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dma-buf.dox readability

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Aleix Pol 2022-06-08 00:06:07 +00:00 • committed by Wim Taymans
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15
doc/dma-buf.dox
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@ -12,18 +12,17 @@ corresponding paragraph.
# Capability Negotiations
The capability negotiation for DMA-BUFs is complicated by the fact, that a
The capability negotiation for DMA-BUFs is complicated by the fact that a
usable and preferred optimal modifier for a given format can only be
determined by the allocator, which has to be invoked with the intersection
of all supported modifiers of all clients. As a result the fixation of the
modifier has to be delegated from PipeWire to the node responsible for
determined by the allocator. This allocator has to be invoked with the intersection
of all supported modifiers for every client. As a result, the fixation of the
modifier is delegated from PipeWire to the node responsible for
allocating the buffers.
## pw_stream_connect
The stream parameters should contain two `SPA_PARAM_EnumFormat` objects for
each format: the first one is used for DMA-BUFs, the second one for shared
memory buffers as a fallback.
each format: one for DMA-BUFs, one for shared memory buffers as a fallback.
Query the list of all supported modifiers from your graphics API of choice.
Add a `SPA_FORMAT_VIDEO_modifier` property to the first stream parameter with
@ -72,13 +71,13 @@ modifier-aware one, or supporting both.
In this case only the modifier `DRM_FORMAT_MOD_INVALID` was announced with
the format.
It is sufficient to check if the `SPA_PARAM_Format` contains the modifier
property as described above. Is that the case use DMA-BUFs for screen-sharing,
property as described above. If that is the case, use DMA-BUFs for screen-sharing,
else fall back to SHM, if possible.
- modifier-aware:
In this case a list with all supported modifiers will be returned in the format.
(using `DRM_FORMAT_MOD_INVALID` as the token for the modifier-less API).
On the `param_changed` event check if the modifier key is present and has the flag
`SPA_POD_PROP_FLAG_DONT_FIXATE` attached to it. In this case extract all modifiers
`SPA_POD_PROP_FLAG_DONT_FIXATE` attached to it. In this case, extract all modifiers
from the list and do a test allocation with your allocator to choose the preferred
modifier. Fixate on that `EnumFormat` by announcing a `SPA_PARAM_EnumFormat` with
only one modifier in the `SPA_CHOICE_Enum` and without the