Change FPS video filter not changing total length of video

[Lyapunov]

I'm new to using the program, so it's very possible that I'm not using the correct settings.

I have been leaving the Video and Audio Output as Copy, and using the MP4 Muxer as the output format (since .mp4 is the source video format).

For the filter, I have been leaving the Source Fps at 25, and have been changing the Destination Fps to 29.8

The preview button shows the correct modified length of 1 hour and 2 minutes. The original video length is 1 hour and 14 minutes and that is what is still displayed after I check on "Play filtered".

I did this to fix an issue with the audio being too sped up, and strangely enough when I hit play the audio and video is synchronized for the beginning.

I am using this program on Windows 7 64-bit if that is relevant.

[Jan Gruuthuse]

I have been leaving the Video and Audio Output as Copy, and using the MP4 Muxer as the output format (since .mp4 is the source video format).

That is not a requirement, you could use any container format  mp4, mkv, ... (.avi is not recommended for h264)

For the filter, I have been leaving the Source Fps at 25, and have been changing the Destination Fps to 29.8

When applying filter, re-encoding is required (no copy)