snapshot of https://github.com/jitsi/jitsi-meet.git @ fd1749dd28f4138aa80234fc7f311b19aaffa0e7 (2026-09-15)

react/features/base/lastn/functions.ts

@@ -0,0 +1,24 @@
+import { VIDEO_QUALITY_LEVELS } from '../../video-quality/constants';
+
+/**
+ * Determines the lastN value to be used for the conference based on the video quality selected.
+ *
+ * @param {string} qualityLevel - Quality level (height) selected.
+ * @param {number} channelLastN - LastN value set for the whole conference.
+ * @returns {number} LastN value applicable to the quality level specified.
+ */
+export function getLastNForQualityLevel(qualityLevel: number, channelLastN: number) {
+    let lastN = channelLastN;
+
+    const videoQualityLevels = Object.values(VIDEO_QUALITY_LEVELS);
+
+    for (const lvl in videoQualityLevels) {
+        if (videoQualityLevels.hasOwnProperty(lvl)
+            && qualityLevel === videoQualityLevels[lvl]
+            && Number(lvl) > 1) {
+            lastN = Math.floor(channelLastN / Math.pow(2, Number(lvl) - 1));
+        }
+    }
+
+    return lastN;
+}