[mythtv] MacOS X MMX yuv420_2vuy Patch

Andrew Kimpton awk at awkward.org
Wed Sep 13 18:45:25 UTC 2006

Quoting Todd Ignasiak <ignasiak at gmail.com>:

> The 0.20 final seems to be working very well for me.  I haven't used
> it a lot yet, but thus far it's been stable and performance is
> improved over previous versions.
> I noticed two minor issues, can anyone else confirm them on their Mac?
> 1) When I turn off the vector acceleration option, I no longer get a
> crash.  I now get a distorted picture, where the colors are primarily
> purple and green, and the distorted image is tiled on the screen
> several times.
What you're seeing is the original YUV420 planar data. The Y/Luma  
plane will look a lot like a black/white version of the video. The  
UV/Chroma planes will tend to be between purple and green.

Since the data is laid out in memory as seperate planes (Y then U then  
V) you'll see them as tiles on the output window if they're not being  
convered prior to display.

If you turn off the 'accelerate' option then the code doesn't use the  
MMX conversion routines, and on Intel machines also doesn't attempt to  
setup QuickTime to do the conversion (since that crashes Intel  
machines). Hence the od images.

> 2) AC3 to SPDIF passthrough results in messed up sound.   After
> glancing through the code, I don't think SPDIF passthrough is in the
> Mac mythtv code.  Has anyone else tried AC3 audio?

There's some commentary about this on the Wiki - they sense there is  
that some required byteswapping is missing. I don't have a AC3/SPDIF  
decoder attached to my Mac so I can't give any further insight.

Andrew 8-)

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