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>

src/interactive.rs

@@ -69,7 +69,7 @@ impl Player {
                 ],
             ),
             Player::Vlc => {
-                warn_if_vlc_ts_demuxer_missing();
+                warn_if_vlc_plugins_missing();
                 crate::common::process::spawn_detached(
                     "vlc",
                     &["--network-caching=200", "--live-caching=200", url],
@@ -79,22 +79,39 @@ impl Player {
     }
 }
 
-// VLC's MPEG-TS demuxer ships in a separate package on Arch / CachyOS
-// (`vlc-plugin-dvb`). Without it VLC falls through to the PS demuxer
-// and shows a green screen.
-fn warn_if_vlc_ts_demuxer_missing() {
-    const TS_DEMUX_PLUGIN: &str = "/usr/lib/vlc/plugins/demux/libts_plugin.so";
-    if !std::path::Path::new(TS_DEMUX_PLUGIN).exists() {
-        eprintln!();
-        eprintln!(
-            "Warning: VLC's MPEG-TS demuxer plugin ({TS_DEMUX_PLUGIN}) is missing."
-        );
-        eprintln!(
-            "         On Arch / CachyOS, install `vlc-plugin-dvb`. Without it,"
-        );
-        eprintln!("         VLC will show a green screen. mpv is unaffected.");
-        eprintln!();
+// 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> {