[FFmpeg-user] how to change the framerate for an MTS file recorded by the Panasonic TM-700 in 60p?

[Christian von Kutzleben]

> 
>> I could image, that for this particular conversion, 
>> assuming an example sequence of i1p1p2p3p4...
>> the conversion could yield i1(p1+p2)(p3+p4), which, 
>> give or take rounding issues, would be virtually lossless.
> 
> I do not understand this, but -r simply drops (or duplicates) 
> frames, I believe the ffmpeg console output tells you more.
> (If not, you are most probably using a severely broken 
> version of FFmpeg.)

It did indeed drop frames and worked as expected. 

I was referring to a lower level: how the frames are encoded. If it were all I-frames, every other could simply be dropped and no recoding would be needed. If it were frames containing only deltas to the previous frames, two delta frames could be added to a new single delta frame, and one could argue, that ((I + p1) + p2) is equivalent to (I + (p1+p2)) with p_new := p1 + p2

This would allow a frame rate reduction by factor 2 without recoding.

Of course the stream might be much more complicated, other frame types, some I- frames on even, some on odd positions, ...

Christian