Add MPS demuxer and FFmpeg H.264 video decode

- MpsDemuxer parses MPEG-PS packs (0x1BA) into video (0x1E0-0x1EF) and
  audio (0x1BD) PES packets with PTS/DTS at the 90kHz clock.
- VideoDecoder decodes Annex-B H.264 via JavaCPP FFmpeg 8.1.2, splitting
  the stream into access units (one slice NAL per packet) so each send
  yields a frame.
- CLI 'decode' command dumps frame metadata (720x480 YUVJ420P).
- Validated against Batman Begins: 72 frames decoded.

cli/build.gradle.kts

@@ -9,7 +9,6 @@ java {
 }
 
 application {
-    mainModule = "dev.quoije.umd.cli"
     mainClass = "dev.quoije.umd.cli.Main"
 }
 

cli/src/main/java/dev/quoije/umd/cli/Main.java

@@ -3,10 +3,12 @@ package dev.quoije.umd.cli;
 
 import dev.quoije.umd.iso.UmdIsoFile;
 import dev.quoije.umd.iso.UmdIsoReader;
+import dev.quoije.umd.media.VideoDecoder;
 import dev.quoije.umd.mps.MpsDemuxer;
 import dev.quoije.umd.playlist.Playlist;
 import dev.quoije.umd.sfo.Sfo;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
@@ -15,7 +17,7 @@ import java.util.Map;
 /** Command-line front-end for the UMD player library. */
 public final class Main {
 
-    private static final String USAGE = "usage: umdplayer dump <image.iso>\n       umdplayer mps <image.iso> <streamName>";
+    private static final String USAGE = "usage: umdplayer dump <image.iso>\n       umdplayer mps <image.iso> <streamName>\n       umdplayer decode <image.iso> <streamName>";
 
     private Main() {
     }
@@ -31,6 +33,7 @@ public final class Main {
             exitCode = switch (args[0]) {
                 case "dump" -> dump(requireArg(args, 1));
                 case "mps" -> mps(requireArg(args, 1), requireArg(args, 2));
+                case "decode" -> decode(requireArg(args, 1), requireArg(args, 2));
                 case "help", "--help", "-h" -> {
                     System.out.println(USAGE);
                     yield 0;
@@ -186,6 +189,52 @@ public final class Main {
         return 0;
     }
 
+    private static int decode(String imagePath, String streamName) throws IOException {
+        try (UmdIsoReader iso = new UmdIsoReader(Path.of(imagePath));
+             MpsDemuxer demuxer = MpsDemuxer.open(iso, streamName)) {
+
+            ByteArrayOutputStream video = new ByteArrayOutputStream();
+            int packets = 0;
+            int videoPackets = 0;
+            while (packets < 300) {
+                MpsDemuxer.Packet pkt = demuxer.nextPacket();
+                if (pkt == null) {
+                    break;
+                }
+                packets++;
+                if (!pkt.isVideo()) {
+                    continue;
+                }
+                video.write(pkt.payload(), 0, pkt.payload().length);
+                videoPackets++;
+            }
+
+            byte[] annexB = video.toByteArray();
+
+            try (VideoDecoder decoder = new VideoDecoder()) {
+                decoder.feedAnnexB(annexB);
+                decoder.flush();
+
+                int frames = 0;
+                VideoDecoder.Frame frame;
+                while ((frame = decoder.receive()) != null) {
+                    frames++;
+                    if (frames <= 8) {
+                        long checksum = 0;
+                        for (byte b : frame.yPlane()) {
+                            checksum = checksum * 31 + (b & 0xFF);
+                        }
+                        System.out.printf("frame %d: %dx%d pixfmt=%d checksum=%d%n",
+                                frames, frame.width(), frame.height(), frame.pixelFormat(), checksum);
+                    }
+                }
+                System.out.printf("Decoded %d frames from %d video packets (%d total packets)%n",
+                        frames, videoPackets, packets);
+            }
+        }
+        return 0;
+    }
+
     private static String hexPrefix(byte[] data, int max) {
         StringBuilder sb = new StringBuilder();
         for (int i = 0; i < Math.min(data.length, max); i++) {

cli/src/main/java/module-info.java

@@ -1,4 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-module dev.quoije.umd.cli {
-    requires dev.quoije.umd.core;
-}