I'm using FFmpeg with Command Prompt.

I'm setting the process priority with start /low /b.

When pass 1 finishes, it launches FFmpeg again for pass 2 using &&.

start /low /b ffmpeg -i "C:\video.mpg" -c:v libx264 -b:v 1500K -pass 1 "C:\video.mp4" &&
start /low /b ffmpeg -i "C:\video.mpg" -c:v libx264 -b:v 1500K -pass 2 "C:\video.mp4"


Using start /low /b with pass 2 causes the error:

Failed to initialize encoder: Invalid parameter
Additional information: rc_twopass_stats_in.buf not set.

and pass 2 never starts.

  • I think I found the solution, it's start /low /wait /b. – Matt McManis May 27 at 22:53

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