libsstvenc: A simple SSTV encoder library in C.

THIS PROJECT IS A WORK-IN-PROGRESS.

The idea of this project is to provide a reasonable quality SSTV encoder implementation in C for use in custom SSTV applications.

• Source code: https://github.com/sjlongland/libsstvenc or https://codeberg.org/sjlongland/libsstvenc
• Documentation: https://static.vk4msl.com/projects/libsstvenc/

SSTV Modes

Implemented modes:

• Robot 8, 12 and 24 monochrome modes
• Robot 36 and 72 colour modes
• Scottie S1, S2 and DX
• Martin M1 and M2
• Pasokon P3, P5 and P7
• PD-50, PD-90, PD-120, PD-160, PD-180, PD-240 and PD-290
• Wraase SC-2 60, 120 and 180

Future possible modes

• Robot 24 Colour
• Martin M3, M4

Maybe some of the exotic modes supported by MMSSTV and QSSTV, if specifications can be found for them?

Not in scope

• HamDRM digital SSTV: this is basically a file transfer mechanism using an adapted form of Digital Radio Mondiale, much more complex OFDM transmission system. It'd be nice to have, but should be made into its own project.

Current work:

Packaging

Right now there's just a top-level Makefile which can compile a shared object library. It's pretty sparse. As things mature, it would be good to offer .deb packages for amd64, arm64 and armhf platforms, perhaps .rpm packages too.

A CLI application that can put the library through its paces more sophisticated than the example png-to-sstv.c distributed will probably be the next focus.

Fixing timing issues

After recent work, many of the modes are working as they should:

• Robot monochrome modes are basically spot on, save some offset issues which could just be receiver-related.
• Robot colour modes work, sometimes with an offset and some colour alignment, but again re-playing the same recording seems to generate a "better" image, so this could just be the decoder.
• Scottie S1 is slanted (forward-lean), worse in slowrx than in QSSTV.
• Scottie S2 is basically fine, save an offset to the right.
• Scottie DX seems spot on.
• Martin M1 and M2 are fine, save a small offset.
• Pasokon P3 is basically spot on, P5 has a small offset, P7 has a slight backward slant.
• PD modes seem to be fine aside from an offset to the right in some cases.
• Wraase SC-2: 120 mode has a slight forward-slant, 180 mode has a slight offset.

Still working on issues as I find them, but we're a lot closer now.

Platform/OS support

Tier 1

These are platforms I use regularly for this application and/or I use to directly test and develop this software.

• Debian GNU/Linux arm64 (Raspbian 64-bit)
• Gentoo Linux amd64

Tier 2

These are platforms I have access to, and can dig out and run tests on, but don't use regularly, so will see less frequent testing (or may be completely untested).

• Red Hat-derived Linux distributions
• Debian/Ubuntu amd64, armhf, armel, i386
• AlpineLinux amd64, arm64, i386
• Other Linux distributions (e.g. Slackware, Arch)
• DragonFlyBSD amd64
• FreeBSD amd64, arm64, armhf, i386
• NetBSD amd64, arm64, armhf, i386
• OpenBSD amd64, arm64, i386, mips64el
• Other BSD variants
• Apple MacOS X 10.6 amd64

Tier 3

These are platforms I do not have access to and thus require feedback from people who use those platforms. Patches for these platforms are accepted on the proviso the patches do not break Tier 1 or Tier 2 platforms, or make maintenance cumbersome.

• Apple MacOS X later than 10.6 or platforms other than amd64 (e.g. arm64 and ppc64)
• Microsoft Windows