[excellentswordfight]

Originally Posted by HD MOVIE SOURCE

Thanks for the feedback and the links, Ive been looking for things like this but came up with nothing. I really appreciate it.

If you use a buffsize of 30 Mbps and a bit-rate of 40 Mbps, would that create underflow?

I think you are meaning overflow? But the maxrate is the max-rate, it doesnt mean that you will constantly feed the buffer at that speed (the maxrate for bluray is based on the read-speed of the phyiscal discs, hence the lower value than the h264 spec allows), when both are set the encoder will make sure it doesnt over/underflow on decoders fit for those values. I never really understood why the bluray-spec dictates a lower bufsize, my best guest would that at the time it was set cheap decoders had a rather small buffer.

My current settings are CRF=1 because 0 causes x264 to think its in lossless mode and then disables it, so I just use CRF=1 and the QP values were equal to CRF=0 anyway.

You should not rely on the avg QP-values reported by x264, especially when encoding like you do. When you use such low crf-values with a strict VBV-limit you can end up pretty much with CBR, this will make bit allocation across frames/segment worse, so complex frames wont benefit from high bit allocation that VBR allows for. So even though you get a lower average QP, you can have frames/section were the QP is much higher. This is also what I noticed on your previous SOL encode that I looked at, were complex burst of frames were having a lot of issues that wasnt present when I encoded it at 2pass vbr at a much lower avrage bitrate.

In general, its best to tweak settings in 2pass VBR at the same bitrate for all the runs, then, if you want to use crf, find a value were it ends up at the same average as your test were at. But in the case of bluray, in the real world you will always need to use a target bitrate as there is set size constrain for your video track (for the title to fit on disk with all the other stuff that needs to go in there), and in this case were we are not talking about actually putting titles on disk, and were saving space/bandwith isnt a criteria, just use 2pass VBR at a target that is in the high end of what is actually used by the format (so somewhere in the high 20s as I said previously).

I will test a buffsize of 30'000, hopefully, it won't pull the quality down too much. I've never tried using an open GOP on x265 or x264. It still requires a keyint of 24 though right? If so I don't see how an open GOP would change things though, what does it offer if the keyint must be 24?

Keyint sets the maxiumum distance of I frames, with open GOP those I frames can be non-IDR so you can reference frames across GOP-boundries. When using a short GOP (which 1s is) this can increase compression, I think i've seen papers that shows about 5-10% incease if i remember correctly, although it will greatly depend on the encoding scenario. TBH I have no idea how common open-gop is for actual commercial bluray authoring, but its in-spec to use.