Optimization idea: soft XvPutImage

Maarten Maathuis madman2003 at gmail.com
Sun Sep 21 04:07:11 PDT 2008

On Sun, Sep 21, 2008 at 11:10 AM, Adam Richter
<adam_richter2004 at yahoo.com> wrote:
> On Fri, 9/19/08, Soeren Sandmann <sandmann at daimi.au.dk> wrote:
>> Adam Richter <adam_richter2004 at yahoo.com> writes:
>> >     I want to suggest a way we could eliminate a
>> substantial
>> > amount of data copying [...]
> [...]
>> Pixman, the software implementation of XRender already has
>> support for
>> YUV formats, so all that is really required is to just
>> export YUV
>> picture formats through the XRender protocol. [...]
> Thank you for pointing out that pixman has some limited YUV reading support already.  The biggest problem that I see with using the X Render is that it lacks stretch and shrink, at least if I understand correctly from looking at the protocol specification here:
> http://gitweb.freedesktop.org/?p=xorg/proto/renderproto.git;a=blob_plain;f=renderproto.txt
> See lines 758-766:
> Composite
>        op:             PICTOP
>        src:            PICTURE
>        mask:           PICTURE or None
>        dst:            PICTURE
>        src-x, src-y:   INT16
>        mask-x, mask-y: INT16
>        dst-x, dst-y:   INT16
>        width, height:  CARD16
> The last two parameters (width and height) presumably apply to both source and destination rather than having separate parameters for the source and destination rectangles.
> This also appears to be the case when I look in the header for the pixman library  (pixman-0.12/pixman/pixman.h) at the declaration of pixman_blt.  It also only has a width and height, which presumably apply to both source and destination.
> Even if you do not want to do stretch, I believe that the X Render extension would require first copying the YUV data to a drawable and then doing a drawable->drawable block transfer operation to do the YUV transformation.  In comparison, XvPutImage is a single call takes an XImage, which can be in shared memory, and would normally be in YUV, and specifies the YUV->RGB conversion and stretch in a single operation.
> Thanks for your input, especially the tip about some YUV support already existing in libpixman.
> Adam Richter
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Src and Mask pictures have a transform, which can translate and rotate
coordinates as you please.

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