git blame says:
    109 Stefano Sabatini
      7 Clément Bœsch
      2 Reimar Döffinger
      2 Michael Niedermayer
      1 Reinhard Tartler
      1 Mans Rullgard

Initial commit:
commit 1ee410f3
Author: Stefano Sabatini <stefano.sabatini-lala@poste.it>
Date:   Sat Sep 25 01:56:58 2010 +0000

    Add asrc_anullsrc - null audio source.

    Based on a patch by "S.N. Hemanth Meenakshisundaram" smeenaks!ucsd!edu.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>