[sip-comm-dev] GSoC 09 - Filtergraph

Martin Harvan martinhrvn at gmail.com
Wed Jul 1 14:57:59 CEST 2009

here is my progress report.

So far I have been working on finding path between formats using chain
of codecs. I have decided to do the filter graph builder from scratch
(sometimes getting inspiration from current version) and I have
already completed depth-first search and breadth-first search that are
in most cases able to find correct and (with breadth-first search)
also minimal path (there are cases in which negotiation of format is
needed and that is not handled yet). The speed of the search of course
depends on depth of shortest possible path, but on the whole is good
if up to 4 codecs has to be used, for 5 it is acceptable, but above 5
it just takes too long (I don't think there are any paths that would
require 6 or more codecs currently, I only tested  on cases where path
could not be found due to negotiation of codecs). Speed will also be
addressed after negotiation is implemented, by adding a heuristic
function that will evaluate fitness of given codec considering initial
and final format and current format - creating best-first search that
would first try codecs with highest fitness factor.
I have also created test cases that evaluate the results and runtime
of both algorithms. After best-first search is implemented also tests
for it should be added that would compare how long it took to find
with depth-first vs. best-first. And of course the test should verify
if the same codec chain resulted from the search.
I am starting working on negotiation now and I also would like to do
some cleanup on the code. It shouldn't take too long and I can start
working on the evaluation function for fitness of codec.
Cheers, Martin Harvan
icq: 265 634 317
jabber: martinhrvn at gmail.com
Rita Rudner  - "I was a vegetarian until I started leaning toward the
sunlight." - http://www.brainyquote.com/quotes/authors/r/rita_rudner.html

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