Hello all,
It's been about a week and a half since my last update, and there is much progress to share.
In my last update to this thread, I noted that we had identified two underlying causes of the "block artifacts" that have been reported, especially in bright areas of HDR content. We wanted to have a little bit more certainty around those before sharing details, but now is the time.
As I think everyone reading this thread knows, Strato V, M, and E are based around a new chipset compared to the older-generation Strato players like Strato C, S, and the original Strato. This new chip has lots of great features, like the ability to play Dolby Vision content, decode multichannel audio, and so on. It also includes a video scaling engine with lots of capabilities including image enhancement functions that are used when up-scaling content (e.g. HD played out as 4K).
Useful as those image processing features are when upscaling, you don't want them on when playing content at its native size, because they can introduce artifacts. So of course we turn them off whenever we're not scaling.
Well, it turns out that the chip had a sneaky trick up its sleeve. Readers of this thread will also know that as part of playback of letterboxed content, we blank out the part of the image that is the black letterbox bars. This is so that they appear truly black during playback, which looks better and also facilitates the function of things like auto-aspect detection in video processors. It turns out that for the chip's internal purposes, "blank out these portions of the image" is a feature of the scaler. Which means that although we have image processing turned off when the scaler is inactive, the scaler is in fact active much more often than we expected.
So, this is good news. We have made image comparisons now between the currently shipping software and an engineering build with all of the image-processing functionality disabled, and many of the "block artifacts" disappear. The image processing features also include some noise reduction that can cause a loss of grain detail, so turning those features off also restores that detail. That means that even without updating encoding, the playback of existing files will look better once we have deployed a fix to the player software to disable the unintended processing.
But, we're also making updates to our encoding. Without wading too far into the weeds on this, we have identified some improvements that can be made to our encoding "recipe" that make meaningful differences in preserving grain structure and minimizing blocky artifacts in the chroma channels of the encoded image. When combined with disablement of the inadvertent image processing, the resulting playback is significantly improved. Even on older Strato hardware that is not affected by the image processing bug, the updated encodes will deliver better quality.
Finally, an update on tools. I mentioned previously that we were working on improvements to our workflow and tools. In addition to improving our processes to better catch things like bogus HDR metadata supplied with the master files, we've also been working to improve our automated analysis of encoded movies. We already had automated tools that were run on every movie to ensure that the encoded files are preserving image detail. To that existing tool, we are now deploying a color analysis tool that will ensure that the encoded file's colors are faithful to the original. Color shifts like those that have been identified in this thread would immediately be flagged by this automation, so that corrective action can be taken. With our combined adjustments to both process and recipe, all known sources of color shift have been addressed, but this tool will provide a backstop to help ensure that we catch some future source of error. (Note: we are still looking at reported difference in red saturation on a few recent titles.)
Now, having said all of this, the obvious question is: when will we start seeing these improvements?
On the encoding front, we have already begun using an updated recipe on some recent releases with good results, so we will continue to use it on suitable content even as we continue to refine it. We will also continue making updates to titles that were affected by color shift or metadata issues, and those will naturally be processed with the latest recipes as well.
On the player side we are working on a software update that will disable the undesirable image processing. This turns out to be a bit of an invasive change, because we do need some of this functionality to be engaged when we're actually scaling content, which includes both upscaling (HD -> 4K) and certain CinemaScape modes. This makes a quick-fix change too risky to include in the next kOS software update, which is already nearing completion and getting ready for final testing. However, this work is being performed with a high priority, and we will release it in a subsequent update as soon as it has been adequately tested. We'll be able to share more about that release timeframe once the work is done and in testing.
I hope that this update will reassure you all that we are taking any and all quality issues very seriously, and the work to resolve them is being done at the highest priority.
Let me close by just making a note here that I will be on vacation for the next week, so please don't be alarmed if I'm not especially responsive here on the forums. I'll try to look in when I can, and I know John will also be watching (although please note that next Monday is also a holiday for him in Canada).
Thanks for reading this far. I'll share more updates as I have them.
