fix(jellyfin): keep selecting subtitles when a track download fails (#272)

src/core/services/jellyfin.test.ts

@@ -377,6 +377,14 @@ test('listSubtitleTracks returns all subtitle streams with delivery urls', async
                 DeliveryUrl: 'https://cdn.example.com/subs.srt',
                 IsExternalUrl: true,
               },
+              {
+                Type: 'Subtitle',
+                Index: 5,
+                Codec: 'PGSSUB',
+                Language: 'eng',
+                DisplayTitle: 'English PGS',
+                DeliveryMethod: 'Embed',
+              },
             ],
           },
         ],
@@ -395,10 +403,10 @@ test('listSubtitleTracks returns all subtitle streams with delivery urls', async
       clientInfo,
       'movie-1',
     );
-    assert.equal(tracks.length, 3);
+    assert.equal(tracks.length, 4);
     assert.deepEqual(
       tracks.map((track) => track.index),
-      [2, 3, 4],
+      [2, 3, 4, 5],
     );
     assert.equal(
       tracks[0]!.deliveryUrl,
@@ -409,6 +417,7 @@ test('listSubtitleTracks returns all subtitle streams with delivery urls', async
       'http://jellyfin.local/Videos/movie-1/ms-1/Subtitles/3/Stream.srt?ApiKey=token',
     );
     assert.equal(tracks[2]!.deliveryUrl, 'https://cdn.example.com/subs.srt');
+    assert.equal(tracks[3]!.deliveryUrl, null, 'bitmap subtitles cannot be fetched as text');
   } finally {
     globalThis.fetch = originalFetch;
   }

src/core/services/jellyfin.ts

@@ -146,6 +146,17 @@ function setApiKeyParam(url: URL, accessToken: string): void {
   url.searchParams.set('ApiKey', accessToken);
 }
 
+const IMAGE_SUBTITLE_CODECS = new Set([
+  'pgssub',
+  'pgs',
+  'hdmv_pgs_subtitle',
+  'dvdsub',
+  'dvd_subtitle',
+  'dvbsub',
+  'dvb_subtitle',
+  'xsub',
+]);
+
 function resolveDeliveryUrl(
   session: JellyfinAuthSession,
   stream: JellyfinMediaStream,
@@ -163,6 +174,8 @@ function resolveDeliveryUrl(
   const streamIndex = asIntegerOrNull(stream.Index);
   if (streamIndex === null || !itemId || !mediaSourceId) return null;
   const codec = ensureString(stream.Codec).toLowerCase();
+  // Jellyfin cannot convert bitmap subtitles to text, so requesting them always fails.
+  if (IMAGE_SUBTITLE_CODECS.has(codec)) return null;
   const ext =
     codec === 'subrip'
       ? 'srt'