dongmanzui8486
2017-03-30 19:58
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使用cpulimit和PHP减少FFmpeg CPU使用率

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 adding
nice -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 %?

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