I have attempted to encode a large video file with libvpx-vp9 with 2 pass encoding. The first pass took a surprisingly long time, while the second pass was unacceptably slow.
Since libvpx-vp9 can, unlike libx264, receive a benefit to quality from two pass, I would like to ideally make use of the first pass log.
The encoding pages on the trac.ffmpeg.org wiki state that audio can be left out of the first pass, implying that audio related commands don't matter. My own testing suggests that libopus doesn't support 2 pass and is unaffected by a first pass.
What other parameters, if any, can be different between first and second pass? Eg; could I set a different speed (cpu-used) or deadline for the second pass? Are there other video related parameters that can be different? What are the consequences to using drastically different params between first and second pass? Would it cause an error, reduce the benefit from the first pass, nullify the benefit, or result in less quality than 1 pass? Would any answer differ between encoders?
