fix: Improve audio channel detection for WebRTC (#2280)

- Related: #2191

src/utils/audio.ts

@@ -16,5 +16,9 @@ export const mayHaveAudio = (video: HTMLVideoElement & AudioProperties): boolean
   if (video.audioTracks !== undefined) {
     return Boolean(video.audioTracks?.length);
   }
+  // Check MediaStream audio tracks (reliable for WebRTC at load time)
+  if (typeof MediaStream !== 'undefined' && video.srcObject instanceof MediaStream) {
+    return video.srcObject.getAudioTracks().length > 0;
+  }
   return true;
 };

tests/utils/audio.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
 import { AudioProperties, mayHaveAudio } from '../../src/utils/audio';
 
 // @vitest-environment jsdom
@@ -29,6 +29,36 @@ describe('mayHaveAudio', () => {
     expect(mayHaveAudio(element)).toBeFalsy();
   });
 
+  it('should detect audio when srcObject MediaStream has audio tracks', () => {
+    // Mock MediaStream for jsdom environment
+    const MockMediaStream = class MediaStream {};
+    vi.stubGlobal('MediaStream', MockMediaStream);
+
+    const element = {} as HTMLVideoElement & AudioProperties;
+    const mockStream = new MockMediaStream();
+    (mockStream as unknown as { getAudioTracks: () => unknown[] }).getAudioTracks =
+      () => [{}];
+    element.srcObject = mockStream as unknown as MediaStream;
+    expect(mayHaveAudio(element)).toBeTruthy();
+
+    vi.unstubAllGlobals();
+  });
+
+  it('should not detect audio when srcObject MediaStream has no audio tracks', () => {
+    // Mock MediaStream for jsdom environment
+    const MockMediaStream = class MediaStream {};
+    vi.stubGlobal('MediaStream', MockMediaStream);
+
+    const element = {} as HTMLVideoElement & AudioProperties;
+    const mockStream = new MockMediaStream();
+    (mockStream as unknown as { getAudioTracks: () => unknown[] }).getAudioTracks =
+      () => [];
+    element.srcObject = mockStream as unknown as MediaStream;
+    expect(mayHaveAudio(element)).toBeFalsy();
+
+    vi.unstubAllGlobals();
+  });
+
   it('should detect audio when no evidence to the contrary', () => {
     const element = {} as HTMLVideoElement & AudioProperties;
     expect(mayHaveAudio(element)).toBeTruthy();