10.01.2022, 23:01
Hello,
I performed some test to see the impact of presets on speed/quality. In Hybrid it is possible to set the encoder so that are provided in output the values of SSIM and PSNR. The explanation of these metrics is outside the scope of this post, in summary they provide a quantitative measure of the encoded quality.
In the table below I reported some summary statistic of the encoding for each available preset in NVEnc (with CQP= 18-20-25).
![[Image: Big-Buck-4-K-Presets.png]](https://i.ibb.co/4SW2cGC/Big-Buck-4-K-Presets.png)
As it is possible to see the presets P1, P2 and P3 are essentially the same since the BitRate, SSIM and PSNR are equal. Starting from the preset P4 (default) the speed, BitRate, SSIM and PSNR start to decrease. But while there is a significant drop in speed between P4 and P7 (quality) there is a little impact on the quality metrics SSIM and PSNR.
The problem regarding these metrics is that it is difficult to say if a given figure is good or bad. For this reason I computed these metrics for 2 specific value of CQP: CQP= 1, which I consider the "placebo" value and represent the best available encoding quality; CQP = 50, which represent the worst possible quality. The calculated values are reported in the table below.
![[Image: Big-Buck-4-K-Quantizer.png]](https://i.ibb.co/Nt8W1Ng/Big-Buck-4-K-Quantizer.png)
As you can see with CQ=1 the BitRate increase to 186,965 kbps, while with CQ=50 drop to 567 kbps. Having defined the best and worst values, I calculated the following weighted figures:
W_SSIM = (SSIM - SSIM_worst) / (SSIM_placebo - SSIM_worst)
W_PSNR = (PSNR - PSNR_worst) / (PSNR_placebo - PSNR_worst)
These values are in a range between 100% (best available quality) and 0% (worst quality). As it is possible to see in this case the P4 (default) preset has a strange behavior, since the quality metrics are a little lower than the performance presets. In summary given the above analysis, in my opinion, the optimal preset to use with NVEnc and RTX 3060 is P3.
I performed some test to see the impact of presets on speed/quality. In Hybrid it is possible to set the encoder so that are provided in output the values of SSIM and PSNR. The explanation of these metrics is outside the scope of this post, in summary they provide a quantitative measure of the encoded quality.
In the table below I reported some summary statistic of the encoding for each available preset in NVEnc (with CQP= 18-20-25).
As it is possible to see the presets P1, P2 and P3 are essentially the same since the BitRate, SSIM and PSNR are equal. Starting from the preset P4 (default) the speed, BitRate, SSIM and PSNR start to decrease. But while there is a significant drop in speed between P4 and P7 (quality) there is a little impact on the quality metrics SSIM and PSNR.
The problem regarding these metrics is that it is difficult to say if a given figure is good or bad. For this reason I computed these metrics for 2 specific value of CQP: CQP= 1, which I consider the "placebo" value and represent the best available encoding quality; CQP = 50, which represent the worst possible quality. The calculated values are reported in the table below.
As you can see with CQ=1 the BitRate increase to 186,965 kbps, while with CQ=50 drop to 567 kbps. Having defined the best and worst values, I calculated the following weighted figures:
W_SSIM = (SSIM - SSIM_worst) / (SSIM_placebo - SSIM_worst)
W_PSNR = (PSNR - PSNR_worst) / (PSNR_placebo - PSNR_worst)
These values are in a range between 100% (best available quality) and 0% (worst quality). As it is possible to see in this case the P4 (default) preset has a strange behavior, since the quality metrics are a little lower than the performance presets. In summary given the above analysis, in my opinion, the optimal preset to use with NVEnc and RTX 3060 is P3.