As usual I was the one who was missing the point: I was using ffmpeg's
flac preset and not CinGG's internal engine. Sorry.
Using the latter the "compression" field is there and is usable. The
results are as follows:


flac-1.3 (appimage)

** rendered 9063 frames in 0.646 secs, 14029.412 fps, size 18.2 MiB


flac-1.4 (build with the 4 patches)

default (0): ** rendered 9063 frames in 0.846 secs, 10712.766 fps, size 18.1 MiB

(4) : ** rendered 9063 frames in 0.843 secs, 10750.890 fps, size 18.1 MiB

(8) : ** rendered 9063 frames in 0.843 secs, 10750.890 fps, size 18.1 MiB


It seems that the compression setting is not working, I always get the
same result.