Revert "updated audioconvert.h to a newer version" as the new audioconvert fails to compile with libav 0.8.16

This reverts commit 0944a14c8e19ec2c6c38c508e7587b8e72e43d09.
Implement json-to-yaml converter, add support for json in YamlInput, update unittests
update unittest for YamlOutput