Add "Maximum video bitrate" option

src/utils/sdp.ts

@@ -0,0 +1,61 @@
+export function patchSdpBitrate(sdp: string, video?: number, audio?: number) {
+    const lines = sdp.split('\n');
+
+    const mediaSet: Set<string> = new Set();
+    !!video && mediaSet.add('video');
+    !!audio && mediaSet.add('audio');
+
+    const bitrate = {
+        video,
+        audio,
+    };
+
+    for (let lineNumber = 0; lineNumber < lines.length; lineNumber++) {
+        let media: string = '';
+
+        let line = lines[lineNumber];
+        if (!line.startsWith('m=')) {
+            continue;
+        }
+
+        for (const m of mediaSet) {
+            if (line.startsWith(`m=${m}`)) {
+                media = m;
+                // Remove matched media from set
+                mediaSet.delete(media);
+                break;
+            }
+        }
+
+        // Invalid media, continue looking
+        if (!media) {
+            continue;
+        }
+
+        const bLine = `b=AS:${bitrate[media as keyof typeof bitrate]}`;
+
+        while (lineNumber++, lineNumber < lines.length) {
+            line = lines[lineNumber];
+            // Ignore lines that start with "i=" or "c="
+            if (line.startsWith('i=') || line.startsWith('c=')) {
+                continue;
+            }
+
+            if (line.startsWith('b=AS:')) {
+                // Replace bitrate
+                lines[lineNumber] = bLine;
+                // Stop lookine for "b=AS:" line
+                break;
+            }
+
+            if (line.startsWith('m=')) {
+                // "b=AS:" line not found, add "b" line before "m="
+                lines.splice(lineNumber, 0, bLine);
+                // Stop
+                break;
+            }
+        }
+    }
+
+    return lines.join('\n');
+}