How to use variables in ffmpy (python wrapper for FFmpeg)?

Question

I would like to ask how to use variables in ffmpy (Python wrapper for FFmpeg).

To be exactly: I want to use variables to crop video. The FFmpeg command is:

ffmpeg in.mp4 -filter:v "crop=out_w:out_h:x:y" out.mp4

https://ffmpeg.org/ffmpeg-filters.html#crop

To use it in Python/ffmpy, I wrote these codes:

from ffmpy import FFmpeg
import ffmpy

# define the variables
out_w = 100
out_h = 120
x = 50
y = 80

inputFile = "F:\\in.avi"
outputFile = "F:\\out.avi"

ff = FFmpeg(inputs = {inputFile: None}, outputs= {outputFile: " -y -filter:v `crop=100:120:50:80'"}) 
#This line works fine.

#Now rewrite the above line using variables...
ff = FFmpeg(inputs = {inputFile: None}, outputs={outputFile: " -y -filter:v `crop=out_w:out_h:x:y'"} ) 
#...It line does not work. I guess it is wrong to use variables in the statement.
#...This is my question. How to write this line using variables? 

ff.cmd
ff.run()

Thanks for your help!

rgettman · Accepted Answer · 2018-05-01 19:25:38Z

1

I can solve your problem:

Recently I am trying to run this command:

ff = ffmpy.FFmpeg(inputs={inputs: None}, outputs={output: '-ss 0:1:0 -t 0:2:0 -c copy'})

It's perfectly running. But from the user's point of view, the inputs should given by them.

So I modified the command a little bit.

ff = ffmpy.FFmpeg(inputs={input: None}, outputs={output: '-ss %d:%d:%d -t %d:%d:%d -c copy' % (start_hour,start_min,start_sec,end_hour,end_min,end_sec)})

I simply use %d to use variables (int) in my command and it runs perfectly! I hope this helps.

edited May 1, 2018 at 19:25

rgettman

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answered May 1, 2018 at 19:06

Yash Jain

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Brian Boynton · Accepted Answer · 2020-03-11 21:36:37Z

1

Late answer but this might help others.

f-strings solved this for me. This works in python 3.6 or above.

import ffmpy

# define the variables
out_w = 100
out_h = 100
x = 50
y = 80

#set file locations
inputFile = "F:\\in.avi"
outputFile = "F:\\out.avi"

ff = ffmpy.FFmpeg(
    inputs = {inputFile : None},

    outputs = {outputFile :  f" -y -filter:v crop={out_w}:{out_h}:{x}:{y}" }    
) 
print(ff.cmd) #optional
ff.cmd
ff.run()

The "f" in the output line tells python to use f-strings and replace with the variables you defined above.

answered Mar 11, 2020 at 21:36

Brian Boynton

111 bronze badge

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