[FFmpeg-user] Zoom effect

[Carl Eugen Hoyos]

Paulo Barretto <pmbarretto <at> gmail.com> writes:

> I mean a filter with time-dependent width and height 
> parameters, that would scale the image in each frame 
> to a different size, then crop 

Cropping first and then scaling seems more 
realistic to me since the crop filter already 
supports timestamps.

Unfortunately, only the offset is currently allowed to 
change over time (not the cropping size), I am not 
sure if this was just an oversight or if there is a 
fundamental problem (I think changing framesize in 
the filterchain is supported, it is supported in the 
decoder at least).

To quote the documentation:
"[width] is evaluated only once during the filter 
configuration."

Perhaps one of the filter gurus can comment what 
the underlying problem is.

Carl Eugen