Benefit of opt-qp-pps, opt-ref-list-length-pps and opt-cu-delta-qp

[ShortKatz]

I was wondering how beneficial the options --opt-qp-pps, --opt-ref-list-length-pps and --opt-cu-delta-qp are. The documentation states, they optimizes different things. Optimization always sounds to me like a good thing. But this options are disabled by default. So, how beneficial are this options and are there any downsides when using it?
It seems they don't change anything on encoding speed and file size in my quick test.

By the way, I've read, that --idr-recovery-sei could be helpful if you want to stream your video file from a NAS. Is that correct?

[rwill]

I was wondering how beneficial the options --opt-qp-pps, --opt-ref-list-length-pps and --opt-cu-delta-qp are. The documentation states, they optimizes different things. Optimization always sounds to me like a good thing. But this options are disabled by default. So, how beneficial are this options and are there any downsides when using it?
It seems they don't change anything on encoding speed and file size in my quick test.

By the way, I've read, that --idr-recovery-sei could be helpful if you want to stream your video file from a NAS. Is that correct?

--opt-qp-pps, --opt-ref-list-length-pps
Savings: 0 to couple bits per GOP. Most likely useless.

--opt-cu-delta-qp
Oof, I would not use that one as it might hurt quality. Savings: 0 to couple bits per CU

--idr-recovery-sei
Needs Player support which is most likely not present. So no, I think this does not help at all. Costs a couple of bytes per GOP.

[benwaggoner]

--opt-cu-delta-qp
Oof, I would not use that one as it might hurt quality. Savings: 0 to couple bits per CU

I have seen --opt-cu-delta-qp reduce QP variation in a frame somewhat, which improved quality in really grain high resolution stuff that by default had really severe QP variation that clearly revealed the CU structure.

Other techniques can help with that sort of scenario, so I've not experimented that deeply with it. I should.

[ShortKatz]

Thanks for your answers. :-)