[FFmpeg-user] filter for changing frame rate

[Daniel Oberhoff]

> On 13 May 2019, at 13:40, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> 
> Am Mo., 13. Mai 2019 um 13:36 Uhr schrieb Daniel Oberhoff via
> ffmpeg-user <ffmpeg-user at ffmpeg.org>:
>> 
>> 
>>> 
>>> You can not.
>> 
>> I am curious what exactly the hindrance is. As I understand at least mp4 there is not really a concept of frame rate in the file and in theory every frame can have a different „rate“, defined solely by pts.
> 
> FFmpeg's mp4 muxer does not support variable frame rate.

Oh, how so? From what I understand about mp4 it does not even contain frame rate in the metadata. For us this effectively means we cannot use mp4, since some of our sources are not very stable in their frame timing.
So does the muxer ignore the incoming frame pts and just imprint monotonic pts with the given frame rate?