fix incorrect hls segment handling

src/main/java/com/ddf/vodsystem/services/media/StreamActionsService.java

@@ -11,6 +11,7 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
@@ -31,8 +32,6 @@ public class StreamActionsService {
     private static final Logger logger = LoggerFactory.getLogger(StreamActionsService.class);
     private final CommandRunner commandRunner;
 
-    private static final int HLS_SEGMENT_LENGTH = 3;
-
     public StreamActionsService(CommandRunner commandRunner) {
         this.commandRunner = commandRunner;
     }
@@ -65,21 +64,33 @@ public class StreamActionsService {
             float duration,
             Path outputFile,
             ProgressTracker progressTracker
-    ) {
+    ) throws IOException {
+        if (segments.isEmpty()) {
+            return CompletableFuture.failedFuture(new IllegalArgumentException("Segment list cannot be empty"));
+        }
+
+        Path firstSegment = segments.getFirst();
+        Path trimmedFirst = Files.createTempFile("trimmed-first-", ".ts");
         try {
-            String concatInput = segments.stream()
+            // First segment must be trimmed manually due to keyframe issues with the concat protocol
+            List<String> trimCommand = List.of(
+                    "ffmpeg", "-y",
+                    "-ss", String.valueOf(trimOffset),
+                    "-i", firstSegment.toAbsolutePath().toString(),
+                    "-c", "copy",
+                    trimmedFirst.toAbsolutePath().toString()
+            );
+            commandRunner.run(trimCommand);
+
+            String concatInput = Stream.concat(Stream.of(trimmedFirst), segments.stream().skip(1))
                     .map(p -> p.toAbsolutePath().toString())
                     .collect(Collectors.joining("|"));
 
-            if (concatInput.isEmpty()) {
-                throw new IllegalStateException("Must have at least one segment");
-            }
-
             List<String> command = List.of(
                     "ffmpeg",
                     "-y",
-                    "-i", "concat:" + concatInput,
                     "-ss", String.valueOf(trimOffset),
+                    "-i", "concat:" + concatInput,
                     "-t", String.valueOf(duration),
                     "-c", "copy",
                     outputFile.toAbsolutePath().toString()
@@ -101,6 +112,8 @@ public class StreamActionsService {
         } catch (RuntimeException e) {
             logger.error("Failed to save section to '{}': {}", outputFile, e.toString());
             return CompletableFuture.failedFuture(e);
+        } finally {
+            Files.deleteIfExists(trimmedFirst);
         }
     }
 
@@ -112,17 +125,29 @@ public class StreamActionsService {
             throw new IllegalArgumentException("Start time must be before end time");
         }
 
+        List<Path> results = new ArrayList<>();
+
         try (Stream<Path> files = Files.list(streamDirectory)) {
-            return files
+            List<Path> streamFiles = files
                     .filter(p -> p.getFileName().toString().endsWith(".ts"))
                     .filter(Files::isRegularFile)
-                    .filter(p -> {
-                        long segMs = parseTimestampMs(p);
-                        return segMs < endMs && (segMs + HLS_SEGMENT_LENGTH * 1000) > startMs;
-                    })
                     .sorted(Comparator.comparingLong(this::parseTimestampMs))
-                    .collect(Collectors.toList());
+                    .toList();
+
+            for (int i = 0; i < streamFiles.size(); i++) {
+                Path streamFile = streamFiles.get(i);
+                long segmentStart = parseTimestampMs(streamFile);
+                long segmentEnd = (i + 1 < streamFiles.size())
+                        ? parseTimestampMs(streamFiles.get(i + 1))
+                        : Long.MAX_VALUE;
+
+                if (segmentStart < endMs && segmentEnd > startMs) {
+                    results.add(streamFile);
+                }
+            }
         }
+
+        return results;
     }
 
     public long parseTimestampMs(Path path) {