[theora-dev] [theora in hardware] Contents of YUV_BUFFER_ENTRY

Arthur Valadares arthur00 at gmail.com
Mon Jul 24 19:17:53 PDT 2006

Hi everyone, it's my first e-mail to this list (my classmates from college
have sent a few though), so i'ld like first to greet everyone and
congratulate all the people responsible for all the work with this theora

So, to my question:

As you probably know, we are working on an implementation of the theora
codec on hardware. I'm currently responsible for getting the function
ReconRefFrame in dct_decode.c working, and after i understood the code and
finished it in VHDL i found out (after 3 painfull debugging days) that i
don't understand at all what is in LastFrameRecon, ThisFrameRecon and
GoldenFrame (which types are YUV_BUFFER_ENTRY). Generally what i want to
know is: What is inside YUV_BUFFER_ENTRY? More specifically, keep reading...

I know it is a buffer for the pixels, but i just recently found out that
there are more things then just the pixels i need.  This is a complicated
issue, so i'll explain step by step what i understand (which i might be
wrong) and finally to what i dont understand.

1) What i understand: recon_pixel_index_table(i) returns the absolute
location of a relative location. Example: if i do
recon_pixel_Index_table(0), i would get the first pixel of the frame
(although i dont quite get the visual idea of what is the first pixel. Is it
in that black area around the frame? is it the first real pixel? If i do
recon_pixel_index_table(YPlaneFragments) do i get the first pixel in U

2) What i dont understand: i expected to YUV_BUFFER_ENTRY to contain only
the pixels I'ld be using. So in my mind, if i did LastFrameRecon(0) to
LastFrameRecon(YPlaneFragments), for example, i'ld get all the Y pixels. I
realized after careful study of the recon_pixel_index_table that if i wanted
the first pixel of the Y Plane it would not be 0, but in fact,
Now, why is there such an offset? What is in between 0 and ReconYDataOffset?
Is there any more "unexpected" data mixed in the pixels im using? Where am i
going to be needing these pixels? It would help a bunch if i could eliminate
them in hardware, since we're short on memory

Sorry for the terribly long e-mail, but my last attempt at explaining all
this in a hurry resulted in 2 very confused people with communication
problems. So i put it as clear as i could
Thanks a lot for the help

Arthur Valadares
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