search

rockchip-linux / kernel

BSP kernel source
Other
917 stars 1.07k forks source link

What is difference between rga image scaling and drm image scaling #52

Open nikitos1550 opened 6 years ago

nikitos1550 commented 6 years ago

Hello!

According rk3328 datasheet 2d graphics module (rga driver) and video output driver (accesed by drm) have image scaling capabilities. What is difference? Which one should I use in which case?

wzyy2 commented 6 years ago

RGA scale is memory2memoery. Buffer 800x600 --> Buffer 1920x1080

VOP scale is memory2display Buffer 800x600 --> Screen 1920x1080

nikitos1550 commented 6 years ago

@wzyy2 Thanks. Am I right, that if I want just to scale decoded video than there is no big difference. For example I want to scale 1920x1080 to 1280x720. Same performance with rga and vop. Right?

wzyy2 commented 6 years ago

No...... If you want to store your decoded video, then you have to use RGA sclae. If you want to display decoded video in screen, the you can use VOP scale, but it only could be used through libdrm.

They don't have same performance, since VOP actually didn't scale anything.

To understand what it's VOP scale, you should learn libdrm, drmmodesetplane. To learn what it's RGA sclae, see https://github.com/wzyy2/rga-v4l2-demo.

nikitos1550 commented 6 years ago

Yes, I actually want just to display video not in fullscreen mode, but in some small region. I was thinking about two possabilities, one mpp decoding -> rga (scale) -> vop or mpp decoding -> vop (scale).