fix camera startup fallbacks

client/src/pages/LiveCamera.tsx

@@ -17,7 +17,7 @@ import { Slider } from "@/components/ui/slider";
 import { Switch } from "@/components/ui/switch";
 import { formatDateTimeShanghai } from "@/lib/time";
 import { toast } from "sonner";
-import { applyTrackZoom, type CameraQualityPreset, getCameraVideoConstraints, getLiveAnalysisBitrate, readTrackZoomState } from "@/lib/camera";
+import { applyTrackZoom, type CameraQualityPreset, getLiveAnalysisBitrate, readTrackZoomState, requestCameraStream } from "@/lib/camera";
 import {
   ACTION_WINDOW_FRAMES,
   AVATAR_PRESETS,
@@ -1221,20 +1221,24 @@ export default function LiveCamera() {
       if (streamRef.current) {
         streamRef.current.getTracks().forEach((track) => track.stop());
       }
-
-      const constraints: MediaStreamConstraints = {
-        video: getCameraVideoConstraints(nextFacing, mobile, preset),
-        audio: false,
-      };
-
-      const stream = await navigator.mediaDevices.getUserMedia(constraints);
+      const { stream, appliedFacingMode, usedFallback } = await requestCameraStream({
+        facingMode: nextFacing,
+        isMobile: mobile,
+        preset,
+      });
       streamRef.current = stream;
+      if (appliedFacingMode !== nextFacing) {
+        setFacing(appliedFacingMode);
+      }
       if (videoRef.current) {
         videoRef.current.srcObject = stream;
         await videoRef.current.play();
       }
       await syncZoomState(preferredZoom, stream.getVideoTracks()[0] || null);
       setCameraActive(true);
+      if (usedFallback) {
+        toast.info("当前设备已自动切换到兼容摄像头模式");
+      }
       toast.success("摄像头已启动");
     } catch (error: any) {
       toast.error(`摄像头启动失败: ${error?.message || "未知错误"}`);