Fix EXT-X-MAP

superstreamerapp · Dec 13, 2024 · c66809b · c66809b
1 parent 483a7cc
commit c66809b
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Showing 2 changed files with 28 additions and 12 deletions.
diff --git a/packages/stitcher/src/parser/parse.ts b/packages/stitcher/src/parser/parse.ts
@@ -88,7 +88,12 @@ function formatMediaPlaylist(tags: Tag[]): MediaPlaylist {
   const segments: Segment[] = [];
   let segmentStart = -1;
 
-  tags.forEach(([name], index) => {
+  let map: MediaInitializationSection | undefined;
+  tags.forEach(([name, value], index) => {
+    if (name === "EXT-X-MAP") {
+      map = value;
+    }
+
     if (isSegmentTag(name)) {
       segmentStart = index - 1;
     }
@@ -100,7 +105,7 @@ function formatMediaPlaylist(tags: Tag[]): MediaPlaylist {
       const segmentTags = tags.slice(segmentStart, index + 1);
       const uri = nextLiteral(segmentTags, segmentTags.length - 2);
 
-      const segment = parseSegment(segmentTags, uri);
+      const segment = parseSegment(segmentTags, uri, map);
       segments.push(segment);
 
       segmentStart = -1;
@@ -140,18 +145,20 @@ function isSegmentTag(name: Tag[0]) {
   switch (name) {
     case "EXTINF":
     case "EXT-X-DISCONTINUITY":
-    case "EXT-X-MAP":
     case "EXT-X-PROGRAM-DATE-TIME":
       return true;
   }
   return false;
 }
 
-function parseSegment(tags: Tag[], uri: string): Segment {
+function parseSegment(
+  tags: Tag[],
+  uri: string,
+  map?: MediaInitializationSection,
+): Segment {
   let duration: number | undefined;
   let discontinuity: boolean | undefined;
   let programDateTime: DateTime | undefined;
-  let map: MediaInitializationSection | undefined;
 
   tags.forEach(([name, value]) => {
     if (name === "EXTINF") {
@@ -163,9 +170,6 @@ function parseSegment(tags: Tag[], uri: string): Segment {
     if (name === "EXT-X-PROGRAM-DATE-TIME") {
       programDateTime = value;
     }
-    if (name === "EXT-X-MAP") {
-      map = value;
-    }
   });
 
   assert(duration, "parseSegment: duration not found");

diff --git a/packages/stitcher/src/parser/stringify.ts b/packages/stitcher/src/parser/stringify.ts
@@ -1,4 +1,8 @@
-import type { MasterPlaylist, MediaPlaylist } from "./types";
+import type {
+  MasterPlaylist,
+  MediaInitializationSection,
+  MediaPlaylist,
+} from "./types";
 
 export function stringifyMasterPlaylist(playlist: MasterPlaylist) {
   const lines: string[] = [];
@@ -94,10 +98,18 @@ export function stringifyMediaPlaylist(playlist: MediaPlaylist) {
     lines.push(`#EXT-X-PLAYLIST-TYPE:${playlist.playlistType}`);
   }
 
+  let lastMap: MediaInitializationSection | undefined;
+
   playlist.segments.forEach((segment) => {
-    if (segment.map) {
-      const attrs = [`URI="${segment.map.uri}"`];
-      lines.push(`#EXT-X-MAP:${attrs.join(",")}`);
+    // See https://datatracker.ietf.org/doc/html/draft-pantos-hls-rfc8216bis-16#section-4.4.4.5
+    // It applies to every Media Segment that appears after it in the Playlist until the next
+    // EXT-X-MAP tag or until the end of the Playlist.
+    if (segment.map !== lastMap) {
+      if (segment.map) {
+        const attrs = [`URI="${segment.map.uri}"`];
+        lines.push(`#EXT-X-MAP:${attrs.join(",")}`);
+      }
+      lastMap = segment.map;
     }
 
     if (segment.discontinuity) {