Inital dump of working code

Author: benjojo

.gitignore

@@ -0,0 +1,2 @@
+de-ip-hdmi
+*.mjpeg

main.go

@@ -0,0 +1,127 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"flag"
+	"fmt"
+	"github.com/miekg/pcap"
+	"io"
+	"log"
+	"os"
+)
+
+type Frame struct {
+	FrameID   uint16
+	LastChunk uint16
+	Data      []byte
+}
+
+func main() {
+	interf := flag.String("interface", "eth0", "What interface the device is attached to")
+	flag.Parse()
+
+	MULTICAST_MAC := []byte{0x01, 0x00, 0x5e, 0x02, 0x02, 0x02}
+
+	h, err := pcap.OpenLive(*interf, 1500, true, 500)
+	if h == nil {
+		fmt.Fprintf(os.Stderr, "de hdmi: %s\n", err)
+		return
+	}
+	defer h.Close()
+
+	droppedframes := 0
+	desyncframes := 0
+
+	CurrentPacket := Frame{}
+	CurrentPacket.Data = make([]byte, 0)
+
+	os.Stdout.WriteString("--myboundary\nContent-Type: image/jpeg\n\n")
+
+	for pkt, r := h.NextEx(); r >= 0; pkt, r = h.NextEx() {
+		if r == 0 {
+			// Timeout, continue
+			continue
+		}
+
+		MACADDR := pkt.Data[0:6]
+		if bytes.Compare(MACADDR, MULTICAST_MAC) != 0 {
+			// This isnt the multicast packet we are looking for
+			continue
+		}
+
+		// Ethernet + IP + UDP = 50, Min packet size is 5 bytes, thus 55
+		if len(pkt.Data) < 100 {
+			continue
+		}
+
+		// Check that the port is 2068
+		if pkt.Data[34] != 0x08 || pkt.Data[35] != 0x14 {
+			continue
+		}
+
+		ApplicationData := pkt.Data[42:]
+
+		FrameNumber := uint16(0)
+		CurrentChunk := uint16(0)
+
+		buf := bytes.NewBuffer(ApplicationData[:2])
+		buf2 := bytes.NewBuffer(ApplicationData[2:4])
+		binary.Read(buf, binary.BigEndian, &FrameNumber)
+		binary.Read(buf2, binary.BigEndian, &CurrentChunk)
+
+		if CurrentPacket.FrameID != FrameNumber && CurrentPacket.FrameID != 0 {
+			// Did we drop a packet ?
+			droppedframes++
+			if CurrentPacket.FrameID < FrameNumber {
+				CurrentPacket = Frame{}
+				CurrentPacket.Data = make([]byte, 0)
+				CurrentPacket.FrameID = CurrentPacket.FrameID
+				CurrentPacket.LastChunk = 0
+				log.Printf("Dropped packet because of non sane frame number (%d dropped so far)", droppedframes)
+			}
+			continue
+		}
+
+		// log.Printf("%d/%d - %d/%d - %d", FrameNumber, CurrentChunk, CurrentPacket.FrameID, CurrentPacket.LastChunk, len(ApplicationData))
+
+		if CurrentPacket.LastChunk != 0 && CurrentPacket.LastChunk != CurrentChunk-1 {
+			if uint16(^(CurrentChunk << 15)) != 65534 {
+				log.Printf("Dropped packet because of desync detected (%d dropped so far, %d because of desync)",
+					droppedframes, desyncframes)
+
+				log.Printf("You see; %d != %d-1",
+					CurrentPacket.LastChunk, CurrentChunk)
+
+				// Oh dear, we are out of sync, Drop the frame
+				droppedframes++
+				desyncframes++
+				CurrentPacket = Frame{}
+				CurrentPacket.Data = make([]byte, 0)
+				CurrentPacket.FrameID = CurrentPacket.FrameID
+				CurrentPacket.LastChunk = 0
+
+				continue
+			}
+			CurrentPacket.LastChunk = CurrentChunk
+		}
+
+		for _, v := range ApplicationData[4:] {
+			CurrentPacket.Data = append(CurrentPacket.Data, v)
+		}
+
+		if uint16(^(CurrentChunk >> 15)) == 65534 {
+			// Flush the frame to output
+			os.Stdout.WriteString("\n--myboundary\nContent-Type: image/jpeg\n\n")
+			log.Printf("Size: %d", len(CurrentPacket.Data))
+			buf := bytes.NewBuffer(CurrentPacket.Data)
+			io.Copy(os.Stdout, buf)
+
+			CurrentPacket = Frame{}
+			CurrentPacket.Data = make([]byte, 0)
+			CurrentPacket.FrameID = 0
+			CurrentPacket.LastChunk = 0
+		}
+
+	}
+}