How to get the log output of the licode addons library

I am now debugging with Externaloutput.{h,cpp}, could anyone give me any hints on how to get the log output from the code.

Thank you very much !

BTW, I can get all the log output from the JS code and see some log outputs from other c++ code.
But there is no log output from

Let me answer my question:

I wrote a simple class to log the output to a file (say some file in /tmp folder). I also partially solved the video logging issue.
This line should add to the construction function:

setAudioSinkSSRC(1000000000 + getRandomValue(0, 999999999));
as well as other minor modifications in the ExternalOutput.cpp file.

Now, I can normally play back what I have logged.
Anyway, there are still bugs in ExternalOutput.cpp, since it forced the video should contains
both video and audio stream simultaneously. This is not the normal case, since sometimes
the stream only contains one of them.

Now, I am thinking how to add Data Channel to licode.
However, so fat, I am not familiar with the entire structure.

My intention is to extract the audio as input to speech recognition engine, and then send the recognition results back to the subscribers.