- fc_writer.h/fc_writer.c: new framecache slot writer module
- Registers slot via POST /slots to framecache HTTP API on signal lock
- Opens shm file returned by API (O_RDWR + mmap MAP_SHARED)
- fc_writer_write(): atomic write_cursor advance + sem_post per frame
- fc_writer_close(): DELETE /slots/:id + munmap + sem_close
- HTTP calls via raw POSIX sockets (no libcurl dependency)
- Parses host:port from FC_URL env var or --fc-url arg
- main.c changes:
- PortState gains slot_id, fc_url, fc_writer fields
- --fc-url CLI arg + FC_URL env var (default http://localhost:7435)
- On signal lock: fc_writer_open() before thread launch;
falls back to FIFO if framecache unreachable (fc_writer == NULL)
- video_thread: shm path primary (fc_writer != NULL),
FIFO path fallback (fc_writer == NULL or LEGACY_FIFO=1)
- Format JSON now includes slot_id field for node-agent consumption
- Cleanup: fc_writer_close() before VHD_CloseBoardHandle
- CMakeLists.txt:
- Add fc_writer.c to build
- Link rt (shm_open, sem_open)
- LEGACY_FIFO option (OFF by default) for nodes without framecache
Audio thread unchanged — audio stays in FIFO (shm audio is roadmap).
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