Dear Sebastian, I'm referring to https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1004794.
You've reported a bunch of compiling errors. AFAIK these are due to FFmpeg reorganizing their header files. Nowadays its required to explicitly include "avcodec/libavcodec.h" whereas in previous versions it was sufficient to include "avformat/libavformat.h" (which in turn included "avcodec/libavcodec.h").
Please note that bs1770gain-0.8.4.tar.gz follows the requirement changed by FFmpeg out of the blue.
Best regards Peter
