Quote:
Originally Posted by hello_hello
Yes. I sometimes do it from the opposite perspective. ie starting with the Slow or Slower preset and then selecting slower motion estimation settings etc.
The x264 wiki suggests the point of rapidly diminishing returns is reached at around 5 ref frames.
https://en.wikibooks.org/wiki/MeGUI/x264_Settings#ref
You can check to see how many ref frames x264 actually used when you encoded with --ref 16 (if you still have MeGUI's log files), or you'll find the info under x264's "Standard Error Stream" in MeGUI's Log tab after encoding.
This is from the log of a SD encode using the Slow preset (5 ref frames) and Level 4.1 (L0 being past ref frames and L1 being future ref frames). The way I understand it, for the example below, 96.6% of P frames used 3 ref frames or less.
---[Information] [24/01/18 7:04:12 AM] x264 [info]: ref P L0: 66.8% 12.9% 13.9% 2.7% 3.2% 0.5% 0.0%
---[Information] [24/01/18 7:04:12 AM] x264 [info]: ref B L0: 92.5% 5.7% 1.3% 0.5%
---[Information] [24/01/18 7:04:12 AM] x264 [info]: ref B L1: 98.3% 1.7%
Towards the end of this page there's an explanation as to why x264 shows 7 ref frame percentages for P frames in the example above, even though the Slow speed preset only uses --ref 5.
"The last two are the virtual duplicates produced by the way x264 implements weightp. The decoder of the produced stream won't see them; they don't take DPB (decoded picture buffer) space."
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I don't know all the technical details behind it, all i know is when i left it at it's default setting of very slow and 16 ref frames it takes way longer than when it's less ref frames. Media info of the file says that it's using 16 ref frames and gives a 5.1 profile listing.
What you said about diminishing returns is how i understood it which is why i was thinking i don't need that high ref frames. I've never used that many ref frames before but i haven't used that high of settings either, i was usually always at the 3-6 range. I'm doing specific tasks now where i'm trying to keep the image quality of another picture and so i figure i need really high motion estimation and some of the other higher settings which is why i'm going for "very slow".
I started doing encodes changing it down to using 6 ref frames and it cut the time down by a lot and the results seem okay to me so far.
Alright, i think i finally have a basis to work from now i just needed to be sure i could change the ref frames manually from the preset without it messing something up as my last thing. I'll work from these settings with x264 and then slow preset on x265. Thanks for the help, hello_hello and LigH