Bryan Worsley wrote:Can't come up with any chroma up-sampling/sub-sampling combination that replicates the behavior prior to 15.1.1 and I'm not inclined to roll back to 15.1 (again) to see if I can piece it together.
But, of course, I couldn't resist rolling back to 15.1 to try figure this out. I also installed the Premiere Pro Trial to compare alongside Resolve and Vegas 16.
Using the same methodology as described above, I conducted an exhaustive series of tests with the Checker-444 and 422 clips. It would be too much to present all of the results, including the AVISynth chroma resampling 'simulations' and comparative quality metric data. And I'm sure folks are sick of looking at these Checker patterns. So I've compiled an all-in-one summary of the Resolve scope profiles that best illustrate the conclusions I've been able to reach.
The Vegas 16 tests were carried out in 32bit float mode. In the Premiere Pro tests, rendering was set for Maximum Depth.
After opening the link, click on (+) cursor to enlarge. Right click image to copy/save asMy conclusion is that from Resolve 15.1.1 the 444 > 422 re-sampling modality changed to Bilinear, and now behaves in the same way as Premiere Pro. And by that I'm referring to pass-though at the same resolution. All three programs (Resolve, Premiere, Vegas) give the option to choose the interpolation modality that is applied in scaling operations, whether expressed in terms of 'Best', 'Good' etc or by name. Resolve, for example, gives four 'resizer' options - Sharper (default), Bilinear, Bicubic and Smoother, but changing the interpolator does not affect the outcome of these pass-through tests.
What exactly is 'Sharper' by the way ? Prior to 15.1.1 (that is, ending 15.1) the 444 > 422 re-sampling behavior was akin to that in Vegas Pro. The scope profile of the 'pass-through' v210 (Sony 10bit YUV) export of the imported Checker-422 clip is that same as that of the Checker-444 > v210 export. The Resolve 15.1 export of the Checker-444 clip also produces the same profile. In fact, when quality metrics were applied to examine the difference between the two, the SSIM scored lossless for Luma and UV chroma. The PSNR score was a bit lower, but I think it's reasonable to conclude that the re-sampling modality is the same.
The Resolve 15.1 and Vegas v210 exports of the Checker-422 differ because, in Vegas, 422 is passed through 'untouched' when no transforms are applied. As we know (or assume), in Resolve, all imports are up-sampled to 444, so the 15.1 v210 export profile represents the net outcome of up-sampling (likely Bilinear) and sub-sampling - in essence, it is that net outcome that had been the cause for concern and one that was deemed 'sub-optimal'.
Just what that 444 > 422 re-sampling modality was (and is in Vegas) though remains a mystery (to me at least). I could not replicate the outcome with any of the chroma re-sampler combinations tested in the AVIsynth+ 'simulations', including Nearest Neighbor (Point), Bilinear, Bicubic, Lanczos, Spline 16 and 36, Gauss and Sinc. The VirtualDub2 developer thought Bilinear when I passed him the Checker-444 >v210 pattern, but the AVISynth Bilinear upsample/sub-sample simulation matches (perfectly) with the behavior in Resolve 15.1.1/15.1.2 and Premiere Pro.
All I can say is that the same modality must have been applied when the Checkers-422 clip was exported from Natron, so it can't be so obscure. Does anyone know what that is, for sure ? Is it maybe the product of additional spatial filtering ?
Edit: If it's of interest, here's information about the native chroma resample filter implementations in AVISynth(+):
http://avisynth.nl/index.php/Resampling
http://avisynth.nl/index.php/Convert#Chroma_resampleAnyhow, I think I've made some worthwhile progress on this, if only for my own interest. Finding that the 'improved' 4:2:2 sub-sampling' behavior implemented in 15.1.1 is the same as that in Premiere is reassuring.
BTW - I have also been doing some tests with 'real world' material and the metric analyses appear to back this up. I'm now in the process of scrutinizing the images.
BMD (Rohit), I've put alot of work and thought into this. Give me a sign if I'm right about 15.1.1 at least -
for yes,
for no, you're way off.