theora dev - Dec 2006 - yuv strides

Hi all,

 I was looking at the yuv_buffer struct in theora.h today and noticed
this note:

"the strides may be negative in some configurations"

I'm curious when that would be the case or what purpose negative strides
would have?

-Phil

On Wed, Dec 27, 2006 at 05:33:09PM +0000, Philip Heron wrote:
> "the strides may be negative in some configurations"
> 
> I'm curious when that would be the case or what purpose negative
strides
> would have?
The libtheora reference implementation uses this to invert the image. 

Theora's native scanline order is bottom-to-top, but the libtheora api 
uses top-to-bottom. If you don't have postprocessing turned on, the
decoder will return a yuv_buffer with a negative stride to avoid doing
an extra copy to invert the row order.

We mention it in the documation to warn people they need to handle that 
case.

 -r