When discussing the error associated with relatively high compared to Windows power consumption on AMD APUs with hardware video decoding support, AMD engineer Alex Deucher (lead developer of the amdgpu driver) acknowledged that video display in Linux in principle ineffective.
When outputting video to Linux The following chain is currently used:
- Compressed video stream
- VCN (hardware video decoding module for AMD GPUs)
- Raw YUV data
- Palette conversion, scaling on the GFX module (essentially a 3D accelerator in the GPU, which forces it to increase the core and VRAM frequencies)
- RGB data
- Display output.
How it should work:
- Compressed video stream
- YOU DO NOT
- Raw YUV data
- A display controller that will transform the palette, scale and display.
This could be addressed more efficiently in Wayland compositors, but there's no implementation yet. This issue has been addressed by Microsoft. Windows and Google Android, because there are full-fledged single composers that provide the corresponding capabilities and API - which is not yet available in Linux, because neither X.org nor Wayland can work with YUV streams directly.
Source: opennet.ru
