How do I enable FFMPEG logging and where can I find the FFMPEG log file?

Question

I want to be able to log FFMPEG processes because I am trying to work out how long a minute of video takes to convert to help with capacity planning of my video encoding server. How do I enable logging and where is the log file saved. I have FFMPEG installed on a CentOS LAMP machine.

Answer 1

FFmpeg does not write to a specific log file, but rather sends its output to standard error. To capture that, you need to either

• capture and parse it as it is generated
• redirect standard error to a file and read that afterward the process is finished

Example for std error redirection:

ffmpeg -i myinput.avi {a-bunch-of-important-params} out.flv 2> /path/to/out.txt 

Once the process is done, you can inspect out.txt.

It's a bit trickier to do the first option, but it is possible. (I've done it myself. So have others. Have a look around SO and the net for details.)