OK, now that both Andrea and Andrew think we should upgrade to flac 1.4.0, I will check it into GIT in the next couple of days. It did build on both Ubuntu 16 and Debian 11.0 (32-bit). The Debian initially failed on rendering but I must have done something wrong because I could not reproduce it.
More tests show results all over the place and some mirror what Andrea was seeing where compression level 5 is better than level 0. Times vary just doing the exact same tests again on the same computer/operating system but size consistent. Anyway listing them here just for showing.
x.wav file input:
** rendered 449 frames in 0.022 secs, 20409.091 fps / Size=438488 / Flac 1.3.2
** rendered 449 frames in 0.019 secs, 23631.579 fps / Size=430891 / Flac 1.4.0 Compression=0
** rendered 449 frames in 0.020 secs, 22450.000 fps / Size=416361 / Flac 1.4.0 Compression=5
** rendered 449 frames in 0.030 secs, 14966.667 fps / Size=412751 / Flac 1.4.0 Compression=8
Ubuntu 16 (no flac 1.3.2 comparison):
** rendered 2713 frames in 0.658 secs, 4123.100 fps / Size=11452512 / Flac 1.4.0 Compression=0
** rendered 2713 frames in 0.624 secs, 4347.756 fps / Size= 9466523 / Flac 1.4.0 Compression=5
** rendered 2713 frames in 1.335 secs, 2033.733 fps / Size= 9005632 / Flac 1.4.0 Compression=8
Debian 11.0 32-bit: (BTW: as Andrew already noted, the patches for the GUI also worked at 1.3.2.)
** rendered 2713 frames in 0.731 secs, 3771.354 fps / Size=9276506 / Flac 1.3.2 Compression=0
** rendered 2713 frames in 0.668 secs, 4061.377 fps / Size= 9541136 / Flac 1.3.2Compression=5
** rendered 2713 frames in 1.653 secs, 1641.258 fps / Size= 11452514 / Flac 1.3.2 Compression=8
** rendered 2713 frames in 0.601 secs, 4514.143 fps / Size=11452512 / Flac 1.4.0 Compression=0
** rendered 2713 frames in 0.767 secs, 3537.386 fps / Size=11452512 / Flac 1.4.0 Compression=0
** rendered 2713 frames in 0.772 secs, 3514.249 fps / Size= 9466515 / Flac 1.4.0 Compression=5
** rendered 2713 frames in 1.864 secs, 1455.472 fps / Size= 9005623 / Flac 1.4.0 Compression=8