[FFmpeg-devel] [PATCH v3 14/18] swscale/graph: add new high-level scaler dispatch mechanism

[Anton Khirnov]

Quoting Niklas Haas (2024-10-24 12:02:41)
> On Thu, 24 Oct 2024 11:30:12 +0200 Anton Khirnov <anton at khirnov.net> wrote:
> > Does this (or can it) support copy-free passthrough of individual
> > planes, for cases like YUV420P<->NV12?
> 
> Not currently, no. We could switch to AVBufferRefs for the plane pointers to
> add this functionality down the line, but it's not a high priority because
> doing this will require the much harder problem of rewriting the underlying
> scaler dispatch logic to begin with.
> 
> Doing this would not be terribly difficult either way, but the problem is that
> swscale currently does not exactly have a good concept of what's happening
> to each plane - it's all a jumble of ad-hoc cases.
> 
> One of my plans for SwsGraph is to first make a list of operations to perform
> on each plane, and then eliminate reduntant passes to figure out what special
> cases and/or noop passes can be optimized. But this has to wait a bit, as I'm
> first working on the immediate goal of adding support for more complex
> colorspaces (by chaining together multiple scaling passes).

Right, as long as it's reasonably implementable down the line I have no
objections. My concern was mainly about locking ourselves into a
high-level API that does not allow this, and this constraint then
propagating into the lower-level implementations.

-- 
Anton Khirnov