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bashaudioffmpegyoutube-dl

Inconsistent behaviour of ffmpeg -i flag

I'm trying to write a Bash script that would download an audio track from youtube and convert it to Apple ringtone format, which is .m4r. The tools I employ are youtube-dl and ffmpeg. The former seems to work fine but I have a strange issue with the latter. When I try to pass the name of the file parametrically, shell prints that file or directory can't be found.enter image description here

I use the same method for unwraping user input (or my defaults) for both commands but it only seems to work with youtube-dl.

Example of what doesn't work and print the text above. Obviously, all the files are in fact there and accessible

youtube-dl -i --extract-audio --audio-format m4a -o $filepath_interim  --audio-quality 0 $video_link
ffmpeg -i $filepath_interim -acodec copy -f ipod -ss $offset  -t $length $filepath_out

So, I tried to do it with '' strings, $(command) syntax, it all failed. I only found one way to make it work, which is to hard code the values of the paths but this defeats the whole purpose of my script.

youtube-dl -i --extract-audio --audio-format m4a -o $filepath_interim  --audio-quality 0 $video_link
ffmpeg -i ~/Downloads/ringtone.m4a -acodec copy -f ipod -ss $offset  -t $length ~/Downloads/ringtone.m4r

I want to figure out why this keeps happening, whether it is in any way specific to ffmpeg or am I just missing some piece of knowledge about $ name unwrapping.

Minimal Working Example. Run with bash or pack in script and run. If your path to bash is different, please change the shebang:

#!/usr/local/bin/bash
# initialise
filepath_interim="~/Downloads/ringtone.m4a"
filepath_out="~/Downloads/ringtone.m4r"
video_link="https://www.youtube.com/watch?v=dQw4w9WgXcQ"
offset=0
length=30

# main part
youtube-dl -i --extract-audio --audio-format m4a -o $filepath_interim  --audio-quality 0 $video_link
ffmpeg -i $filepath_interim -acodec copy -f ipod -ss $offset  -t $length $filepath_out
Solution

  • Change ~ to $HOME

    See ShellCheck and SC2088: Tilde (~) does not expand in quotes, use $HOME for more info.