the sink #GstPad that performed the chain.
the parent of pad. If the #GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-%NULL and remain valid during the execution of this function.
the #GstBuffer that is chained, not %NULL.
A function that will be called on sinkpads when chaining buffers. The function typically processes the data contained in the buffer and either consumes the data or passes it on to the internally linked pad(s).
The implementer of this function receives a refcount to
bufferand should gst_buffer_unref() when the buffer is no longer needed.When a chain function detects an error in the data stream, it must post an error on the bus and return an appropriate #GstFlowReturn value.