Sebastian Krzyszkowiak @dos@librem.one

@pavel After eliminating glReadPixels and having the output buffer mmaped instead: "18.9 MB in 0.08s = 244.4 MB/s"

After putting glTexImage2D out of the loop to emulate zero-copy import from V4L as well:
"18.9 MB in 0.05s = 400.1 MB/s"

https://dosowisko.net/stuff/bwtest.patch

@brie Unless there's a ton of dependencies to take care of as well, in my experience simply building a fresher deb by myself is usually the best option.

@pavel Megapixels is not an example of how to do things in the most performant way :) OpenGL operates in a VRAM-centric model, it's very copy-heavy. We don't need to copy things around, as our GPUs operate on the exact same memory CPUs do.

See GL_OES_EGL_image_external and https://docs.kernel.org/userspace-api/media/v4l/dmabuf.html

@pavel On 9f076a5, I'm getting 88MB/s with one green channel, 82MB/s with two and 105MB/s with nothing but static gl_FragColor. The three copies it does could be eliminated and I believe texelFetch could make it slightly faster on the GPU side too.

@pavel I'm confused. V4L lets you stream to a CMA dmabuf which should be importable as GL_TEXTURE_EXTERNAL_OES, right? Or am I missing something?

@mgorny No właśnie czekam aż policzy.

@tizilogic @pavel It's either 8-bit int, or 10-bit int stored as 16-bit.

GC7000L supports compute shaders, but etnaviv isn't there yet.

Naive debayering is easy, but for good picture quality you need much more than that.

@pavel Since I assume you're going to want to pass the rendered image into some kind of video encoder, you may want to make sure that you match stride and alignment requirements with your target buffer so etnaviv will be able to perform linear rendering rather than de-tile it afterwards (though IIRC it's currently gated behind ETNA_MESA_DEBUG).

@pavel No, it's

RGRGRG
GBGBGB

You lose meaningful data if you ignore half of green pixels.

I see no reason why it couldn't be done. Just take care not to introduce needless copies in your processing path. dmabufs are your friends.

@edavies These were Polish eliminations. This year it goes worldwide btw 😁

pit stop #shotonlibrem5

@miketango judging from its face I guess no 🤷

>tfw not enough trams #shotonlibrem5

old tram / new tram #shotonlibrem5

@devrtz My hometown has won the competition and advanced to the world cup 🥳

Tram bowling 😎 #trams #shotonlibrem5