Put together a .blend file and then animated it using FFMPEG output selection. After watching the mpeg, I decided I wanted to slow the animation down by half. However, it appears that if I change the default 24 fps to 12 fps… the animation rendering errors out. It appears that you cannot just modify the frame rate when using FFMPEG…
Is this a bug or is this fundamentally not valid to try and do ? I’m really hoping that
I am just doing something incorrectly. If not, do I have other options ?
I’m pretty sure that when you set frame rate to 12 fps, it does exactly that, maintains the total vid length and combines frames to give you 12fps. You need to set time to twice as long also
you can call it a bug,
but some codecs are normaly limited to special fps-rates.
Thats why some programms may try not to do what you want.
For example the mpeg2-format, thats used for dvd, should not allow a fps-rate of 12 frames per second … and so on.
If you have to use such a codec, you have to double the frames and have the fps-rate at the old rate.
ffmpeg will normaly try to keep the video in sync to its time-stamps even if you change the fps-rate (this is, ffmpeg will add or drop frames to keep the timing).
One way is to write a video out as single frames and encode these frames with a different fps-rate.
(maybe there are tools to do this on-the-fly, like a pipe in the decoding/encoding action)
I doubt it’s bug, and you can change the frame rate when using FFMPEG, but it may not work well if it goes outside some reasonable parameters. 12fps isn’t very reasonable.
12fps is an extremely low frame rate, and your animation will tend to look very jerky, like badly done stop-motion. This is because the individual frames are being displayed for so long they aren’t perceived well as a continuous action when seen in sequence. This is due to a lower limit on the human persistence of vision effect, which makes movies possible.
Rule of thumb is that around 15fps is the bare minimum frame rate before things start looking like extremely bad game lag Old silent movies were shot at around 18fps; the modern film frame rate is 24fps; video standards vary but are all well above the film standard.
So to slow your motion properly, you need to modify the animation to produce more frames for the same actions, as has been suggested. This can be done a couple of ways depending on the nature of your animation – you can manually scale all your keyframes, or (in 2.49b, at least) use a Time IPO.
Old silent movies were shot at around 18fps; the modern film frame rate is 24fps; video standards vary but are all well above the film standard.