extract_audio.sf

#!/usr/bin/ruby

# Daniel "Trizen" Șuteu
# Date: 21 March 2020
# Edit: 24 October 2023
# https://github.com/trizen

# Extract audio from video files with ffmpeg, using `n` parallel processes.

func ffmpeg_convert(input, output) {
    Sys.run("ffmpeg", "-loglevel", "warning", "-i", input, "-vn", "-sn", "-dn", "-c:a", "copy", output)
}

func prepare_file(file, outdir, ext) {

    var out = ""

    if (file =~ /^(.*)\.\w+\z/s) {|m|
        out = (m[0] + "." + ext)
    }
    else {
        out = (file + "." + ext)
    }

    out = File(outdir, File(out).basename)

    if (File(out).rel2abs == File(file).rel2abs) {
        return nil
    }

    return out
}

var threads = 2
var format  = 'opus'
var outdir  = Dir.cwd
var delete_original = false

func print_help(exit_code=0) {

    var name = File(__FILE__).basename

    print <<"EOT"
usage: #{name} [options] [files]

options:
    -f  --format=s  : output format (default: #{format})
    -d  --delete!   : delete the original files (default: #{delete_original})
    -o  --outdir=s  : output directory (default: .)
    -t  --threads=i : number of threads to use (default: #{threads})

example:
    #{name} -f opus -t 4 *.webm    # extract OPUS audio from WEBM videos
EOT

    Sys.exit(exit_code)
}

ARGV.getopt!(
    'f|format=s'  => \format,
    't|threads=i' => \threads,
    'o|outdir=s'  => \outdir,
    'd|delete!'   => \delete_original,
    'h|help'      => print_help,
)

outdir.exists || outdir.make_path || die "Can't create directory <<#{outdir}>>: #{$!}"

ARGV || print_help(1)

ARGV.each_slice(threads, {|*slice|

    var files = slice.grep { File(_).exists }

    var conversions = files.map {|file|
        [File(file), prepare_file(file, outdir, format)]
    }.grep {
        defined(.tail)
    }.grep {
        !.tail.exists
    }

    conversions || next

    conversions.each_2d {|from,to|
        say ":: Converting: '#{from}' -> '#{to}'"
    }

    var forks = conversions.map_2d {|input, output|
        ffmpeg_convert.fork(input, output)
    }

    forks.each {|t|
        say ":: Waiting..."
        t.wait
    }

    conversions.each_2d {|input, output|

        output.is_file || next

        var output_size = output.size
        if (delete_original && (output_size > 0)) {
            say "Removing: #{input}"
            input.delete || warn "failed to remove: #{$!}"
        }
        elsif (output_size == 0) { # ffmpeg failed
            output.delete    # remove empty file
        }
    }
})