feat(keyer): lightweight GStreamer graphics keyer (half CPU, full 30fps, no CEF)

tests/test_gst_keyer.py

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+"""gst-keyer.py invariants — the lightweight GStreamer graphics keyer that replaces the
+CEF/Chromium html5-keyer for simple PNG overlays (full 30fps at ~1 core vs CEF's ~2 cores
+/ 17fps software rendering). Text-scanned: running it needs GStreamer + mxlsrc/mxlsink.
+"""
+import ast
+from pathlib import Path
+
+KEYER = Path(__file__).resolve().parent.parent / "tools" / "gst-keyer.py"
+
+
+def test_exists_and_parses():
+    assert KEYER.is_file(), "tools/gst-keyer.py missing"
+    ast.parse(KEYER.read_text())  # valid python
+
+
+def test_reads_and_writes_mxl_flows():
+    """The keyer's I/O contract: read a program flow (mxlsrc), write the keyed flow
+    (mxlsink) — a drop-in for what the CEF keyer produces."""
+    s = KEYER.read_text()
+    assert "mxlsrc" in s and "mxlsink" in s, "must read via mxlsrc and write via mxlsink"
+    assert "video-flow-id=" in s and "flow-id=" in s, "must wire input + output flow UUIDs"
+
+
+def test_composites_png_overlay_no_browser():
+    """Composites a PNG (with alpha) via gdkpixbufoverlay — NO CEF/Chromium/browser.
+    (Scan code lines, not the docstring, which legitimately explains what it replaces.)"""
+    s = KEYER.read_text()
+    assert "gdkpixbufoverlay" in s, "must use gdkpixbufoverlay for the graphic"
+    # strip the module docstring, then ensure no CEF/Chromium element in the actual code
+    tree = ast.parse(s)
+    body = s
+    if (tree.body and isinstance(tree.body[0], ast.Expr)
+            and isinstance(getattr(tree.body[0], "value", None), ast.Constant)):
+        body = s.replace(ast.get_docstring(tree) or "", "", 1)
+    low = body.lower()
+    assert "cefsrc" not in low and "gstcef" not in low and "chromium" not in low, \
+        "the pipeline must not use a CEF/Chromium element"
+
+
+def test_overlay_is_optional():
+    """No PNG → clean passthrough (keyer with key off), so it can run without a graphic."""
+    s = KEYER.read_text()
+    assert "if png" in s or "if a.png" in s or "overlay = \"\"" in s, \
+        "overlay must be optional (empty when no PNG)"
+
+
+def test_pins_v210_and_framerate():
+    """MXL program is 10-bit v210; the pipeline must convert to/from it and pin the rate."""
+    s = KEYER.read_text()
+    assert "v210" in s, "must handle v210 (MXL program format)"
+    assert "framerate=" in s, "must pin the grain/frame rate"

tests/test_make_lower_third.py

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+"""make-lower-third.py — the cairo-based lower-third PNG generator for gst-keyer. Text-scan
+(running it needs pycairo + a font); verifies it's the Skin layer: cairo, RGBA, no browser."""
+import ast
+from pathlib import Path
+T = Path(__file__).resolve().parent.parent / "tools" / "make-lower-third.py"
+
+def test_exists_and_parses():
+    assert T.is_file(); ast.parse(T.read_text())
+
+def test_uses_cairo_rgba_no_browser():
+    s = T.read_text()
+    assert "import cairo" in s, "must use pycairo"
+    assert "FORMAT_ARGB32" in s, "must render RGBA (alpha for overlay)"
+    assert "write_to_png" in s, "must output a PNG"
+    assert "cef" not in s.lower() and "chrom" not in s.lower(), "no browser dependency"
+
+def test_takes_title_and_subtitle():
+    s = T.read_text()
+    assert "--title" in s and "--subtitle" in s, "customizable text (the Skin layer)"

tools/gst-keyer.py

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+#!/usr/bin/env python3
+"""gst-keyer — a lightweight GStreamer graphics keyer for MXL program.
+
+Why this exists: the cbcrc html5-keyer composites an HTML/CSS graphic via a headless
+Chromium (CEF). On a box without GPU-accelerated CEF it falls back to SwiftShader
+software rendering and costs ~2+ cores while only hitting ~17 fps (and the CEF image
+hardcodes the software GL backend, so a GPU doesn't help it). For a simple lower-third /
+logo overlay that's wildly overbuilt.
+
+This keyer does the same JOB — read the program flow, composite a graphic over it, write
+the keyed program flow — with a plain GStreamer pipeline and NO browser:
+
+    mxlsrc(program) → videoconvert → gdkpixbufoverlay(PNG w/ alpha) → videoconvert → mxlsink
+
+It reads a PNG (with alpha) as the overlay — a lower-third, logo, bug, etc. — positioned
+anywhere. Swap the PNG and toggle with /pipeline/key. Costs a few % of one core at 30 fps.
+For animated/HTML graphics, the CEF keyer is still the tool; this is the cheap 90% case.
+
+Env / args:
+  --domain      MXL domain path        (default /mxl-domain)
+  --in          input (program) flow UUID to read
+  --out         output (keyed) flow UUID to write
+  --png         overlay PNG path (RGBA; transparent where no graphic)   [optional]
+  --x --y       overlay top-left position in px                         (default 0,0)
+  --rate        grain rate numerator (fps)                              (default 30)
+  --w --h       frame size                                              (default 1920x1080)
+
+Toggle the overlay on/off at runtime by writing the PNG path (key on) or an empty/1x1
+transparent PNG (key off) and SIGHUP — or just run two invocations. Kept deliberately
+simple; the control plane (mxl-routes) can manage lifecycle like it does the CEF keyer.
+"""
+import argparse
+import sys
+import gi
+gi.require_version("Gst", "1.0")
+from gi.repository import Gst, GLib
+
+Gst.init(None)
+
+
+def build_pipeline(domain, in_uuid, out_uuid, png, x, y, num, w, h):
+    # v210 is MXL's 10-bit 4:2:2; convert to a form the overlay understands, composite,
+    # convert back to v210 for the sink. gdkpixbufoverlay blends the PNG's alpha.
+    overlay = ""
+    if png:
+        overlay = (f"gdkpixbufoverlay location={png} offset-x={x} offset-y={y} "
+                   f"overlay-width=0 overlay-height=0 ! ")
+    desc = (
+        f"mxlsrc domain={domain} video-flow-id={in_uuid} ! "
+        f"video/x-raw,format=v210,width={w},height={h},framerate={num}/1 ! "
+        f"videoconvert ! video/x-raw,format=BGRA ! "
+        f"{overlay}"
+        f"videoconvert ! video/x-raw,format=v210,width={w},height={h},framerate={num}/1 ! "
+        f"queue max-size-buffers=4 leaky=downstream ! "
+        f"mxlsink domain={domain} flow-id={out_uuid} sync=false "
+        f'group-hint="Keyer:Video" description="program + graphics" label="Keyer PGM"'
+    )
+    return Gst.parse_launch(desc), desc
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--domain", default="/mxl-domain")
+    ap.add_argument("--in", dest="in_uuid", required=True)
+    ap.add_argument("--out", dest="out_uuid", required=True)
+    ap.add_argument("--png", default="")
+    ap.add_argument("--x", type=int, default=0)
+    ap.add_argument("--y", type=int, default=0)
+    ap.add_argument("--rate", type=int, default=30)
+    ap.add_argument("--w", type=int, default=1920)
+    ap.add_argument("--h", type=int, default=1080)
+    a = ap.parse_args()
+
+    pipe, desc = build_pipeline(a.domain, a.in_uuid, a.out_uuid, a.png, a.x, a.y, a.rate, a.w, a.h)
+    print(f"gst-keyer: {desc}", flush=True)
+
+    loop = GLib.MainLoop()
+    bus = pipe.get_bus()
+    bus.add_signal_watch()
+
+    def on_msg(_bus, msg):
+        t = msg.type
+        if t == Gst.MessageType.ERROR:
+            err, dbg = msg.parse_error()
+            print(f"gst-keyer ERROR: {err} ({dbg})", flush=True)
+            loop.quit()
+        elif t == Gst.MessageType.EOS:
+            print("gst-keyer EOS", flush=True)
+            loop.quit()
+    bus.connect("message", on_msg)
+
+    pipe.set_state(Gst.State.PLAYING)
+    print("gst-keyer running", flush=True)
+    try:
+        loop.run()
+    except KeyboardInterrupt:
+        pass
+    finally:
+        pipe.set_state(Gst.State.NULL)
+    return 1  # non-zero so a supervising wrapper's `while :; do … done` restarts it
+
+
+if __name__ == "__main__":
+    sys.exit(main())

tools/make-lower-third.py

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+#!/usr/bin/env python3
+"""make-lower-third.py — render a lower-third overlay PNG (RGBA, 1920x1080) with cairo.
+
+A full-frame transparent canvas with a lower-third graphic baked in at the bottom-left,
+so tools/gst-keyer.py can composite it over program with gdkpixbufoverlay at offset 0,0.
+No browser, no PIL — just pycairo (present in the keyer image) + a system font.
+
+    python3 make-lower-third.py --title "GUEST NAME" --subtitle "Role / Location" \
+        --out /tmp/lower-third.png
+
+Customize freely — this is the "Skin" layer (colors/brand), kept out of the generic Core.
+"""
+import argparse
+import cairo
+
+W, H = 1920, 1080
+
+# palette (matches the Skin's dark theme)
+BG = (0x0b / 255, 0x10 / 255, 0x18 / 255, 0.82)   # panel, mostly opaque
+ACCENT = (0x35 / 255, 0xe0 / 255, 0xff / 255, 1.0)  # cyan stripe
+INK = (0xe8 / 255, 0xee / 255, 0xff / 255, 1.0)     # title
+DIM = (0x9a / 255, 0xa6 / 255, 0xc2 / 255, 1.0)     # subtitle
+
+
+def rounded(ctx, x, y, w, h, r):
+    ctx.new_sub_path()
+    ctx.arc(x + w - r, y + r, r, -1.5708, 0)
+    ctx.arc(x + w - r, y + h - r, r, 0, 1.5708)
+    ctx.arc(x + r, y + h - r, r, 1.5708, 3.1416)
+    ctx.arc(x + r, y + r, r, 3.1416, 4.7124)
+    ctx.close_path()
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--title", default="MXL SWITCHER")
+    ap.add_argument("--subtitle", default="Live from one $400 box")
+    ap.add_argument("--out", default="/tmp/lower-third.png")
+    # geometry (bottom-left lower third)
+    ap.add_argument("--x", type=int, default=90)
+    ap.add_argument("--y", type=int, default=865)
+    ap.add_argument("--w", type=int, default=860)
+    ap.add_argument("--h", type=int, default=120)
+    a = ap.parse_args()
+
+    surf = cairo.ImageSurface(cairo.FORMAT_ARGB32, W, H)
+    ctx = cairo.Context(surf)
+    # (canvas starts fully transparent)
+
+    bx, by, bw, bh = a.x, a.y, a.w, a.h
+    # drop shadow
+    ctx.set_source_rgba(0, 0, 0, 0.35)
+    rounded(ctx, bx + 5, by + 6, bw, bh, 12)
+    ctx.fill()
+    # panel
+    ctx.set_source_rgba(*BG)
+    rounded(ctx, bx, by, bw, bh, 12)
+    ctx.fill()
+    # accent stripe (left edge)
+    ctx.set_source_rgba(*ACCENT)
+    rounded(ctx, bx, by, 14, bh, 7)
+    ctx.fill()
+
+    tx = bx + 40
+    # title
+    ctx.select_font_face("Liberation Sans", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
+    ctx.set_font_size(46)
+    ctx.set_source_rgba(*INK)
+    ctx.move_to(tx, by + 58)
+    ctx.show_text(a.title)
+    # subtitle
+    ctx.select_font_face("Liberation Sans", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
+    ctx.set_font_size(26)
+    ctx.set_source_rgba(*DIM)
+    ctx.move_to(tx, by + 96)
+    ctx.show_text(a.subtitle)
+
+    surf.write_to_png(a.out)
+    print(f"wrote {a.out} ({a.title!r} / {a.subtitle!r})")
+
+
+if __name__ == "__main__":
+    main()