Join 3 minutes chunks from dashcam to mkv file.

dashcam.php

#!/usr/bin/php
<?php

define("WORK", '/tmp/'.basename(__FILE__).'.processing');

declare(ticks = 1);

pcntl_signal(SIGTERM, 'signalHandler');// Termination ('kill' was called)
pcntl_signal(SIGHUP, 'signalHandler'); // Terminal log-out
pcntl_signal(SIGINT, 'signalHandler'); // Interrupted (Ctrl-C is pressed)

$pidFileName = basename(__FILE__) . '.pid';
$pidFile = @fopen($pidFileName, 'c');
if (!$pidFile) die("Could not open $pidFileName\n");
if (!@flock($pidFile, LOCK_EX | LOCK_NB)) die("Already running?\n");
ftruncate($pidFile, 0);
fwrite($pidFile, getmypid());

function signalHandler($signal) {
  global $pidFile;
  ftruncate($pidFile, 0);
	if(is_file(WORK)){
		unlink(file_get_contents(WORK));
	}
  exit;
}

$in = "/run/media/sdcard/Video/F";
$out = "/home/data/dashcam";

$suffix = '.MP4';
$split = 180; # sec
$splittolerance = 10; # sec

$chunks = glob("$in/*$suffix");
asort($chunks);

$parts = array();

$part = 0;
$prevtime = 0;

foreach($chunks as $filename){

	$file = basename($filename, $suffix);
	$time = filename2time($file);

	if($prevtime > 0){
		$diff = $time - $prevtime;
		if($diff > ($split-$splittolerance) and $diff < ($split+$splittolerance)){
			if(!is_array($parts[$part]['files'])){
				$parts[$part]['files'] = array();
			}
			array_push($parts[$part]['files'], $filename);
		}else{
			$part++;
			$parts[$part]['files'] = array();
			array_push($parts[$part]['files'], $filename);
		}
		
	}else{
		$parts[$part]['files'] = array();
		array_push($parts[$part]['files'], $filename);
	}
	$prevtime = $time;
}

foreach($parts as $part){
	if(count($part['files']) > 1){
		$from = filename2time(basename($part['files'][0], $suffix));
		$from_hr = date('Y-m-d-Hi', $from);
		$fromday = date('Y-m-d', $from);
		$to = filename2time(basename($part['files'][count($part['files'])-1], $suffix));
		$today = date('Y-m-d', $to);
		if($fromday == $today){
			$to_hr = date('Hi', $to);
		}else{
			$to_hr = date('Y-m-d-Hi', $to);
		}
		$video = "$out/$from_hr-$to_hr.mkv";
		if(!is_file($video)){
			$tmpfname = tempnam("/tmp", __FILE__);
			$fp = fopen($tmpfname, 'w');
			foreach($part['files'] as $file){
				fwrite($fp, "file '$file'\n");
				print "$file\n";
			}
			fclose($fp);

			file_put_contents(WORK, $video);
			print "$video\n";
			system("ffmpeg -loglevel error -safe 0 -f concat -i $tmpfname -vcodec copy -an $video");
			print human_filesize(filesize($video))."\n";
			unlink(WORK);
			unlink($tmpfname);
		}
	}
}

function filename2time($file){
	$year = '20'.substr($file, 4, 2);
	$month = substr($file, 6, 2);
	$day = substr($file, 8, 2);
	$hour = substr($file, 11, 2);
	$min = substr($file, 13, 2);
	$sec = substr($file, 15, 2);
	return strtotime("$year-$month-$day $hour:$min:$sec");
}

function human_filesize($bytes, $decimals = 1) {
  $sz = 'BKMGTP';
  $factor = floor((strlen($bytes) - 1) / 3);
  return sprintf("%.{$decimals}f", $bytes / pow(1024, $factor)) . @$sz[$factor];
}