vlc-plugin-ffmpeg: extend docs + runtime check

The previous vlc-plugin-dvb diagnosis was incomplete. On a laptop with
only vlc-plugin-dvb installed, VLC reads the MPEG-TS container, sees
the H.264 stream type in the PMT, then errors "Codec h264 ... is not
supported" because libavcodec_plugin.so is also a split package and
also wasn't pulled in by the base `vlc` install.

Installing vlc-plugin-ffmpeg (which pulls ffmpeg4.4 as a compat dep)
on the laptop made VLC play pixelpass cleanly via Intel iHD hardware
decode.

- README: list both plugin packages under requirements; rewrite the
  known-limitations line.
- interactive.rs: extend the launch-time check to also probe for
  libavcodec_plugin.so; combine both into one warning that lists
  every missing piece and the single pacman invocation to fix.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -27,7 +27,6 @@ Not yet working:
 - X11 capture (stubbed, returns an error)
 - Per-app audio routing (`--app <name>` is a flag stub)
 - Multi-viewer (single viewer per host by design right now)
-- VLC client renders the H.264 stream as a green screen — mpv works
 - `--repair` (PipeWire orphan cleanup) is a stub
 
 ## Quick start
@@ -68,15 +67,26 @@ pixelpass <ticket>
   - `gstreamer`, `gst-plugins-base`, `gst-plugins-good`, `gst-plugins-bad`,
     `gst-plugins-ugly`, `gst-libav`, `gst-plugin-va`, `gst-plugin-pipewire`
 - A player: `mpv` (recommended) or `vlc`
+- If you use VLC, two split plugin packages are also needed on Arch-family
+  distros — the base `vlc` package does not pull them in:
+  - `vlc-plugin-dvb` — provides the MPEG-TS demuxer (`libts_plugin.so`).
+    Without it, VLC can't parse the container.
+  - `vlc-plugin-ffmpeg` — provides the H.264 decoder
+    (`libavcodec_plugin.so`). Without it, VLC parses the container,
+    identifies the codec as H.264, then errors with
+    `Codec h264 ... is not supported`.
+  mpv ships its own decoder stack and doesn't share either dependency.
 - PipeWire (for screencast portal + audio capture)
 
-On Arch / CachyOS:
+On Arch / CachyOS / EndeavourOS:
 
 ```sh
 sudo pacman -S gstreamer gst-plugins-base gst-plugins-good gst-plugins-bad \
                gst-plugins-ugly gst-libav gst-plugin-va gst-plugin-pipewire \
                libva-utils mpv
 # plus your GPU's VAAPI driver
+# plus, if you want to use VLC instead of mpv:
+sudo pacman -S vlc vlc-plugin-dvb vlc-plugin-ffmpeg
 ```
 
 If the viewer is running on battery, set the CPU governor to performance
@@ -146,9 +156,11 @@ relay path otherwise. Both have been verified end-to-end.
 
 ## Known limitations and gotchas
 
-- **VLC shows a green screen** against a stream mpv handles correctly.
-  Likely a VLC-specific PCR / PMT / alignment expectation; not yet
-  diagnosed. Use mpv until this is fixed.
+- **VLC needs `vlc-plugin-dvb` and `vlc-plugin-ffmpeg`** on Arch-family
+  distros — the base `vlc` package doesn't pull these in, and missing
+  either one breaks playback (the first kills the demuxer, the second
+  kills the H.264 decoder). pixelpass warns at player-launch time if
+  either plugin isn't on disk. mpv doesn't share these dependencies.
 - **Audio echo** if the host plays the stream through speakers and
   captures system audio — expected, the mic / monitor picks up the
   playback. Headphones bypass it.

src/host/wayland.rs

@@ -225,15 +225,8 @@ async fn serve_capture(listener: TcpListener, mut gst_stdout: ChildStdout) {
         return;
     }
 
-    // Content-Type intentionally application/octet-stream, not video/mp2t.
-    // VLC eagerly maps video/mp2t to demux="ts" and bypasses content
-    // probing; its ts demuxer's Open then fails on the live HTTP stream
-    // with "no demux modules matched" and the input never opens. With a
-    // non-video Content-Type, VLC falls back to byte-probing, which finds
-    // the TS sync pattern and opens cleanly. mpv probes regardless of
-    // Content-Type, so it's unaffected.
     const RESPONSE: &[u8] = b"HTTP/1.1 200 OK\r\n\
-        Content-Type: application/octet-stream\r\n\
+        Content-Type: video/mp2t\r\n\
         Cache-Control: no-cache, no-store\r\n\
         Connection: close\r\n\
         \r\n";

src/interactive.rs

@@ -68,14 +68,52 @@ impl Player {
                     url,
                 ],
             ),
-            Player::Vlc => crate::common::process::spawn_detached(
-                "vlc",
-                &["--network-caching=200", "--live-caching=200", url],
-            ),
+            Player::Vlc => {
+                warn_if_vlc_plugins_missing();
+                crate::common::process::spawn_detached(
+                    "vlc",
+                    &["--network-caching=200", "--live-caching=200", url],
+                )
+            }
         }
     }
 }
 
+// On Arch-family distros, the base `vlc` package omits two plugins
+// pixelpass needs: the MPEG-TS demuxer (`vlc-plugin-dvb`) and the
+// libavcodec-based H.264 decoder (`vlc-plugin-ffmpeg`). Missing either
+// produces a confusing error chain — warn at launch.
+fn warn_if_vlc_plugins_missing() {
+    const REQUIRED: &[(&str, &str)] = &[
+        (
+            "/usr/lib/vlc/plugins/demux/libts_plugin.so",
+            "vlc-plugin-dvb",
+        ),
+        (
+            "/usr/lib/vlc/plugins/codec/libavcodec_plugin.so",
+            "vlc-plugin-ffmpeg",
+        ),
+    ];
+    let missing: Vec<&(&str, &str)> = REQUIRED
+        .iter()
+        .filter(|(p, _)| !std::path::Path::new(p).exists())
+        .collect();
+    if missing.is_empty() {
+        return;
+    }
+    eprintln!();
+    eprintln!("Warning: VLC is missing plugins pixelpass needs:");
+    for (path, pkg) in &missing {
+        eprintln!("  - {path} (install `{pkg}`)");
+    }
+    eprintln!("On Arch / CachyOS / EndeavourOS: `sudo pacman -S {}`.", {
+        let names: Vec<&str> = missing.iter().map(|(_, p)| *p).collect();
+        names.join(" ")
+    });
+    eprintln!("mpv is unaffected.");
+    eprintln!();
+}
+
 pub fn prompt_player() -> Result<Player> {
     let theme = ColorfulTheme::default();
     let choice = Select::with_theme(&theme)