[vlc-devel] [PATCH 00/19] picture cleaning

[Steve Lhomme]

On 2020-07-30 18:10, Rémi Denis-Courmont wrote:
> Le torstaina 30. heinäkuuta 2020, 15.54.29 EEST Alexandre Janniaux a écrit :
>> Hi,
>>
>> I'm not at ease with this patchset, it feels like removing the
>> picture_resource_t layer and doing it by hand.
> 
> Leaving aside my minor detail comments, I think the patchset makes sense.
> 
> The whole point of push-buffers was to uniformise picture buffer allocation.
> Everything should be allocated as shared memory that can be manipulated
> locally, passed onto compositor with zero copy IPC, and eventually exchanged
> with sandboxed decoders orf ilters. picture_NewFromFormat() takes care of
> that. Pictures resources should not be needed anymore.
> 
> Regardless we still need a mean to wrap opaque picture buffers, which cannot
> really use picture_NewFromFormat().
> 
> However...
> 
>> This value previously held vout data in the pull model, if
>> I am not wrong. I still use it in scenario where the vout
>> binds an object (eg. wl_buffer) to an underlying object in
>> the picture (eg. a GBM buffer).
> 
> If we need to handle non-opaque pictures coming from an input peripheral (as
> opposed to going to an output peripheral), then we need something like similar
> to picture_NewFromResource(). I guess that is your implication?

It seems VideoToolbox does that. See cvpxpic_create_mapped(). D3D11 and 
D3D9 have something similar as well. It's always to copy to/from CPU 
from/to GPU. Just using planes could work. (VT even does the plane 
copying manually)

vmem, kms and fb display modules could also use an approach with just 
planes.

That involves more patching and more testing. But now they are more 
visible. It's all the picture_NewFromResource() calls with a NULL gc.

See branch https://code.videolan.org/robUx4/vlc/-/commits/picture-clean/2

> Even if that use case materialises, picture_NewFromResource() cannot handle it
> as it stands: it lacks provision for passing the file descriptor, mapping offset
> and size. So that would need a whole new picture_New*() function in any case.
> 
> -- 
> 雷米‧德尼-库尔蒙
> http://www.remlab.net/
> 
> 
> 
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