fix: Handle thumbnails in low-latency chunked mode

Thumbnails cannot be chunked like MP4 segments and were failing in
low-latency streams.

Author: thasso

cmd/livesim2/app/handler_livesim.go

@@ -315,7 +315,7 @@ func writeSegment(ctx context.Context, w http.ResponseWriter, log *slog.Logger,
 			return code, nil
 		}
 	}
-	if cfg.AvailabilityTimeCompleteFlag {
+	if cfg.AvailabilityTimeCompleteFlag || isImage(segmentPart) {
 		return 0, writeLiveSegment(log, w, cfg, drmCfg, vodFS, a, segmentPart, nowMS, tt, isLast)
 	}
 	// Chunked low-latency mode

cmd/livesim2/app/handler_livesim_test.go

@@ -163,6 +163,13 @@ func TestFetches(t *testing.T) {
 			wantedStatusCode:  http.StatusOK,
 			wantedContentType: `image/jpeg`,
 		},
+		{
+			desc:              "thumbnail in low-latency mode",
+			url:               "testpic_2s/thumbs/1.jpg?nowMS=12000",
+			params:            "ato_1/chunkdur_1/",
+			wantedStatusCode:  http.StatusOK,
+			wantedContentType: `image/jpeg`,
+		},
 		{
 			desc:              "imsc1 image subtitle",
 			url:               "testpic_2s/imsc1_img_en/300.m4s?nowMS=610000",