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Old 31st May 2019, 05:39   #11  |  Link
qyot27's Avatar
Join Date: Nov 2005
Location: Florida
Posts: 1,268
Since I've now hammered out the kinks (hopefully), I'm able to answer this based on actually cross-compiling VapourSynth instead of using gendef on Windows dlls.
Originally Posted by jackoneill View Post
By the way, did you need to patch VapourSynth to accomplish this?
Not really. Most of the weirdness is in how to handle Python (it still needs to be gendeffed, et al.). VapourSynth itself has only three issues at play here:
  • src/vsscript/vsscript.cpp has an include of Windows.h that trips up cross-compiles due to case sensitivity.
  • No matter what I tried, I couldn't force NASM to recognize the multilib MinGW-w64 environment and actually compile 32-bit objects, so I have to force-override the Makefile to compile the correct object format.
  • The Requires.private invocation of python in vapoursynth-script.pc screws up FFmpeg's configure tests; Libs.private does work as expected.
  • A possible fourth issue is whether there's a case for including -lstdc++ in the .pc file's Libs(.private) stuff (it's not a problem when a bunch of other external libraries are enabled, since one/several of them pull in -lstdc++, but a 'simple' build of FFmpeg with VapourSynth and AviSynth as the only enabled external libraries fails unless --extra-libs is used to provide libstdc++ as detailed way earlier in this thread). Or whether a Cflags.private entry should be added for pkgconf users so -DVS_CORE_EXPORTS can be used only in the case of static linking. Essentially, this 'point' basically is just bikeshedding.

The entire process is documented here (link goes directly to the VapourSynth section of the guide):

One distinction is that when I'd tested with using gendef to handle VapourSynth too, I could get FFmpeg to link to it, but mpv refused to link to libavformat. gendeffing only Python and then cross-compiling VapourSynth like any other library results in both FFmpeg and mpv being able to link to it (importantly, mpv being able to directly play back scripts this way).

32-bit and 64-bit FFmpeg and mpv with static VapourSynth

Said binaries include *both* VS demuxers. The upstream demuxer is still 'vapoursynth', and the other one is 'vapoursynth_alt'. It's easy to tell them apart because they return different data types as input: '-f vapoursynth' returns wrapped_avframe, '-f vapoursynth_alt' returns rawvideo. The upstream demuxer also doesn't honor relative file paths across directories (in just FFMS2? maybe in general?), while the alt demuxer does.

Last edited by qyot27; 31st May 2019 at 16:47.
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