input plugin: custom commands

[hhirtz]

Idea: allow users to define custom commands as input plugins, e.g. with this configuration

input_command {
        scheme "http"
        scheme "https"
        command "yt-dlp"
}

and this input:

mpc add https://www.youtube.com/watch?v=DON5WvSVYSc

mpd would spawn yt-dlp with the URL as first argument, or something, and read the audio from its standard output (the curl input plugin would have a lower priority for this example to work.. or be disabled completely in the configuration).

This could be an easier way to support the following ideas, without adding more lines of code to this project:

• youtube plugin youtube-dl plugin #223 youtube-dl input/playlist plugin #955
• qobuz plugin Qobuz input plugin is not working #1209
• tidal plugin Tidal plugin not playing albums #627
• youtube-dl and yt-dlp have a retry mechanism already curl input plugin retry mechanism #431
• ... and other things, maybe.. haven't looked much at the issue tracker

I'm willing to implement such plugin, and wanted to know your thoughts about this before digging into the code base. 😃

[MaxKellermann]

If you believe the feature is useful (I don't need it), and if you do it properly, I'll merge it. Beware, there are lots of complexities in what looks simple at first:

• will you support seeking?
• will you support indicating the total size?
• will you support indicating the MIME type?
• will you support tags?
• how do you propagate error conditions between the child process and MPD?
• will you support Windows?
• spawning child processe from MPD is difficult; there are things like the signal block mask that need to be considered. I can help with that part.

[hhirtz]

Thanks for the quick reply. I'll look into these points and come back when I have something to show.