RipBot264 Settings Question

[ot_welder]

Hello, and thanks for taking the time to read this post. When using CRF I understand that 16 is the "best" and the higher numbers are "worse" when it comes to picture quality. So basically with CRF you are adjusting the bitrate, right? Higher bitrate=better video.

I've also noticed that the bitrate changes with the profile speed that you choose even when the CRF remains the same. The speed setting is adjusting the amount of compression, right? Ultrafast=least amount and placebo=the most. Since compression decreases video quality aren't these two settings in conflict with each other? Example: CRF=16 and profile speed is placebo. What am I missing here?

[_Al_]

CRF adjusts bitrate at the end , yes,
slower profile uses more reference frames, that will comperes video a bit more but you should get about the same quality as with faster profile, where you get bigger file, think of it, if you let encoder more time, it will "smash" your final size a bit more, but ,

do not go above 3 or 5 reference frames, which means if you set profile slow or slower , encoder will use more than 5 reference frames (HD video) , correct me if I'm wrong ...

[hello_hello]

CRF is designed to give you a specific quality (relative to the source). The harder a video is to compress, the higher the bitrate for any given CRF value. As a result the average bitrate will vary considerably from one encode to the next, but the quality relative to the source should be fairly consistent.
Decreasing the CRF value for a particular video will in turn increase the bitrate as it increases the quality.

The speed presets adjust some of x264's advanced options which effect how efficiently the encoder can compress the video (slower presets use more compression "tricks", which means encoding takes longer) but slower presets also change settings which effect the amount of time the encoder spends working out how to best compress it, so in theory at worst you end up with more efficiently compressed video without any reduction in quality.

In a perfect world I guess the ultra fast preset and the placebo preset would give you exactly the same quality for any given CRF value, except the former would require a much higher bitrate than the latter. I don't think it's that simple though. If anything the faster presets might be inclined to reduce the quality a little as well as compress it less efficiently, but I've not compared them myself. I generally just stick to the default medium speed preset, or if I'm not in a hurry, use the slow or slower preset. Someone else may be able to give you more specific info there.