How to lower the FPS for a MKV file?

[sldvd]

I have a MKV file that is over 6 GB, and I want to shrink it so that it fits on a single DVD. It is 60 fps, and if I were to somehow lower the fps to 30, then I'm pretty sure it will be under 4.7 GB. Can anyone recommend a Windows program (preferably freeware) that can do that?

[Ai Haibara]

You might try experimenting with splitMKV or uncropMKV, instead.

[sldvd]

splitMKV doesn't support that, and I tried uncropMKV and it didn't work (and I contacted the author and he told me it wouldn't work).

[Ai Haibara]

No, not lowering the FPS. I meant you could use splitMKV to split the MKV into separate files rather than reduce the quality, or use uncropMKV's methods of shrinking the MKV instead of reducing the FPS.

[mail2tom]

Is this video interlaced? HD h264 captures from my Hauppauge 1212 have a frame-rate of 59.940 but are interlaced with an original frame-rate of 29.970. The bit-rate of the video can be varied, but the frame-rate stays the same (as the source). I make my videos smaller by changing the capture bit-rate, or after the fact by re-encoding to a lower bit-rate.

[sldvd]

I'm not sure if it is interlaced. What software do you use? This uncropMKV software seems a little too advanced for me, as I can't get it to do anything. I have no experience with editing videos.

[jagabo]

The fps makes no direct difference in the file size.

file size = bitrate * running time

Lower frame rates may require less bitrate to maintain quality but if your 60 fps video is film based it has many duplicate frames -- which require hardly any bitrate. Removing all the duplicates won't give you a video that compresses much better. Even if it's true 60 fps (where every frame is different) reducing the frame rate in half won't reduce the required bitrate by half because now the changes from frame to frame are twice as big -- thereby requiring more bitrate (not more than the original video, but more than half the originals' bitrate). Starting with a high quality 60 fps source and creating 6 GB 60 fps file and a 4 GB 30 fps file might give roughly the same quality (except the 30 fps file will be obviously more jerky on TV), but decimating and recompressing the 60 fps file will introduce another round of artifacts.