Sorry for insisting on this filepng part - but it was my work, and I dislike to ship broken feature! I actually tested Cinelerra git on Ubuntu Live DVD, and _16 bit_ pngs were broken there without it. It was as simple as 1) opening the video 2) setting project to rgba-float color format. 3) trying to save png (from non-black area of timeline) and set options to "with alpha, 16 bits". By default Cin adds encoded results into resources and on new tracks - you clearly can see it will be black/broken. 8-bits PNGs are OK. Ubuntu image I used: http://mirror.yandex.ru/ubuntu-cdimage/xubuntu/releases/18.04/release/ xubuntu-18.04.4-desktop-amd64.iso - 1.4 Gb Then I created 4 Gb file in tmpfs, formatted it with btrfs with compression, and booted Live image: guest@slax:/dev/shm$ wget http://mirror.yandex.ru/ubuntu-cdimage/xubuntu/releases/18.04/release/xubunt... --2020-03-25 13:55:42-- http://mirror.yandex.ru/ubuntu-cdimage/xubuntu/releases/18.04/release/xubunt... Распознаётся mirror.yandex.ru… 213.180.204.183, 2a02:6b8::183 Подключение к mirror.yandex.ru|213.180.204.183|:80... соединение установлено. HTTP-запрос отправлен. Ожидание ответа… 200 OK Длина: 1534459904 (1,4G) [application/octet-stream] Сохранение в: «xubuntu-18.04.4-desktop-amd64.iso» xubuntu-18.04.4-desktop-amd64.iso 100%[==============================================================================================================>] 1,43G 8,26MB/s за 6m 40s 2020-03-25 14:02:28 (3,66 MB/s) - «xubuntu-18.04.4-desktop-amd64.iso» сохранён [1534459904/1534459904] guest@slax:/dev/shm$ qemu-sy qemu-system-aarch64 qemu-system-i386 qemu-system-mips qemu-system-nios2 qemu-system-riscv64 qemu-system-sparc64 qemu-system-xtensaeb qemu-system-alpha qemu-system-lm32 qemu-system-mips64 qemu-system-or1k qemu-system-s390x qemu-system-tricore qemu-system-arm qemu-system-m68k qemu-system-mips64el qemu-system-ppc qemu-system-sh4 qemu-system-unicore32 qemu-system-cris qemu-system-microblaze qemu-system-mipsel qemu-system-ppc64 qemu-system-sh4eb qemu-system-x86_64 qemu-system-hppa qemu-system-microblazeel qemu-system-moxie qemu-system-riscv32 qemu-system-sparc qemu-system-xtensa guest@slax:/dev/shm$ qemu-system-x86_64 -m 2000 -display sdl,gl=on -soundhw es1370 -usb -cdrom xubuntu-18.04.4-desktop-amd64.iso qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate memory guest@slax:/dev/shm$ qemu-system-x86_64 -m 2000 -display sdl,gl=on -soundhw es1370 -usb -cdrom xubuntu-18.04.4-desktop-amd64.iso guest@slax:/dev/shm$ qemu-system-x86_64 -m 2000 -display sdl,gl=on -soundhw es1370 -usb -cdrom xubuntu-18.04.4-desktop-amd64.iso -enable-kvm -smp 3 guest@slax:/dev/shm$ qemu-system-x86_64 -m 2000 -display sdl,gl=on -soundhw es1370 -usb -cdrom xubuntu-18.04.4-desktop-amd64.iso -enable-kvm -smp 3 guest@slax:/dev/shm$ dd if=/dev/zero of=4Gb bs=1k count=4M 4194304+0 записей получено 4194304+0 записей отправлено 4294967296 байт (4,3 GB, 4,0 GiB) скопирован, 20,7155 s, 207 MB/s guest@slax:/dev/shm$ qemu-system-x86_64 -m 2000 -display sdl,gl=on -soundhw es1370 -usb -cdrom xubuntu-18.04.4-desktop-amd64.iso -enable-kvm -smp 4 -hda 4Gb WARNING: Image format was not specified for '4Gb' and probing guessed raw. Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted. Specify the 'raw' format explicitly to remove the restrictions. in just a hour I had compiled Cinelerra (by copying git tree from host BEFORE launching qemu) Note, in such mem-restricted VM you want to use zram (not default in this ubuntu flavor): as root modprobe zram echo 1000000000 > /sys/block/zram0/disksize mkswap /dev/zram0 swapon /dev/zram0 this will create 1Gb sized compressed swap in ram I even send email from this virtual setup, but it apparently was stuck in moderation due to size (over 750 kb). NOW, I found something really weird! Patch as attached worked on 64-bit Ubuntu, but for my system I *must* place this call to png_set_swap(png_ptr); differently, not before png_write_info(png_ptr, info_ptr); but AFTER! I actually left both there .... Still, this is something strange, I'll try to contact libpng author about this..... Also, I attach my current OpenCV tweaks - trim out unneeded stuff, fixing two typos, adding -stdc++11 line for my odd system. I still use opencv-20180401.tgz I also have two lame (mp3lame) patches, but will send them separately.