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111 lines
3.5 KiB
Text
111 lines
3.5 KiB
Text
Video Acceleration
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------------------
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Status:
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DRAFT.
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Purpose:
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Provide an standardized generic way to introduce Video Acceleration APIs in
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already available elements instead of duplicating those into specialized ones.
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Provide a mechanism for a light GstBuffer subclassing in order to be able
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exchange VA related context and surfaces between elements.
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Provide some basic primitives to be used in the elements keeping
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the implementation of those in the backends of the helper library.
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The motivation of this proposal is:
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- to avoid multiple duplicty of code
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- to avoid the use of GstBuffer subclassing and be more close to GstBuffer2
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- to avoid the overhead that's introduced with subclassing/GType checks
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- to permit multiple elements interact having a common standard
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Proposal:
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video/x-raw-va
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Light subclassing embedding an structure in the data field of a standard
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GstBuffer.
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struct {
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context;
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surface;
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flags;
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subpicture, x, y, w, h;
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parent *
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...
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} VASurface
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GstVA helper library
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--------------------
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Common API that it's implemented by a backend for each VA API.
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+-------+ +---------------+
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| |----> | VDPAU backend |
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| GstVA | +---------------+
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| | +---------------+
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| |----> | VAAPI backend |
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+-------+ +---------------+
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gst_va_init () : Iterate in the backends and try to initialize those, stops
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when a backend is able to be created.
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bool gst_va_available() : permit to query if there's VA available in runtime.
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GstBuffer * gst_va_buffer_new (vacontext, vasurface, vaflags, parent*,
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free_func*):
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Create a new GstBuffer with the proper light subclass and store on it
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the provided context, surface, flags...
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- parent* and free_func* to implement a mechanism to return surfaces in
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the pool driven by parent.
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gst_va_buffer_get_context (GstBuffer *)
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gst_va_buffer_get_surface (GstBuffer *)
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gst_va_buffer_get_flags (GstBuffer *)
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....
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Some public/private? accessors to be able recover fields from a VA GstBuffer
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internal structure.
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Primitives:
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gst_va_render_display (GstBuffer * va, display, x, y, w, h, ...)
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Put a surface in the screen at the specified position.
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gst_va_render_pixmap (GstBuffer * va, pixmap *, w, h, ...)
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Put a surface in a pixmap, to be used paired with GLX_texture_from_pixmap to
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upload into a OpenGL texture.
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gst_va_render_memory (GstBuffer * va, planes *, strides *, w, h, ...)
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To pull back into main memory a VA surface.
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gst_va_buffer_associate_subpicture (GstBuffer * va, GstBuffer * subpicture,
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x, y, w, h,...)
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Take a reference of subpicture and keep it in va internal structure.
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Use cases:
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Instead of create a new specialized element for each API just change
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a generic element once.
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To add support for a new API just have to create a new backend.
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xvimagesink
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-----------
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- In _setcaps negotiate accept VA kind of stream when gst_va_init and
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gst_va_available tell us that we have hardware capable of it.
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- In _render when the buffers have the VA flag render display it with
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gst_va_render_display()
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videomixer, dvdspu, textoverlay, ...
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------------------------------------
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- In _setcaps negotiate accept VA kind of stream when gst_va_init and
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gst_va_available tell us that we have hardware capable of it.
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- Use gst_va_buffer_associate_subpicture () where necessary.
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