[FFmpeg-user] Slower Encoding with Threads!

[Mansoor Alghamdi]

Hello ffmpeg team and users,

When using "-thread 16" for encoding videos (x264 and x265) on my dual
Intel Xeon X5670 server running centOS 7, I notice a drop in
performance when compared to single thread encoding! For example, I'm
currently doing an a single-thread x265 encoding for a video and the
speed as reported by ffmpeg is 2.7-2.8x. While if I run the same
command with "-thread 16", I get a speed of 2.5-2.6x only. This looks
illogical to me! Encoding should be faster with multithreading, unless
the my CPUs are not compatible with "-threads" command or threading
cannot be used for encoding.

Any suggestion please?

Thank you.