Library parameters on gcc invocation about ffmpeg-libav-tutorial

[ginaluca]

Hi @leandromoreira , I tried the make run_hello command and the docker image executes smoothly, nice job.
Although I guess going through the pain of compilation is part of the process of learning ffmpeg :)

[xultz]

Hi gianluca, thank you for your tip. I compiled the code on Ubuntu 18.04 with ffmpeg compiled from source (3.4.2) and I had to modify the Makefile line according to your suggestion, and I had to add the -lm -lpthread -ldl -lswresample switches in order to compile and run it.

[retokromer]

with ffmpeg compiled from source (3.4.2)

Out of curiosity, is there any reason why you do not use 4.0?

[leandromoreira]

@ginaluca I did a docker compiler/runner can you try it out and see if any errors will show up.