Hírolvasó

ort does just that: it’s a full-blown rewrite of the merge strategy that aims to emulate the same concepts behind recursive while avoiding many of its long-standing performance and correctness problems. In a merge containing many renames, ort outperforms recursive by 500x. For a series of similar merges (like in a rebase operation), the speedup is over 9000x, in part due to ort's ability to cache and reuse results from previous merges.

Anyway, it's not a huge release, although it's also not a remarkably small one like 5.15 was (ok, "remarkably small" is relative, when even such small releases have 10k+ commits).. There's a bit of everything in here, and you can look to the appended mergelog for some kind of flavor, but I guess the folio work is worth mentioning, since it's an unusually core thing that we don't tend to see most releases.

Previously I mentioned having AMD VCN h264 support. Today I added initial support for the older UVD engine[1]. This is found on chips from Vega back to SI.

I've only tested it on my Vega so far.

I also worked out the "correct" answer to the how to I send the reset command correctly, however the nvidia player I'm using as a demo doesn't do things that way yet, so I've forked it for now[2].

The answer is to use vkCmdControlVideoCodingKHR to send a reset the first type a session is used. However I can't see how the app is meant to know this is necessary, but I've asked the appropriate people.

The initial anv branch I mentioned last week is now here[3].

[1] https://gitlab.freedesktop.org/airlied/mesa/-/commits/radv-vulkan-video-uvd-h264

[2] https://github.com/airlied/vk_video_samples/tree/radv-fixes

[3] https://gitlab.freedesktop.org/airlied/mesa/-/tree/anv-vulkan-video-prelim-decode

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Last week I mentioned I had the basics of h264 decode using the proposed vulkan video on radv. This week I attempted to do the same thing with Intel's Mesa vulkan driver "anv".

Now I'd previously unsuccessfully tried to get vaapi on crocus working but got sidetracked back into other projects. The Intel h264 decoder hasn't changed a lot between ivb/hsw/gen8/gen9 era. I ported what I had from crocus to anv and started trying to get something to decode on my WhiskeyLake.

I wrote the code pretty early on, figured out all the things I had to send the hardware.

The first anv side bridge to cross was Vulkan is doing H264 Picture level decode API, so it means you get handed the encoded slice data. However to program the Intel hw you need to decode the slice header. I wrote a slice header decoder in some common code. The other thing you need to give the intel hw is a number of bits of slice header, which in some encoding schemes is rounded to bytes and in some isn't. Slice headers also have a 3-byte header on them, which Intel hardware wants you to discard or skip before handing it to it.

Once I'd fixed up that sort of thing in anv + crocus, I started getting grey I-frames decoded with later B/P frames using the grey frames as references so you'd see this kinda wierd motion.

That was I think 3 days ago. I've have stared at this intently for those 3 days blaming everything from bitstream encoding to rechecking all my packets (not enough times though). I had someone else verify they could see grey frames.

Today after a long discussion about possibilities, I was randomly comparing a frame from the intel-vaapi-driver and from crocus, and I spotted a packet header, the docs say is 34 dwords long, but intel-vaapi was only encoding 16 dwords, I switched crocus to explicitly state a 16-dword length and I started seeing my I-frames.

Now the B/P frames still have issues. I don't think I'm getting the ref frames logic right yet, but it felt like a decent win after 3 days of staring at it.

The crocus code is [1]. The anv code isn't cleaned up enough to post a pointer to yet, enterprising people might find it. Next week I'll clean it all up, and then start to ponder upstream paths and shared code for radv + anv. Then h265 maybe.

[1]https://gitlab.freedesktop.org/airlied/mesa/-/tree/crocus-media-wip

Generics will be one of our focuses for 2022. The initial release in Go 1.18 is only the beginning. We need to spend time using generics and learning what works and what doesn’t, so that we can write best practices and decide what should be added to the standard library and other libraries. We expect that Go 1.19 (expected in August 2022) and later releases will further refine the design and implementation of generics as well as integrating them further into the overall Go experience.