[FFmpeg-user] Why is concat so slow on a powerful machine?

Carl Eugen Hoyos ceffmpeg at gmail.com
Fri Oct 20 01:23:41 EEST 2017

2017-10-19 19:28 GMT+02:00 Christian Johannesen <chrisjohannesen at gmail.com>:

> I tested this using FFmpeg running on a windows server with fiber channel
> attached storage. I am able to duplicate the input file at a rate of
> 460MB/sec. I tested joining two 6 minute 48 second DNxHR SQ 8bit sources at
> 3840x2160 23.98 fps with this command: ffmpeg.exe -f concat -safe 0 -i
> C:\FFMPEG\concat.txt -c:v copy -c:a copy
> C:\Volumes\PTLabSAN\ChrisJ\DNxHR\out.mov. With this process, I achieved 126
> fps. I would suspect the storage as the concat process only used 5% of my
> CPU.

This all makes sense, you could test with -loglevel debug that tells how many
seeks FFmpeg made.

Please remember never to cut FFmpeg's console output, Carl Eugen

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