Change the flushing state of all the pads in the collection.
No pad is able to accept anymore data when flushing is true. Calling this function with
flushing false makes this accept data again. Caller must
ensure that downstream streaming (thread) is not blocked, e.g. by sending a FLUSH_START downstream.
MT safe.
| this |
the collectpads to use |
| flushing |
desired state of the pads |