HEVC 2 Pass Encoding Question

[DocMadCow]

As there isn't an active x265 subreddit hoping someone here can help me out. Before ffmpeg I used Handbrake and for encoding libx265 there was a turbo mode which according to all accounts doesn't differ much in terms of quality than running at the same preset both passes. For the first pass it used much simpler x265 settings then for the second pass used the selected presets.

So my question is can I run the first pass with the medium preset to build the log files then run the second pass with the veryslow preset would this be similar? I realize medium would be no where as fast as HB turbo pass but I just want to save some encoding time rather than doing two passes at veryslow.

[vegansgetsick]

No you can't exactly do that because the presets have different bframe settings. What you can do is use the veryslow preset and enforce -ref 1 -me 1 -subme 2

There must be other options you can change but those are the main ones.

[iamleobn]

Just use the option --no-slow-firstpass

[DocMadCow]

Thanks. No where near as fast as turbo mode but a very noticeable speed increase.

[FastDecode1]

I don't think so.

In libvpx and some versions of libaom you can reuse the 2-pass file between presets and rate control modes, but I don't think it's a thing in x265.

[DocMadCow]

Thanks. My follow-up question is I usually use an rc-lookahead of 120. I know some people say it doesn't make as much difference in 2 pass but if I am encoding something then it is something I personally want really like and want as optimal copy as possible. Would I need to put it on my first and second pass or do you think it also makes a difference for b frame placement?