Both sites default to site_id=0; gateway must rewrite site_id in
announcements and protocol messages crossing the boundary. site_id=0
on a cross-site link is a gateway protocol error.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Covers all layers: TCP → transport frame → message type dispatcher →
payload schemas. Documents frame format (6-byte header), all message
types, STREAM_OPEN/CLOSE lifecycle, codec/pixel_format/origin tables,
stream events, and discovery announcement wire format.
Also fixes stale channel_id reference in audio section of architecture.md.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Modules (src/modules/):
- common/error: App_Error struct with structured detail union, error codes,
app_error_print(); designed for future upgrade to preprocessor-generated
location codes
- media_ctrl: media device enumeration, topology query (entities/pads/links),
link enable/disable via Media Controller API (/dev/media*)
- v4l2_ctrl: control enumeration (with menu item fetching), get/set via
V4L2 ext controls API, device discovery (/dev/video*)
All modules use -std=c11 -D_GNU_SOURCE, build artifacts go to build/ only.
Kernel-version-dependent constants guarded with #ifdef + #warning.
CLI drivers (dev/cli/):
- media_ctrl_cli: list, info, topology, set-link subcommands
- v4l2_ctrl_cli: list, controls, get, set subcommands
Docs (docs/cli/):
- media_ctrl_cli.md and v4l2_ctrl_cli.md with usage, examples, and
context within the video routing system
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
