统一帧合并逻辑

2026-06-15 20:45:57 +08:00 · 2021-04-26 18:26:07 +08:00
parent d005ccf396
commit af2b1246fd
12 changed files with 173 additions and 186 deletions
--- a/src/Extension/Frame.cpp
+++ b/src/Extension/Frame.cpp
@@ -140,4 +140,102 @@ const char *CodecInfo::getCodecName() {
 TrackType CodecInfo::getTrackType() {
    return mediakit::getTrackType(getCodecId());
 }
+
+static size_t constexpr kMaxFrameCacheSize = 100;
+
+bool FrameMerger::willFlush(const Frame::Ptr &frame) const{
+    if (_frameCached.empty()) {
+        return false;
+    }
+    switch (_type) {
+        case none : {
+            //frame不是完整的帧，我们合并为一帧
+            bool new_frame = false;
+            switch (frame->getCodecId()) {
+                case CodecH264:
+                case CodecH265: {
+                    //如果是新的一帧，前面的缓存需要输出
+                    new_frame = frame->prefixSize();
+                    break;
+                }
+                default: break;
+            }
+            return new_frame || _frameCached.back()->dts() != frame->dts() || _frameCached.size() > kMaxFrameCacheSize;
+        }
+
+        case mp4_nal_size:
+        case h264_prefix: {
+            if (_frameCached.back()->dts() != frame->dts()) {
+                //时间戳变化了
+                return true;
+            }
+            if (frame->getCodecId() == CodecH264 &&
+                H264_TYPE(frame->data()[frame->prefixSize()]) == H264Frame::NAL_B_P) {
+                //如果是264的b/p帧，那么也刷新输出
+                return true;
+            }
+            return _frameCached.size() > kMaxFrameCacheSize;
+        }
+        default: /*不可达*/ assert(0); return true;
+    }
+}
+
+void FrameMerger::doMerge(BufferLikeString &merged, const Frame::Ptr &frame) const{
+    switch (_type) {
+        case none : {
+            merged.append(frame->data(), frame->size());
+            break;
+        }
+        case h264_prefix: {
+            if (frame->prefixSize()) {
+                merged.append(frame->data(), frame->size());
+            } else {
+                merged.append("\x00\x00\x00\x01", 4);
+                merged.append(frame->data(), frame->size());
+            }
+            break;
+        }
+        case mp4_nal_size: {
+            uint32_t nalu_size = (uint32_t) (frame->size() - frame->prefixSize());
+            nalu_size = htonl(nalu_size);
+            merged.append((char *) &nalu_size, 4);
+            merged.append(frame->data() + frame->prefixSize(), frame->size() - frame->prefixSize());
+            break;
+        }
+        default: /*不可达*/ assert(0); break;
+    }
+}
+
+void FrameMerger::inputFrame(const Frame::Ptr &frame, const onOutput &cb) {
+    if (willFlush(frame)) {
+        Frame::Ptr back = _frameCached.back();
+        Buffer::Ptr merged_frame = back;
+        bool have_idr = back->keyFrame();
+
+        if (_frameCached.size() != 1 || _type == mp4_nal_size) {
+            //在MP4模式下，一帧数据也需要在前添加nalu_size
+            BufferLikeString merged;
+            merged.reserve(back->size() + 1024);
+            _frameCached.for_each([&](const Frame::Ptr &frame) {
+                doMerge(merged, frame);
+                if (frame->keyFrame()) {
+                    have_idr = true;
+                }
+            });
+            merged_frame = std::make_shared<BufferOffset<BufferLikeString> >(std::move(merged));
+        }
+        cb(back->dts(), back->pts(), merged_frame, have_idr);
+        _frameCached.clear();
+    }
+    _frameCached.emplace_back(Frame::getCacheAbleFrame(frame));
+}
+
+FrameMerger::FrameMerger(int type) {
+    _type = type;
+}
+
+void FrameMerger::clear() {
+    _frameCached.clear();
+}
+
 }//namespace mediakit