On 06/11/2012 07:41 AM, Brian Paul wrote:
On 06/11/2012 12:59 AM, Pauli Nieminen wrote:
The YCBCR unpack was reading one RGBA value from 4 bytes of YCBCR
texture. But single pixel is only 2 bytes in the format. After
noticing that error Ville told me that second chroma sample has to
be average to match video requirements.
Looking at places where unpack to rgba is called it is possible to get
odd X coordinate and odd number of bytes. That makes unpack operation
complex problem. But I assume that source allocation is 4 byte aligned
always. That should hold for most of allocations but may fail.
Better solution would be threating YCBCR as compressed format
internally. But I suspect that I would break a lot of assumptions
everywhere with that changes.
But same time as I was checking call sites I started suspecting that we
can't ever hit these unpack functions for YCBCR. But I need to study the
code paths a lot more to be sure if that is true.
Changes to fix unpacking:
* Always start reading from the start of chroma pair.
* Always read to the end of chroma pair
* Unpack two RGB values in single iteration
* Read next chroma pair (if available) to calculate average for second
sample.
* Refactor shared color space conversion code to separate function.
Signed-off-by: Pauli Nieminen<pauli.niemi...@linux.intel.com>
This unpack code isn't used during texture sampling by swrast. I think
the only way it would be hit is if one did a glReadPixels from ycbcr
texture attached to a FBO. But we should probably disallow that
(attaching ycbcr textures to FBOs) in the first place.
Either that, or glGetTexImage(GL_RGB) of a GL_YCBCR_MESA texture. I
don't think we're permitted to disallow that.
I think we need a test case for this.
Have you found another path that hits this code?
The changes look OK in any case.
Reviewed-by: Brian Paul <bri...@vmware.com>
-Brian
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