Get indistinguishable quality encodes using nvenc?

[nixiejames]

Is it possible for nvenc to achieve an output similar to x264 crf 15, or is it impossible because of how it prioritizes speed over quality?

[KarMa]

Using a high enough bitrate, yes.

[nixiejames]

Would you recommend a cbr/vbr pass over a rate control mode setting like cqp for nvenc? If so, at what bitrate is usually recommended for, let’s say, blurays?

[KarMa]

If you want a quality like x264 CRF 15, then you need to use a quality mode in NVENC too. You can't really do 1:1 equivalent as CRF in x264 is unique but you can try experimenting with CQP 15 in NVENC, and drop the number further until you think they are the same.

[nixiejames]

All I really want to know if it’s possible to achieve something that is visually the same as x264’s because a lot of people keep telling me that nvenc sacrifices quality and generates bigger files when I don’t have a problem with the size. You actually read my mind when you told me to try cqp15 as that was actually a setting I used before when screen recording with OBS.

[KarMa]

All I really want to know if it’s possible to achieve something that is visually the same as x264’s because a lot of people keep telling me that nvenc sacrifices quality and generates bigger files when I don’t have a problem with the size. You actually read my mind when you told me to try cqp15 as that was actually a setting I used before when screen recording with OBS.

NVENC is a hardware based encoder while x264 is a CPU based encoder. It can certainly achieve similar quality to x264, I think it even offers a lossless mode (big file sizes). NVENC just isn't going to be as efficient at any given bitrate.

[Allan74]

You may want to look into some VMAF testing that was done recently by an Aussie Gaming Blog (I'll try and find the link).

They summarize through extensive testing that Turing's implementation of NVENC HEVC using either the 'Slow' or 'HQ' settings is Superior in terms of not only speed, BUT QUALITY ALSO, when compared to CPU/Software encoded h265 at bitrates of 8k @ 1440p....meaning that 1080p should be a piece of cake at similar.

It also had shown that Pascal 'HQ' HEVC was a near match to h265 Slow at 8k, with even Maxwell 'HQ' HEVC coming in somewhere in the h265 Medium range of perceptual quality, again, @ 1440p 8k.

Would it be fair to say that in terms of perceptual quality, 1440p 8k would be somewhere in the 6-7k range for 1080p ?

[KarMa]

You may want to look into some VMAF testing that was done recently by an Aussie Gaming Blog (I'll try and find the link).

Yeah I remember him, the guy who refused to share his videos but to simply trust him.

[Sharc]

If you want a quality like x264 CRF 15, then you need to use a quality mode in NVENC too. You can't really do 1:1 equivalent as CRF in x264 is unique but you can try experimenting with CQP 15 in NVENC, and drop the number further until you think they are the same.

As I understand it, CQP in NVEnc means constant quantizer rather than constant quality.
The CRF xx.xx equivalent mode is
a) for ffmpeg's NVEnc: -rc vbr_hq -cq xx.xx -b:v 0k
b) for rigaya's NVEncC: --vbrhq 0 --vbr-quality xx.xx