[Libav-user] how to predict the size of destination clips

[Carl Eugen Hoyos]

qw <applemax82 at ...> writes:

> Hi,Does ffmpeg provide some function that can predict 
> the size of destination clips before transcoding?

How would that work? (in theory)

Either you did set an (average) bitrate when starting the 
encoder, then you know which value you chose and if you 
also know the length of the input, you can calculate the 
size of the output file.
FFmpeg generally cannot know the length of the input.
If you did not set a bitrate (but constant quality) then 
it is impossible to calculate the output file size.

Carl Eugen