sigstop and x264

Because FPS is defined as follows: FPS = frames_encoded / time_elapsed If you suspend the x264 process, it will stop encoding frames for obvious reasons. But this won't stop the universe. Time will move on ;) So if you resume the x264 process later, a lot of time has elapsed in which not one single frame was encoded. Consequently the FPS value will drop! The only easy way to "fix" this would be calculating FPS over an interval (e.g. the last minute) instead over the whole encoding process. But that would change the meaning of FPS! At the moment FPS is the average FPS throughout the whole encoding process.

So even with a sigstop, the process can get the CPU power to calculate fps?

the underlying principle of why the fps drops on resuming is the following: x264 takes the clock time of when the processing started, and then takes the current clock time to generate a difference and then uses it in combination with the number of encoded frames to give you an average fps rate. the starting clock time won't change, so the difference from the starting lock time to the current continues to increase as time flows, whether x264 is allowed to process or not.

There's a patch written a while back (by Loren?) that should fix this: It probably needs some updating though.