FPS setting in muxer options

[sark]

Is it possible to add an option to enable a muxer fps adjustment that would enable slow motion output without reencoding.
ffmpeg can do this, but creates content with monotonic dts issues. These can be fixed by Avidemux without reencoding, so it seems plausable that Avidemux could be capable of outputting fps muxer adjusted content without the issue?

[eumagga0x2a]

A disagreement between FPS specified via codec extradata and via container-level timestamps, especially in case of H.264, would perfectly derail Avidemux as Avidemux believes extradata, not container. Thus the only feature which I consider as nice-to-have would be an ability to easily discard container-level PTS and DTS, replacing them with timestamps derived from codec time base – plenty of files with container-level timestamps suggesting variable FPS are essitially CFR videos with timestamps being an approximation due to unsuitable time base. In all other cases, such a mode would destroy A/V sync.

[sark]

My use of the word muxer was misleading. I should have refered to the Output Format options.
I was thinking a framerate option here could affect both container and video stream data. As is possible with tsMuxeR.

Although Avidemux could slow down the audio (with encoding) to match the video duration, it's more likely that slow motion output would not be using the original recorded audio. Hence syncing would not be an issue.

Just a thought