Convert video files to mp3 audio. Processes some videos simultaneous for better use of multi-core systems. Requires avconv.

vid2mp3.php

#!/usr/bin/env php
<?php
// ##### START config
$files  = glob('*.{mp4,flv}', GLOB_BRACE); // File types to convert to mp3 (video only)
$worker_num = 3; // number of cores +1
// ##### END config
$len = count($files);
$worker_pids = array();

function pr($s) {
	echo '['.getmypid().'] '.$s.PHP_EOL;
}
for($i=0; $i < $worker_num; $i++) {
	$re=pcntl_fork();
	switch($re) {
		case -1:
			pr("Worker wouldn't fork. Kill all");
			foreach($worker_pids as $pid) {
				posix_kill($pid, 9);
			}
			exit(1);
			break;
		case 0:
			pr("Worker $i online");
			$start = $i*ceil($len/$worker_num);
			$end = ($i+1)*ceil($len/$worker_num)-1;
			pr("Allocated $start - $end");
			$child = true;
			break;
		default:
			$worker_pids[] = $re;
			$child = false;
	}
	if($child) break;
}

if($child) {
	pr("Starting conversion");
	for($i = $start; $i =< $end; $i ++) {
		$file = $files[$i];
		if(file_exists($file.'.mp3')) {
			pr("Skipping $i (already exists)");
			continue;
		}
		system('avconv -i "'.$file.'" -vn -y -f mp3 "'.$file.'.mp3" 2>/dev/null');
		pr(($i-$start)."/".($end-$start)." [$i]");
	}
	pr("Done.");
}
else {
	pr("Waiting for workers...");
	foreach($worker_pids as $pid) {
		pcntl_waitpid($pid, $status);
		if(!pcntl_wifexited($status)) {
			pr("Abnormal death of $pid");
		}
	}
}