[feat] package rtprtcp: 增加RTPPackerAVC，用于将h264 Nalu包切割成RTP包

pkg/rtprtcp/rtp_packer_avc.go

@@ -0,0 +1,87 @@
+// Copyright 2021, Chef.  All rights reserved.
+// https://github.com/q191201771/lal
+//
+// Use of this source code is governed by a MIT-style license
+// that can be found in the License file.
+//
+// Author: Chef (191201771@qq.com)
+
+package rtprtcp
+
+import "github.com/q191201771/lal/pkg/avc"
+
+const (
+	fuaHeaderSize = 2
+)
+
+type RTPPackerAVC struct {
+}
+
+// @param nalu: AVCC格式
+//
+// @return 返回RTP(only body)的数组
+//         内存块为独立申请，函数返回后，内部不再持有该内存块
+//
+func (*RTPPackerAVC) Pack(nalu []byte, maxSize int) (ret [][]byte) {
+	if nalu == nil || maxSize <= 0 {
+		return
+	}
+
+	nals, err := avc.IterateNALUAVCC(nalu)
+	if err != nil {
+		return
+	}
+
+	for _, nal := range nals {
+		nalType := nal[0] & 0x1F
+		nri := nal[0] & 0x60
+
+		if nalType == avc.NALUTypeAUD {
+			continue
+		}
+
+		// single
+		if len(nal) <= maxSize-fuaHeaderSize {
+			item := make([]byte, len(nal))
+			copy(item, nal)
+			ret = append(ret, item)
+			continue
+		}
+
+		// FU-A
+		var length int
+		bpos := 0
+		epos := len(nal)
+		for {
+			if epos-bpos > maxSize-fuaHeaderSize {
+				// 前面的包
+				length = maxSize
+				item := make([]byte, maxSize)
+				// fuIndicator
+				item[0] = NALUTypeAVCFUA
+				item[0] |= nri
+				// fuHeader
+				item[1] = nalType
+				if bpos == 0 {
+					item[1] |= 0x80 // start
+				}
+				//
+				copy(item[fuaHeaderSize:], nal[bpos:bpos+maxSize-fuaHeaderSize])
+				bpos += maxSize - fuaHeaderSize
+				continue
+			}
+
+			// 最后一包
+			length = epos - bpos + fuaHeaderSize
+			item := make([]byte, length)
+			// fuIndicator
+			item[0] = NALUTypeAVCFUA
+			item[0] |= nri
+			// fuHeader
+			item[1] = nalType | 0x40 // end
+			copy(item[fuaHeaderSize:], nal[bpos:])
+			break
+		}
+	}
+	return
+}