From dd7266a54f1b76ab2368fc436ed533bbb4cb030a Mon Sep 17 00:00:00 2001
From: genteure <genteure@gmail.com>
Date: Mon, 2 May 2022 00:01:41 +0800
Subject: [PATCH] FLV: Small adjustments

---
 .editorconfig                                 |  2 ++
 .../Rules/HandleDelayedAudioHeaderRule.cs     |  5 +---
 .../Pipeline/Rules/HandleEndTagRule.cs        |  2 +-
 .../Pipeline/Rules/HandleNewHeaderRule.cs     |  8 +-----
 .../Pipeline/Rules/HandleNewScriptRule.cs     |  5 +---
 .../Rules/RemoveDuplicatedChunkRule.cs        |  8 ++----
 .../Pipeline/Rules/RemoveFillerDataRule.cs    |  8 +-----
 .../Pipeline/Rules/UpdateTimestampJumpRule.cs | 25 +++++++++++++++----
 .../Rules/UpdateTimestampOffsetRule.cs        | 24 +++++++++++-------
 9 files changed, 44 insertions(+), 43 deletions(-)

diff --git a/.editorconfig b/.editorconfig
index d1193ae..cb0017e 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -127,6 +127,8 @@ csharp_style_var_elsewhere = true:suggestion
 csharp_style_var_for_built_in_types = true:suggestion
 #prefer var when the type is already mentioned on the right-hand side of a declaration expression
 csharp_style_var_when_type_is_apparent = true:suggestion
+# IDE0090: Use 'new(...)'
+csharp_style_implicit_object_creation_when_type_is_apparent = false:suggestion
 
 #Style - language keyword and framework type options
 
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/HandleDelayedAudioHeaderRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/HandleDelayedAudioHeaderRule.cs
index 6a32588..80844ef 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/HandleDelayedAudioHeaderRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/HandleDelayedAudioHeaderRule.cs
@@ -7,11 +7,8 @@ using StructLinq;
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
     /// <summary>
-    /// 处理延后收到的音频头
+    /// 处理延后收到的音频头，移动到音视频数据的前面。
     /// </summary>
-    /// <remarks>
-    /// 本规则应该放在所有规则前面
-    /// </remarks>
     public class HandleDelayedAudioHeaderRule : ISimpleProcessingRule
     {
         private static readonly ProcessingComment comment1 = new ProcessingComment(CommentType.Unrepairable, "音频数据出现在音频头之前");
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/HandleEndTagRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/HandleEndTagRule.cs
index 66e1d85..81ce55f 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/HandleEndTagRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/HandleEndTagRule.cs
@@ -5,7 +5,7 @@ using BililiveRecorder.Flv.Pipeline.Actions;
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
     /// <summary>
-    /// 处理 end tag
+    /// 处理 End Tag，遇到的时候对文件进行分段
     /// </summary>
     public class HandleEndTagRule : ISimpleProcessingRule
     {
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/HandleNewHeaderRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/HandleNewHeaderRule.cs
index a59d14e..2d3575d 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/HandleNewHeaderRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/HandleNewHeaderRule.cs
@@ -8,14 +8,8 @@ using StructLinq.Where;
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
     /// <summary>
-    /// 处理收到音视频 Header 的情况
+    /// 处理音视频 Header。收到音视频 Header 时检查与上一组是否相同，并根据情况删除重复的 Header 或新建文件。<br/>
     /// </summary>
-    /// <remarks>
-    /// 当收到音视频 Header 时检查与上一组是否相同<br/>
-    /// 并根据情况删除重复的 Header 或新建文件写入<br/>
-    /// <br/>
-    /// 本规则为一般规则
-    /// </remarks>
     public class HandleNewHeaderRule : ISimpleProcessingRule
     {
         private const string VIDEO_HEADER_KEY = "HandleNewHeaderRule_VideoHeader";
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/HandleNewScriptRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/HandleNewScriptRule.cs
index 819e2f7..4691a6d 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/HandleNewScriptRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/HandleNewScriptRule.cs
@@ -6,11 +6,8 @@ using BililiveRecorder.Flv.Pipeline.Actions;
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
     /// <summary>
-    /// 处理收到 Script Tag 的情况
+    /// 处理 Script Tag
     /// </summary>
-    /// <remarks>
-    /// 本规则为一般规则
-    /// </remarks>
     public class HandleNewScriptRule : ISimpleProcessingRule
     {
         private const string onMetaData = "onMetaData";
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/RemoveDuplicatedChunkRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/RemoveDuplicatedChunkRule.cs
index 8c357a5..476b553 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/RemoveDuplicatedChunkRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/RemoveDuplicatedChunkRule.cs
@@ -8,13 +8,8 @@ using StructLinq;
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
     /// <summary>
-    /// 删除重复的直播数据
+    /// 删除重复的直播数据。
     /// </summary>
-    /// <remarks>
-    /// 通过对比直播数据的特征，删除重复的直播数据<br/>
-    /// <br/>
-    /// 本规则为一般规则
-    /// </remarks>
     public class RemoveDuplicatedChunkRule : ISimpleProcessingRule
     {
         private const int MAX_HISTORY = 8;
@@ -39,6 +34,7 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
 
                 unchecked
                 {
+                    // TODO: 改成用 Hash 判断
                     // 计算一个特征码
                     // 此处并没有遵循什么特定的算法，只是随便取了一些代表性比较强的值，用简单又尽量可靠的方式糅合到一起而已
                     foreach (var tag in data.Tags)
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/RemoveFillerDataRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/RemoveFillerDataRule.cs
index 77cd83f..ebc9496 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/RemoveFillerDataRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/RemoveFillerDataRule.cs
@@ -4,14 +4,8 @@ using BililiveRecorder.Flv.Pipeline.Actions;
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
     /// <summary>
-    /// 删除 H.264 Filler Data
+    /// 删除 H.264 Filler Data，节省硬盘空间。
     /// </summary>
-    /// <remarks>
-    /// 部分直播码率瞎填的主播的直播数据中存在大量无用的 Filler Data<br/>
-    /// 录制这些主播时删除这些数据可以节省硬盘空间<br/>
-    /// <br/>
-    /// 本规则应该放在一般规则前面
-    /// </remarks>
     public class RemoveFillerDataRule : ISimpleProcessingRule
     {
         public void Run(FlvProcessingContext context, Action next)
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampJumpRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampJumpRule.cs
index 9ed3299..17913b7 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampJumpRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampJumpRule.cs
@@ -7,6 +7,9 @@ using StructLinq;
 
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
+    /// <summary>
+    /// 修复时间戳跳变
+    /// </summary>
     public class UpdateTimestampJumpRule : ISimpleProcessingRule
     {
         private const string TS_STORE_KEY = "Timestamp_Store_Key";
@@ -25,12 +28,14 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
         {
             next();
 
+            // 之前直播流的时间戳信息保存在 SessionItems 里
             var ts = context.SessionItems.ContainsKey(TS_STORE_KEY) ? context.SessionItems[TS_STORE_KEY] as TimestampStore ?? new TimestampStore() : new TimestampStore();
             context.SessionItems[TS_STORE_KEY] = ts;
 
+            // 按顺序处理每个 Action
             foreach (var action in context.Actions)
             {
-                if (action is PipelineDataAction dataAction)
+                if (action is PipelineDataAction dataAction) // 如果是直播数据，计算并调整时间戳
                 {   // SetDataTimestamp
                     var tags = dataAction.Tags;
                     var currentTimestamp = tags[0].Timestamp;
@@ -53,7 +58,7 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
 
                     ts.NextTimestampTarget = this.CalculateNewTarget(tags);
                 }
-                else if (action is PipelineEndAction endAction)
+                else if (action is PipelineEndAction endAction) // End Tag 其实怎么处理都无所谓
                 {
                     var tag = endAction.Tag;
                     var diff = tag.Timestamp - ts.LastOriginal;
@@ -66,16 +71,16 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
                         tag.Timestamp -= ts.CurrentOffset;
                     }
                 }
-                else if (action is PipelineNewFileAction)
+                else if (action is PipelineNewFileAction) // 如果新建文件分段了，重设时间戳信息重新从 0 开始
                 {
                     ts.Reset();
                 }
-                else if (action is PipelineScriptAction s)
+                else if (action is PipelineScriptAction s) // Script Tag 时间戳永远为 0
                 {
                     s.Tag.Timestamp = 0;
                     ts.Reset();
                 }
-                else if (action is PipelineHeaderAction h)
+                else if (action is PipelineHeaderAction h) // Header Tag 时间戳永远为 0
                 {
                     if (h.VideoHeader != null)
                         h.VideoHeader.Timestamp = 0;
@@ -86,6 +91,7 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
             }
         }
 
+        // 计算理想情况下这段数据后面下一个 Tag 的时间戳应该是多少
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private int CalculateNewTarget(IReadOnlyList<Tag> tags)
         {
@@ -123,10 +129,19 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
 
         private class TimestampStore
         {
+            /// <summary>
+            /// 下一个 Tag 的目标时间戳
+            /// </summary>
             public int NextTimestampTarget;
 
+            /// <summary>
+            /// 上一个 Tag 的原始时间戳
+            /// </summary>
             public int LastOriginal;
 
+            /// <summary>
+            /// 当前时间戳偏移量
+            /// </summary>
             public int CurrentOffset;
 
             public void Reset()
diff --git a/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampOffsetRule.cs b/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampOffsetRule.cs
index 82e7ed6..d98636c 100644
--- a/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampOffsetRule.cs
+++ b/BililiveRecorder.Flv/Pipeline/Rules/UpdateTimestampOffsetRule.cs
@@ -7,10 +7,13 @@ using StructLinq;
 
 namespace BililiveRecorder.Flv.Pipeline.Rules
 {
+    /// <summary>
+    /// 修复时间戳错位
+    /// </summary>
     public class UpdateTimestampOffsetRule : ISimpleProcessingRule
     {
-        private static readonly ProcessingComment comment1 = new ProcessingComment(CommentType.Unrepairable, "GOP 内音频或视频时间戳不连续");
-        private static readonly ProcessingComment comment2 = new ProcessingComment(CommentType.Unrepairable, "出现了无法计算偏移量的音视频偏移");
+        private static readonly ProcessingComment COMMENT_JumpedWithinGOP = new ProcessingComment(CommentType.Unrepairable, "GOP 内音频或视频时间戳不连续");
+        private static readonly ProcessingComment COMMENT_CantSolve = new ProcessingComment(CommentType.Unrepairable, "出现了无法计算偏移量的音视频偏移");
 
         public void Run(FlvProcessingContext context, Action next)
         {
@@ -18,9 +21,12 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
             next();
         }
 
-        private readonly struct IsNotNormal : ITwoInputFunction<Tag, bool>
+        /// <summary>
+        /// 检查 Tag 时间戳是否有变小的情况
+        /// </summary>
+        private readonly struct IsNextTimestampSmaller : ITwoInputFunction<Tag, bool>
         {
-            public static IsNotNormal Instance;
+            public static IsNextTimestampSmaller Instance;
             public bool Eval(Tag a, Tag b) => a.Timestamp > b.Timestamp;
         }
 
@@ -28,19 +34,19 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
         {
             if (action is PipelineDataAction data)
             {
-                var isNotNormal = data.Tags.Any2(ref IsNotNormal.Instance);
+                var isNotNormal = data.Tags.Any2(ref IsNextTimestampSmaller.Instance);
                 if (!isNotNormal)
                 {
-                    // 没有问题
+                    // 没有问题，每个 tag 的时间戳都 >= 上一个 tag 的时间戳。
                     yield return data;
                     yield break;
                 }
 
-                if (data.Tags.Where(x => x.Type == TagType.Audio).Any2(ref IsNotNormal.Instance) || data.Tags.Where(x => x.Type == TagType.Video).Any2(ref IsNotNormal.Instance))
+                if (data.Tags.Where(x => x.Type == TagType.Audio).Any2(ref IsNextTimestampSmaller.Instance) || data.Tags.Where(x => x.Type == TagType.Video).Any2(ref IsNextTimestampSmaller.Instance))
                 {
                     // 音频或视频自身就有问题，没救了
                     yield return PipelineDisconnectAction.Instance;
-                    context.AddComment(comment1);
+                    context.AddComment(COMMENT_JumpedWithinGOP);
                     yield break;
                 }
                 else
@@ -150,7 +156,7 @@ namespace BililiveRecorder.Flv.Pipeline.Rules
                     yield break;
 
                 invalidOffset:
-                    context.AddComment(comment2);
+                    context.AddComment(COMMENT_CantSolve);
                     yield return PipelineDisconnectAction.Instance;
                     yield break;
                 }