How to Run FFmpeg with Lower Process Priority

Running resource-intensive video encoding tasks with FFmpeg can easily consume your entire CPU, causing your operating system to lag. This article provides a quick and direct guide on how to configure and run the FFmpeg command with lower process priority on Windows, Linux, and macOS, ensuring your system remains responsive for other tasks while your media processes in the background.

Linux and macOS (Using nice)

On Unix-like operating systems, you can use the built-in nice utility to launch FFmpeg with a lower CPU scheduling priority. Niceness values range from -20 (highest priority) to 19 (lowest priority/most “nice” to other processes).

To run FFmpeg at the lowest priority, prepend your command with nice -n 19:

nice -n 19 ffmpeg -i input.mp4 output.mp4

If the FFmpeg process is already running, you can lower its priority dynamically using the renice command combined with the process ID (PID):

renice +19 -p <PID>

Windows Command Prompt (Using start)

In the Windows Command Prompt (cmd.exe), you can use the start command to initiate a process with a specific priority class. The available options for lowering priority are /belownormal and /low.

To run FFmpeg at the lowest priority level:

start /low /b ffmpeg -i input.mp4 output.mp4

Note: The /b switch is highly recommended because it forces the application to run in the current Command Prompt window instead of opening a new one.

Windows PowerShell (Using Start-Process)

If you are using PowerShell, you can lower the process priority using the Start-Process cmdlet with the -PriorityClass parameter. The target values for lower priority are BelowNormal or Idle.

To run FFmpeg with the lowest (Idle) priority:

Start-Process ffmpeg -ArgumentList "-i input.mp4 output.mp4" -PriorityClass Idle -NoNewWindow -Wait

Note: The -NoNewWindow switch keeps the output in your current shell, and -Wait ensures PowerShell waits for the encoding to finish before accepting new commands.