diff --git a/src/Extension/Frame.cpp b/src/Extension/Frame.cpp
index 2b25ea19..e7066bb3 100644
--- a/src/Extension/Frame.cpp
+++ b/src/Extension/Frame.cpp
@@ -180,6 +180,7 @@ bool FrameMerger::willFlush(const Frame::Ptr &frame) const{
                 }
                 default: break;
             }
+            //遇到新帧、或时间戳变化或缓存太多，防止内存溢出，则flush输出
             return new_frame || _frameCached.back()->dts() != frame->dts() || _frameCached.size() > kMaxFrameCacheSize;
         }
 
@@ -192,30 +193,20 @@ bool FrameMerger::willFlush(const Frame::Ptr &frame) const{
             switch (frame->getCodecId()) {
                 case CodecH264 : {
                     auto type = H264_TYPE(frame->data()[frame->prefixSize()]);
-                    if ((frame->data()[frame->prefixSize() + 1] & 0x80) != 0 && type >= H264Frame::NAL_B_P &&
-                        type <= H264Frame::NAL_IDR) {// sei aud pps sps 不判断
-                        //264 新一帧的开始，刷新输出
-                        return true;
-                    } else {
-                        // 不刷新输出
-                        return false;
-                    }
-                    break;
+                    // sei aud pps sps 不判断；264 新一帧的开始，刷新输出
+                    return (frame->data()[frame->prefixSize() + 1] & 0x80) != 0 && type >= H264Frame::NAL_B_P &&
+                           type <= H264Frame::NAL_IDR;
                 }
                 case CodecH265 : {
                     auto type = H265_TYPE(frame->data()[frame->prefixSize()]);
-                    if ((type >= H265Frame::NAL_TRAIL_R && type <= H265Frame::NAL_RSV_IRAP_VCL23) &&
-                        ((frame->data()[frame->prefixSize() + 2] >> 7 & 0x01) != 0)) {
-                        //first_slice_segment_in_pic_flag is frame start  
-                        return true;
-                    } else {
-                        return false;
-                    }
-                    break;
+                    //first_slice_segment_in_pic_flag is frame start
+                    return (type >= H265Frame::NAL_TRAIL_R && type <= H265Frame::NAL_RSV_IRAP_VCL23) &&
+                           ((frame->data()[frame->prefixSize() + 2] >> 7 & 0x01) != 0);
                 }
-                default : break;
+                default :
+                    //缓存太多，防止内存溢出
+                    return _frameCached.size() > kMaxFrameCacheSize;
             }
-            return _frameCached.size() > kMaxFrameCacheSize;
         }
         default: /*不可达*/ assert(0); return true;
     }
@@ -224,10 +215,16 @@ bool FrameMerger::willFlush(const Frame::Ptr &frame) const{
 void FrameMerger::doMerge(BufferLikeString &merged, const Frame::Ptr &frame) const{
     switch (_type) {
         case none : {
+            //此处是合并ps解析输出的流，解析出的流可能是半帧或多帧，不能简单的根据nal type过滤
+            //此流程只用于合并ps解析输出为H264/H265，后面流程有split和忽略无效帧操作
             merged.append(frame->data(), frame->size());
             break;
         }
         case h264_prefix: {
+            if (shouldDrop(frame)) {
+                //h264头模式过滤无效的帧
+                break;
+            }
             if (frame->prefixSize()) {
                 merged.append(frame->data(), frame->size());
             } else {
@@ -237,6 +234,10 @@ void FrameMerger::doMerge(BufferLikeString &merged, const Frame::Ptr &frame) con
             break;
         }
         case mp4_nal_size: {
+            if (shouldDrop(frame)) {
+                //MP4头模式过滤无效的帧
+                break;
+            }
             uint32_t nalu_size = (uint32_t) (frame->size() - frame->prefixSize());
             nalu_size = htonl(nalu_size);
             merged.append((char *) &nalu_size, 4);
@@ -250,26 +251,26 @@ void FrameMerger::doMerge(BufferLikeString &merged, const Frame::Ptr &frame) con
 bool FrameMerger::shouldDrop(const Frame::Ptr &frame) const{
     switch (frame->getCodecId()) {
         case CodecH264: {
-            auto type = H264_TYPE(frame->data()[frame->prefixSize()]);
-            if (type == H264Frame::NAL_SEI || type == H264Frame::NAL_AUD) {
-                // 防止吧AUD或者SEI当成一帧
-                return true;
+            switch (H264_TYPE(frame->data()[frame->prefixSize()])) {
+                // 防止把AUD或者SEI当成一帧
+                case H264Frame::NAL_SEI:
+                case H264Frame::NAL_AUD: return true;
+                default: return false;
             }
-            break;
         }
+
         case CodecH265: {
-            //如果是新的一帧，前面的缓存需要输出
-            auto type = H265_TYPE(frame->data()[frame->prefixSize()]);
-            if (type == H265Frame::NAL_AUD || type == H265Frame::NAL_SEI_PREFIX || type == H265Frame::NAL_SEI_SUFFIX) {
-                // 防止吧AUD或者SEI当成一帧
-                return true;
+            switch (H265_TYPE(frame->data()[frame->prefixSize()])) {
+                // 防止把AUD或者SEI当成一帧
+                case H265Frame::NAL_AUD:
+                case H265Frame::NAL_SEI_SUFFIX:
+                case H265Frame::NAL_SEI_PREFIX: return true;
+                default: return false;
             }
-            break;
         }
-        default:
-            break;
+
+        default: return false;
     }
-    return false;
 }
 
 bool FrameMerger::frameCacheHasVCL(List<Frame::Ptr> &frameCached) const {
@@ -307,9 +308,6 @@ bool FrameMerger::frameCacheHasVCL(List<Frame::Ptr> &frameCached) const {
 }
 
 void FrameMerger::inputFrame(const Frame::Ptr &frame, const onOutput &cb) {
-    if (shouldDrop(frame)) {
-        return;
-    }
     if (willFlush(frame) && frameCacheHasVCL(_frameCached)) {
         Frame::Ptr back = _frameCached.back();
         Buffer::Ptr merged_frame = back;
@@ -325,6 +323,10 @@ void FrameMerger::inputFrame(const Frame::Ptr &frame, const onOutput &cb) {
                     have_idr = true;
                 }
             });
+            if (merged.empty()) {
+                _frameCached.clear();
+                return;
+            }
             merged_frame = std::make_shared<BufferOffset<BufferLikeString> >(std::move(merged));
         }
         cb(back->dts(), back->pts(), merged_frame, have_idr);