Hello,
I have tested a lot of tv box to decode video, and lot use special kernel of vendor ( the kernel provide by android 3.14 ... ) with not completely opensource solution.
And a guy (maxime jourdan) have make an "hack" of the amlogic, and use V4L2M_M2M to make the amlogic hardware decode with new kernel ( patch in 4.19 if i remenber ).
It's not perfect ( the performance is poor than the special kernel ) but it's works and it's not a vendor solution and completely opensource .
And the guy explain it :
In english i can understand
It's a french guy
It's my new hero ...