[XviD-devel] Naive/newbie questions

[skal]

    Hi,

On Tue, 2006-06-06 at 08:58 -0700, Greg Handi wrote:
> 1) In the file interpolate8x8.c why do several methods say "if
> (rounding)" but then do a +1 in the "else" instead? (e.g. below)

 [...]

  Because the mpeg4-v2 format specified two ways of rounding
  ("up" and "down") interpolated samples. It's just the
  syntax.


> 2) also per the interpolation routines, is there a way to get the "src"
> parameter to always be a four byte aligned memory address?  (I realize
> this may not be possible/practicle given how it is derived but I
> thought I should ask)  

   Usually, the "src" reference samples can be anywhere in the picture,
   and in particular are not aligned at all. Now, you can do some
   aligned reads of more samples and shift the whole in the right place
   ("funnel shift"), but ... it's a patented trick:
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6,449,706.PN.&OS=PN/6,449,706&RS=PN/6,449,706

   too bad hey? :)

> If it could be four byte aligned then I could
> make use of some very fast specialized DSP instructions I would like to
> port to that require 4 byte alignment to work.

   i'm interested in looking at the result of your port, in case...

   bye!
Skal