Great filter!
From what I know, the main problem is the lack of a proper filter/scaler infraestructure.
There's the following related OpenTasks:
-
Extend plugin system
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Improve the default backend (specially if wanting GPU acceleration)
The main problem is the need of a programmer able to do the task, not the filter/scaler itself. There has been tons of not only requests, but patches of new filters/scalers for ScummVM. But those were quite hackish and problematic to maintain too, so they were declined.
They have nothing against new filters, but the infraestructure must be improved first. And most developers in the Team have more interesting things to do, like RE and improving the current available engines.
Anyway, that's something that can be better explained by a member of the ScummVM Team.