[Mesa-dev] About merging pipe-video to master

Christian König deathsimple at vodafone.de
Mon Jul 11 09:24:52 PDT 2011

Hi guys,

as the subject already indicates: I'm about to merge pipe-video to
master and just wanted to ask if anybody has still any objections?

After following Jose and Younes discussion on mesa-dev about how to
design such an abstraction layer I took another round of cleaning up the
interface and moved some more parts into the state tracker.

So the interface between the state tracker and drivers only consist of
the following now:

1. two additional functions for the screen object: get_video_param and
is_video_format_supported. get_video_param gets a parameter for a
specified codec (like max width/height of decoding target, which could
be smaller than texture max width/height), and is_video_format_supported
which checks if a texture format is supported as a decoding target for a

2. create_video_decoder function in the pipe_context object, which
creates a decoder object for a given codec. The decoder object in turn
includes everything needed to decode a video stream of that codec and
uses pipe_video_decode_buffer objects to hold the input data of a single
frame of that video codec.

3. create_video_buffer function in the pipe_context object, which
creates a video_buffer object to store a decoded video frame. This
video_buffer object is then used for both rendering to the screen with
normal pipe_context functionality and also as the input for reference
frames back to the decoder.

The pipe_video_buffer object is there because I think hardware decoders
need some special memory layout of the different planes of a yuv buffer.
There is a standard implementation that just uses normal textures as the
different planes for yuv buffer, which can be used by a driver when
there is no need for a special memory layout or when the driver just
uses shader based decoding.

The other option would be adding a PIPE_BIND_VIDEO_BUFFER flag to the
resource creation functions, but I don't want to repeat functionality in
the different drivers and as far as I can see the current resource
functions (samplers/surfaces) can't be used to create a surface for just
one plane/component of a yuv buffer and we could still clean that up to
use the standard resource functions if the need arise.

Everything else, especially the vl_compositor functionality, is now part
of the state tracker instead of the driver. The interface was mostly
designed keeping two things in mind: First it should abstract the
functionality of hardware video decoding from the state tracker and
second it should be possible to implement a wide variety of different
video decoding apis with it. For the second part I checked that it's at
least possible to do XvMC,VDPAU,VAAPI and DXVA with it.

So what do you guys think about it?


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