The channelLock parameter appears in audioBlockFormat only for the 'Objects' typeDefinition.

If the channelLock flag is set to 1 then the renderer will send the audio signal to the nearest (in terms of 3D position) channel or speaker position. A typical application for this is where the exact location of the object is not critical, but the need for un-processed reproduction of that signal takes priority.

The optional maxDistance attribute defines the radius r, 0 ≤ r ≤ 2, of a sphere around the object’s position. If one or more speakers exist in the defined sphere or on its surface, the object snaps to the nearest speaker. If maxDistance is undefined, a default value of infinity is assumed, meaning that the object should snap to the nearest of all speakers (unconditioned channelLock).