the probe mask
#GstPadProbeCallback that will be called with notifications of the pad state
user data passed to the callback
#GDestroyNotify for user_data
an id or 0 if no probe is pending. The id can be used to remove the probe with gst_pad_remove_probe(). When using GST_PAD_PROBE_TYPE_IDLE it can happen that the probe can be run immediately and if the probe returns GST_PAD_PROBE_REMOVE this functions returns 0.
MT safe.
Be notified of different states of pads. The provided callback is called for every state that matches @mask.
Probes are called in groups: First GST_PAD_PROBE_TYPE_BLOCK probes are called, then others, then finally GST_PAD_PROBE_TYPE_IDLE. The only exception here are GST_PAD_PROBE_TYPE_IDLE probes that are called immediately if the pad is already idle while calling gst_pad_add_probe(). In each of the groups, probes are called in the order in which they were added.