I run FFmpeg on my server using PHP exec().
It currently uses 100% of the cpu thread while encoding.
I followed this gude that uses a program called cpulimit to reduce it to 30%.
PHP
$args = "nice -19 cpulimit -l 30 -- ffmpeg -y -i intput.avi -vcodec libx264 -acodec aac -b:a 192k -threads 1 output.mp4"
exec(escapeshellcmd($args));
FFmpeg/PHP works, and it will work with nice/cpulimit through the terminal, but after addingnice -19 cpulimit -l 30 -- to the PHP script it no longer works with exec().
Output
FFmpeg output returns blank. I'm not able to see the full output, I tried using:
$output = shell_exec($args);
echo "<p>$output</p>"
and
file_put_contents("/var/www/mysite/logs/$output.log", $line . PHP_EOL, FILE_APPEND);
But they return 1 empty line.
Solution
My thought is that www-data runs FFmpeg and nice/cpulimit may need root?
How can I get PHP exec() to work with FFmpeg args and cpulimit?
Or is there an alternative way to limit the usage %?
I found the answer on this forum post using google translate.
https://murobbs.muropaketti.com/threads/nice-komento-ja-php-n-exec-funktio-ratkaistu.551174/
Define the path to FFmpeg if using nice or cpulimit
nice -19 cpulimit -l 30 /usr/local/bin/ffmpeg -i ...
Now it works through PHP exec().
If safemode is enabled then, the execution of programes are limited. Check this documentation here, http://php.net/manual/en/function.exec.php