Monte Screen Recorder突发故障 录制生成空白无法播放视频

问题现象 #

此前一直使用MonteScreenRecorder录制测试执行过程，一周前最后一次成功录制的视频可正常使用，近期突然出现录屏异常：测试运行完成后视频文件正常生成到指定目录，但尝试播放时视频无法加载、无法启动播放，全程显示为空白。

现有实现代码 #

录屏工具类代码 #

public class ScreenRecorderUtil extends ScreenRecorder {

 public static ScreenRecorder screenRecorder;
 public String name;
 public ScreenRecorderUtil(GraphicsConfiguration cfg, Rectangle captureArea, Format fileFormat,
   Format screenFormat, Format mouseFormat, Format audioFormat, File movieFolder, String name)
     throws IOException, AWTException {
  super(cfg, captureArea, fileFormat, screenFormat, mouseFormat, audioFormat, movieFolder);
  this.name = name;
 }

 @Override
 protected File createMovieFile(Format fileFormat) throws IOException {

  if (!movieFolder.exists()) {
   movieFolder.mkdirs();
  } else if (!movieFolder.isDirectory()) {
   throw new IOException("\"" + movieFolder + "\" is not a directory.");
  }
  SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH.mm.ss");
  return new File(movieFolder,
    name + "-" + dateFormat.format(new Date()) + "." + Registry.getInstance().getExtension(fileFormat));
 }

 public static void startRecord(String methodName) throws Exception {
  File file = new File("./reports-recordings/");
  Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
  int width = screenSize.width;
  int height = screenSize.height;

  Rectangle captureSize = new Rectangle(0, 0, width, height);

  GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().
    getDefaultScreenDevice()
    .getDefaultConfiguration();
  screenRecorder = new ScreenRecorderUtil(gc, captureSize,
    new Format(MediaTypeKey, MediaType.FILE, MimeTypeKey, MIME_AVI),
    new Format(MediaTypeKey, MediaType.VIDEO, EncodingKey, ENCODING_AVI_TECHSMITH_SCREEN_CAPTURE,
      CompressorNameKey, ENCODING_AVI_TECHSMITH_SCREEN_CAPTURE, DepthKey, 24, FrameRateKey,
      Rational.valueOf(15), QualityKey, 1.0f, KeyFrameIntervalKey, 15 * 60),
    new Format(MediaTypeKey, MediaType.VIDEO, EncodingKey, "black", FrameRateKey, Rational.valueOf(30)),
    null, file, methodName);
  screenRecorder.start();
 }

 public static void stopRecord() throws Exception {
  screenRecorder.stop();
 }
}

测试基类启停逻辑 #

public abstract class BaseTest extends DriverUtil {

    @BeforeMethod
    protected static void openDriver() throws Exception {
        DriverUtil.openBrowser();
        ScreenRecorderUtil.startRecord("TestRecording");
    }

    @AfterMethod
    protected static void cleanUp() throws Exception {
        DriverUtil.closeBrowser();
        ScreenRecorderUtil.stopRecord();
    }

    protected void LOG(String message) {
        TestListener.getTestSection().info(message);
    }

    protected void IMG(String message) {
        String screenshot = ((TakesScreenshot) UIActions.driver).getScreenshotAs(OutputType.BASE64);
        TestListener.getTestSection().addScreenCaptureFromBase64String(screenshot, message);
    }
}

引入的Maven依赖 #

<dependency>
    <groupId>com.github.stephenc.monte</groupId>
    <artifactId>monte-screen-recorder</artifactId>
    <version>0.7.7.0</version>
</dependency>

故障原因与修复方案 #

按优先级从高到低排查修复：

• 鼠标格式配置错误：当前代码中mouseFormat参数的EncodingKey被设置为"black"，属于非法配置。该参数用于指定鼠标光标的编码格式，传入"black"会触发编码器异常，输出全黑/空白帧，之前可正常使用是因为旧版本JDK或系统组件未对该参数做合法性校验，近期环境更新后参数校验生效触发问题。将该参数替换为合法配置即可：

  new Format(MediaTypeKey, MediaType.VIDEO, EncodingKey, ENCODING_AVI_TECHSMITH_SCREEN_CAPTURE, FrameRateKey, Rational.valueOf(30))
  

• 停止录屏时序错误：当前@AfterMethod逻辑中先关闭浏览器再停止录屏，浏览器关闭时触发的资源释放、屏幕重绘可能打断Monte的视频流写入，导致AVI文件头、帧索引损坏，播放器无法识别有效帧。调整执行顺序，先停止录屏再关闭浏览器：

  @AfterMethod
  protected static void cleanUp() throws Exception {
      ScreenRecorderUtil.stopRecord();
      DriverUtil.closeBrowser();
  }
  

• 高DPI缩放适配问题：如果近期系统更新自动开启了125%/150%等非100%显示缩放，Monte 0.7.7.0版本无法自动识别物理分辨率，通过Toolkit.getDefaultToolkit().getScreenSize()拿到的是缩放后的逻辑分辨率，捕获区域超出物理屏幕范围，采集到的全是空帧。两种修复方式二选一：
  • 给JVM启动参数添加-Dsun.java2d.dpiaware=false禁用DPI感知
  • 手动计算缩放比例，将捕获宽高乘以系统缩放系数，匹配物理屏幕分辨率
• 目录权限问题：检查生成的视频文件大小，如果文件大小仅几KB，说明录屏进程只有文件创建权限、没有帧数据写入权限，给./reports-recordings/目录开放当前用户的完全读写权限即可。

内容的提问来源于stack exchange，提问作者zheb