diff --git a/BililiveRecorder.Flv/Amf/ScriptTagBodyExtensions.cs b/BililiveRecorder.Flv/Amf/ScriptTagBodyExtensions.cs
index ca64aed..b9bc341 100644
--- a/BililiveRecorder.Flv/Amf/ScriptTagBodyExtensions.cs
+++ b/BililiveRecorder.Flv/Amf/ScriptTagBodyExtensions.cs
@@ -2,6 +2,18 @@ namespace BililiveRecorder.Flv.Amf
 {
     public static class ScriptTagBodyExtensions
     {
-        public static ScriptDataEcmaArray? GetMetadataValue(this ScriptTagBody body) => body.Values.Count > 1 ? body.Values[1] as ScriptDataEcmaArray : null;
+        public static ScriptDataEcmaArray? GetMetadataValue(this ScriptTagBody body)
+        {
+            if (body.Values.Count > 1)
+            {
+                return body.Values[1] switch
+                {
+                    ScriptDataEcmaArray array => array,
+                    ScriptDataObject oect => oect,
+                    _ => null
+                };
+            }
+            else return null;
+        }
     }
 }
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/FfmpegDetectionRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/FfmpegDetectionRule.cs
index 2179ecd..d047ee6 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/FfmpegDetectionRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/FfmpegDetectionRule.cs
@@ -18,7 +18,7 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
             if (!this.LavfEncoderDetected && context.Actions.Any(action =>
             {
                 if (action is PipelineScriptAction scriptAction
-                    && (scriptAction?.Tag?.ScriptData?.GetMetadataValue()?.Value?.TryGetValue("encoder", out var encoderValue) ?? false)
+                    && (scriptAction?.Tag?.ScriptData?.GetMetadataValue()?.TryGetValue("encoder", out var encoderValue) ?? false)
                     && encoderValue is ScriptDataString encoder)
                     return encoder.Value.StartsWith("Lavf", StringComparison.Ordinal);
                 return false;
diff --git a/test/BililiveRecorder.Flv.Tests/RuleTests/FfmpegDetectionRuleTests.cs b/test/BililiveRecorder.Flv.Tests/RuleTests/FfmpegDetectionRuleTests.cs
new file mode 100644
index 0000000..6bd6c57
--- /dev/null
+++ b/test/BililiveRecorder.Flv.Tests/RuleTests/FfmpegDetectionRuleTests.cs
@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using BililiveRecorder.Flv.Amf;
+using BililiveRecorder.Flv.Pipeline;
+using BililiveRecorder.Flv.Pipeline.Actions;
+using BililiveRecorder.Flv.Pipeline.Rules;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+
+namespace BililiveRecorder.Flv.Tests.RuleTests
+{
+    public class FfmpegDetectionRuleTests
+    {
+        [Theory]
+        [MemberData(nameof(EndTagTestData))]
+        public void ShouldDetectEndTag(bool expectEndTag, PipelineAction pipelineAction)
+        {
+            var rule = new FfmpegDetectionRule();
+            var pipeline = new ProcessingPipelineBuilder(new ServiceCollection().BuildServiceProvider()).Add(rule).Build();
+
+            var context = new FlvProcessingContext(pipelineAction, new Dictionary<object, object?>());
+
+            pipeline(context);
+
+            Assert.Equal(expectEndTag, rule.EndTagDetected);
+        }
+
+        private static IEnumerable<object[]> EndTagTestData()
+        {
+            yield return new object[] { true, new PipelineEndAction(new Tag()) };
+            yield return new object[] { false, new PipelineScriptAction(new Tag()) };
+            yield return new object[] { false, new PipelineHeaderAction(Array.Empty<Tag>()) };
+            yield return new object[] { false, new PipelineDataAction(Array.Empty<Tag>()) };
+            yield return new object[] { false, PipelineNewFileAction.Instance };
+        }
+
+        [Theory]
+        [InlineData(true, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""Object"",""Value"":{""encoder"":{""Type"":""String"",""Value"":""Lavf56.40.101""}}}]")]
+        [InlineData(true, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""EcmaArray"",""Value"":{""encoder"":{""Type"":""String"",""Value"":""Lavf56.40.101""}}}]")]
+        [InlineData(true, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""Object"",""Value"":{""encoder"":{""Type"":""String"",""Value"":""Lavf56.40.101""}}},{""Type"":""Null""}]")]
+        [InlineData(true, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""Object"",""Value"":{""encoder"":{""Type"":""String"",""Value"":""Lavf123""}}}]")]
+        [InlineData(false, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""EcmaArray"",""Value"":{""encoder"":{""Type"":""String"",""Value"":""libobs xxxx""}}}]")]
+        [InlineData(false, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""EcmaArray"",""Value"":{}}]")]
+        [InlineData(false, @"[{""Type"":""String"",""Value"":""onMetaData""},{""Type"":""Object"",""Value"":{}}]")]
+        [InlineData(false, @"[{""Type"":""String"",""Value"":""aaa""},{""Type"":""Object"",""Value"":{}}]")]
+        public void ShouldDetectLvafEncoder(bool expectedValue, string metadataJson)
+        {
+            var rule = new FfmpegDetectionRule();
+            var pipeline = new ProcessingPipelineBuilder(new ServiceCollection().BuildServiceProvider()).Add(rule).Build();
+
+            var action = new PipelineScriptAction(new Tag
+            {
+                Type = TagType.Script,
+                ScriptData = ScriptTagBody.Parse(metadataJson)
+            });
+
+            var context = new FlvProcessingContext(action, new Dictionary<object, object?>());
+
+            pipeline(context);
+
+            Assert.Equal(expectedValue, rule.LavfEncoderDetected);
+        }
+    }
+}