January 2020

  FFmpeg concat videos without reencoding
January 12   |   Terminal

To concatenate some videos using ffmpeg we need to provide a text file with the word file followed by the path to the media:



# We can use absolute or relative paths

file '/path/to/video1.mp4'
file '/path/to/video2.mp4'
file '/path/to/video3.mp4'



# If you use an absolute path to the file we need to add the parameter -safe 0
ffmpeg -f concat -safe 0 -i videolist.txt -c copy output.mp4

 The following scripts will allow us to automate the creation of the text file


# Windows
(for %i in (\*.mp4) do @echo file '%i') > videolist.txt
ffmpeg -f concat -i videolist.txt -c copy output.mp4

# Bash
for f in ./\*.mp4; do echo "file '\$f'" >> videolist.txt; done
ffmpeg -f concat -i videolist.txt -c copy output.mp4

# Zsh - Using Zsh we can run the command in one single line
ffmpeg -f concat -safe 0 -i <(for f in ./\*.mp4; do echo "file '$PWD/$f'"; done) -c copy output.mp4

Sometimes would be useful to repeat the same video n times, use the following scripts

 Repeat same video


# Windows ... in (start,step,end)
(for /l %i in (1,1,10) do @echo file './videoloop.mp4') > mylist.txt
ffmpeg -f concat -i list.txt -c copy output.mp4

# Bash
for i in {1..4}; do printf "file '%s'\n" input.mp4 >> list.txt; done
ffmpeg -f concat -i list.txt -c copy output.mp4


  Terminal check if string has value
January 5   |   Terminal

A basic task when you are scripting is to verify if a string is empty or not. We can do it using the following operators -n y -z

 Check if empty



if [[ -z $VAR ]]; then
echo "String is empty."

 Check if not empty



if [[ -n $VAR ]]; then
echo "String is not empty."