> Am 11.10.2019 um 07:51 schrieb Anand Veerappan <anandz...@gmail.com>:

> While encoding a video file using FFmpeg we have option to handle thread
> parameter. I used Quad Core Processor and find below my observations.
> *Case 1: Default thread usage*
> By default if we didn't specify thread value FFmpeg internally adjusts
> thread count usage based on the core architecture of the deployment machine.
> Example:
> ffmpeg -i football_1080p.mp4 -c:v libx264 -b:v 3M -bufsize 6M -maxrate
> 4.5M  -g 120 -tune psnr -report football_1080p_3M_threads_1_p.mp4

libx264 defaults to using as many threads as the system provides cores iirc 
(this is not really FFmpeg-related).

> If I repeat this command n times for encoding always the encoded file size
> is similar in all iterations.

But - as you found out - this is not true in general. The fact that 
multi-threaded encoding can lead to different output is not related to FFmpeg 
or libx264 but a property of multi-threaded computing in general (you can of 
course implement the multi-threading with a synchronisation to achieve 
identical results but in the case of video encoding this additional complexity 
that leads to a lower encoding speed is not wanted).

Carl Eugen
ffmpeg-user mailing list

To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".

Reply via email to