Port to modern FFmpeg, GCC 15, and updated liblo

[dnewcome]

Summary

I'm not sure if FreeJ dependencies can be satisfied on a modern Linux distro, at least not without a lot of wrangling. This PR fixes all compilation errors against modern toolchains and library versions, tested on Ubuntu with GCC 15, FFmpeg 7.1, and liblo from current package repositories.

Mostly Claude wrangling but some inspection and manual cajoling. I did a smoke test just by running some javascript files but it does compile cleanly and runs on Ubuntu 25.10. I ran the test script that was there but I don't think it tested much but maybe I just didn't look hard enough.

BTW this is a cool project, I can't believe I didn't know of it until now. I was using veejay on RPi4 and wasn't aware that there was something that predated even that. I started work on fast-vj with the goal of doing something similar to this but with modern shader architectures that can work on limited hardware like the RPi. I ended up using LuaJIT instead of JS with the hopes that it could drive significant interactivity logic without becoming a bottleneck.

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FFmpeg 7.x API migration

The largest body of work. FFmpeg has removed or deprecated many APIs over its 4.x–7.x releases that FreeJ relied on. Changes across src/video_layer.cpp, src/include/video_layer.h, src/ffdec.c, and src/context.cpp:

Struct changes

• AVPicture was removed in FFmpeg 5.0. All uses replaced with AVFrame, which carries the same data[] and linesize[] fields. rgba_picture and the frame FIFO now hold AVFrame * allocated with av_frame_alloc().

Allocation / buffer management

• avpicture_alloc() → av_frame_get_buffer()
• avpicture_free() → av_frame_unref() + av_free()
• avpicture_fill() → av_image_fill_arrays()
• avpicture_get_size() → av_image_get_buffer_size()
• avpicture_deinterlace() was removed with no direct replacement; the deinterlace path is stubbed out (it was off by default anyway)

Format / codec open sequence

• av_open_input_file() → avformat_open_input()
• av_find_stream_info() → avformat_find_stream_info()
• AVFormatParameters and url_set_interrupt_cb() removed; format options now passed via AVDictionary
• Codec contexts are no longer borrowed from AVStream::codec (deprecated). Each stream now gets its own context via avcodec_alloc_context3() + avcodec_parameters_to_context(), owned and freed by the layer
• avcodec_open() → avcodec_open2()
• avcodec_close() → avcodec_free_context() (closes and frees in one call)

Decode API

• avcodec_decode_video2() and avcodec_decode_audio3() replaced with the send/receive API: avcodec_send_packet() / avcodec_receive_frame()
• avcodec_get_frame_defaults() removed; replaced by av_frame_unref() semantics

Misc FFmpeg removals

• av_register_all() / avcodec_register_all() / avcodec_init() removed (codecs auto-register since FFmpeg 4.0)
• av_free_packet() → av_packet_unref()
• av_close_input_file() → avformat_close_input()
• avcodec_alloc_frame() → av_frame_alloc()
• dump_format() → av_dump_format()
• PIX_FMT_* → AV_PIX_FMT_*
• AVCodecContext::channels → AVCodecContext::ch_layout.nb_channels
• CODEC_TYPE_VIDEO → AVMEDIA_TYPE_VIDEO
• FF_B_TYPE / FF_I_TYPE → AV_PICTURE_TYPE_B / AV_PICTURE_TYPE_I

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GCC 15 / SpiderMonkey configure fixes

GCC 14+ promotes two previously-warning conditions to hard errors, breaking the bundled SpiderMonkey (lib/javascript) configure script:

• -Wimplicit-int is now an error. The configure script contained K&R-style main(){return(0);} in compiler probe programs. Fixed to int main(){return(0);}.
• -Wreturn-mismatch is now an error. Eight int main() test functions used bare return; with no value. Fixed to return 0;.
• Missing execute permissions on build/hcc, build/hcpp, and a dozen other helper scripts caused the SpiderMonkey configure to fail mid-run with "Permission denied". Execute bit restored on all affected files.

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liblo API update

osc_ctrl.cpp used the old lo_method_handler signature where the incoming-message argument was void *. Current liblo types this as lo_message. Additionally, lo_send_message_from() requires a lo_server (not a lo_server_thread); fixed by calling lo_server_thread_get_server().

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Housekeeping

• Added compile and test-driver to .gitignore — these are automake-generated helper scripts that get dropped into the project root by ./configure and don't belong in version control.

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Test environment

• OS: Ubuntu (Linux 6.17, x86_64)
• GCC 15.2
• FFmpeg 7.1.1
• liblo (current Ubuntu package)
• libSDL 1.2, libsdl-image 1.2
• SpiderMonkey (bundled, built statically)

./configure && make completes cleanly and the freej binary runs.