【owt】erzio's handler and pipeline

• 【owt】erzio的PipelineBase::addService

• licode learning erizo chapter – the master of Pipeline_handle analyzed it very carefully:

• Summary from the master: The handler of erizo's pipeline is responsible for the actual data processing, and connects it in series through the processing link.

• The master also drew the basic class diagram:

pipeline is responsible for reading and writing data packets and processing data packets

• create:

  static Ptr create() {
   
    
    
    return std