Compiling on Ubuntu, problems with linking avcodec

[bryanlyon]

I'm compiling on Ubuntu using ffmpeg 3.4.6 I get

/usr/bin/ld: ../video_framework/libvideo_framework.a(video_reader_unit.cpp.o): undefined reference to symbol 'avcodec_open2@@LIBAVCODEC_57'
//usr/lib/x86_64-linux-gnu/libavcodec.so.57: error adding symbols: DSO missing from command line

This is a linking problem, but I haven't been able to solve it myself. Any help would be appreciated. I do have libavcodec-dev installed.

Additionally, I've tried ffmpeg 4.0. Unfortunately it also errors out with the following.

video_segment/video_framework/video_writer_unit.cpp:174:30: error: ‘CODEC_FLAG_LOOP_FILTER’ was not declared in this scope
codec_context_->flags |= CODEC_FLAG_LOOP_FILTER | CODEC_FLAG_GLOBAL_HEADER;