https://bugs.freedesktop.org/show_bug.cgi?id=98005
--- Comment #15 from Andy Furniss adf.lists@gmail.com --- (In reply to Boyuan Zhang from comment #13)
In the meantime, I will look at the ntsc framerate.
On this I looked what gstreamer and avconv were sending and both do send the denominator so a v2 (horrible looking) patch attached which tests OK for a variety of inputs.
I guess there's a more elegant way, but it works. Maybe over paranoid trying to avoid division by 0 in this case, but I notice that the gop patch can get one if the user asks for -g 0 with avconv.