It will allow to refernce it as a whole without clunky macros.

Most of the changes have been automatically made with sed:

sed -i '
  s/-> *in_formats/->incfg.formats/g;
  s/-> *out_formats/->outcfg.formats/g;
  s/-> *in_channel_layouts/->incfg.channel_layouts/g;
  s/-> *out_channel_layouts/->outcfg.channel_layouts/g;
  s/-> *in_samplerates/->incfg.samplerates/g;
  s/-> *out_samplerates/->outcfg.samplerates/g;
  ' src/libavfilter/*(.)