice.

[Dragonsf]

Eventually I got things working.
Trouble was, that after changing my graphic card from ATI to NVIDIA, some ATI codecs still remained on my machine. After removing them in the registry and filter settings. Everything works fine now.
BTW, ARCSoft MediaTheatre is much better in dealing with Blu Ray material than PowerDVD.

[Wolfen]

You can try to change the (MKV) files display size info with header editor (so it displays that AR when the movie plays)in MKMerge it's in the file menu.