for (int j = 0; j < (*i)->threads (); ++j) {
_threads.push_back (new boost::thread (boost::bind (&Encoder::encoder_thread, this, *i)));
}
for (int j = 0; j < (*i)->threads (); ++j) {
_threads.push_back (new boost::thread (boost::bind (&Encoder::encoder_thread, this, *i)));
}