[Theora] problems understanding yuv_buffer format

[David Kment]

hi folks!

once again i am trying to decode a yuv_buffer to a 24 bit RGB buffer.
last time nobody seemed willing to tell me how to do this, so i am 
trying again.
i try to make my questions more simple. what i need to know is:

how many bytes are in each y, u, v array?
what for are these strides?
what exactly is a "plane" in a frame, and what does it do?

what i want to achieve is getting the Y, U and V data for each single 
pixel, so i can convert it to one R, G and B value.

i am trying to apply one of the conversion formulas presented at 
http://www.fourcc.org/fccyvrgb.php, but as of now was never successful 
since the description of the buffer format doesn't help me getting the 
idea....

i would really be very thankful if someone could help me with this :)

regards,

---david