I am directly writing my video decoder output data into port buffer and sending this port buffer to the IL Client or to the tunneled component as output buffer. But my algorithm may use that port buffer as a reference frame, i.e. algorithm may use the data in the port buffer even which(port buffer) is sent from the omx component to il client or to the tunneled component.
If a tunnel is set-up as read-only (see 3.3.11 ComponentTunnelRequest in IL 1.1.2), then individual buffers may be marked as read-only. This allows you to keep a reference to a buffer that is given to a tunnelled component.
A correction - in IL 1.1.2, you can only mark a tunnel as read-only, not individual buffers. For communication with an IL client, you can’t therefore (from my reading of the spec) achieve your use-case.