[mythtv] MacOS X MMX yuv420_2vuy Patch

[MythTV]

On Sep 6, 2006, at 2:54 PM, Nigel Pearson wrote:

>> I'm no longer seeing a crash but I'm seeing a problem on startup or a
>> channel change with HDTV.
>>
>> The live TV freezes and I get a constant "NVP: Timed out waiting for
>> free video buffers."
>
> 	Todd and Paul are. Paul's tests seem to indicate
> some strange problem in the MMX function itself? See:
> http://svn.mythtv.org/trac/ticket/2312
>
>
> 	Mino, you mentioned some sort of harness that you used
> to test the MMX code. If it is standalone, could you please
> send me a copy?
>
> 	Otherwise, is there any chance of getting you to check
> for buffer overruns in the function? Having some dummy data
> (say a few hundred bytes of 0xF00F0FF0) either side of both
> the source and destination buffers should be enough to show
> any errant writes.
>
>
> 	And if any of you could provide -v playback output that
> shows the problem, it may help us.
>
> --
> Nigel Pearson, nigel at ind.tansu.com.au|  "Let's see how Spike is going"
> Telstra Net. Eng., Sydney, Australia |              ...
> Office: 9202 3900    Fax:  9261 3912 |"I'd like to keep Spike as my
> pet."
> Mobile: 0408 664435  Home: 9792 6998 |        Illyria - Angel
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>

Nigel,

Here's a quick patch that will revert to the non-vectorized code for  
the conditions that will create a buffer overrun. This is similar to  
what the Altivec code does.

Looking at the log posted in Trac the video size is 720x576 which the  
MMX routine should be able to handle.  The only other thing I can  
think of in the MMX code would be if the buffers aren't aligned but I  
believe that would create a Machine Check exception.

I'm not at my Myth machine so I haven't had a chance to try this  
patch.  If it doesn't work, let me know.

Mino



Index: yuv2rgb.cpp
===================================================================
--- yuv2rgb.cpp (revision 11068)
+++ yuv2rgb.cpp (working copy)
@@ -711,6 +711,7 @@

      int x,y;

+    if (!((h_size % 16) | (v_size % 2))) {
      for(y = v_size/2; y--; )
      {
          ibuf1 = ibuf2;
@@ -779,6 +780,13 @@
          ubuf += uv_stride;
          vbuf += uv_stride;
      }
+    }
+    else
+    {
+        // Fall back to C version
+        non_vec_2vuy_yuv420(image, py, pu, pv, h_size, v_size,
+                            vuy_stride, y_stride, uv_stride);
+    }
}
#endif // MMX

Mino