My bad, I assumed -cpu-used controlled the number of threads.
I retried with "-row-mt 1 -tiles 2x2" (keeping "-cpu-used 8" so the benchmark is comparable to my previous test): the encoding speed is 0.443x of playback speed; top(1) shows about 8 of my 16 cpu threads are utilized.
Without "-row-mt 1 -tiles 2x2" the encoding speed was 0.329x. So these options only increases speed by 34%. This doesn't match the increased in cpu utilization of +60% (5 to 8 threads). Contention on shared data structures? Looks like it's better to just spawn multiple ffmpeg instances working on different source files instead of leveraging the encoder's multi-threading. That way I could get close to 1x of playback speed.
I have 3500 hours of video content. At 1x I need 5 months to reencode all. Heavy. But doable I guess.
I retried with "-row-mt 1 -tiles 2x2" (keeping "-cpu-used 8" so the benchmark is comparable to my previous test): the encoding speed is 0.443x of playback speed; top(1) shows about 8 of my 16 cpu threads are utilized.
Without "-row-mt 1 -tiles 2x2" the encoding speed was 0.329x. So these options only increases speed by 34%. This doesn't match the increased in cpu utilization of +60% (5 to 8 threads). Contention on shared data structures? Looks like it's better to just spawn multiple ffmpeg instances working on different source files instead of leveraging the encoder's multi-threading. That way I could get close to 1x of playback speed.
I have 3500 hours of video content. At 1x I need 5 months to reencode all. Heavy. But doable I guess.