tello: can stream drone video thru to opencv

Signed-off-by: Ron Evans <ron@hybridgroup.com>

examples/tello_opencv.go

@@ -0,0 +1,86 @@
+// +build example
+//
+// Do not build by default.
+
+/*
+You must have ffmpeg and ffplay installed in order to run this code. it will connect to the Tello
+and then open a window using ffplay showing the streaming video.
+
+How to run
+
+	go run examples/tello_opencv.go
+*/
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"os/exec"
+	"time"
+
+	"gobot.io/x/gobot"
+	"gobot.io/x/gobot/platforms/dji/tello"
+	"gobot.io/x/gobot/platforms/opencv"
+	"gocv.io/x/gocv"
+)
+
+const (
+	frameSize = 960 * 720 * 3
+)
+
+func main() {
+	drone := tello.NewDriver("8890")
+	window := opencv.NewWindowDriver()
+
+	work := func() {
+		ffmpeg := exec.Command("ffmpeg", "-i", "pipe:0", "-pix_fmt", "bgr24", "-vcodec", "rawvideo",
+			"-an", "-sn", "-f", "rawvideo", "pipe:1")
+		ffmpegIn, _ := ffmpeg.StdinPipe()
+		ffmpegOut, _ := ffmpeg.StdoutPipe()
+		if err := ffmpeg.Start(); err != nil {
+			fmt.Println(err)
+			return
+		}
+
+		go func() {
+			for {
+				buf := make([]byte, frameSize)
+				if _, err := io.ReadFull(ffmpegOut, buf); err != nil {
+					fmt.Println(err)
+					continue
+				}
+
+				img := gocv.NewMatFromBytes(720, 960, gocv.MatTypeCV8UC3, buf)
+				if img.Empty() {
+					continue
+				}
+				window.ShowImage(img)
+				window.WaitKey(1)
+			}
+		}()
+
+		drone.On(tello.ConnectedEvent, func(data interface{}) {
+			fmt.Println("Connected")
+			drone.StartVideo()
+			gobot.Every(1*time.Second, func() {
+				drone.StartVideo()
+			})
+		})
+
+		drone.On(tello.VideoFrameEvent, func(data interface{}) {
+			pkt := data.([]byte)
+			if _, err := ffmpegIn.Write(pkt); err != nil {
+				fmt.Println(err)
+			}
+		})
+	}
+
+	robot := gobot.NewRobot("tello",
+		[]gobot.Connection{},
+		[]gobot.Device{drone, window},
+		work,
+	)
+
+	robot.Start()
+}

platforms/dji/tello/README.md

@@ -59,3 +59,5 @@ https://tellopilots.com/forums/tello-development.8/
 Special thanks to [@Kragrathea](https://github.com/Kragrathea) who figured out a LOT of the packets and code as implemented in C#: [https://github.com/Kragrathea/TelloPC](https://github.com/Kragrathea/TelloPC)
 
 Also thanks to [@microlinux](https://github.com/microlinux) with the Python library which served as the first example for the Tello community: [https://github.com/microlinux/tello](https://github.com/microlinux/tello)
+
+Thank you to bluejune for the [https://bitbucket.org/PingguSoft/pytello](https://bitbucket.org/PingguSoft/pytello) repo, especially the Wireshark Lua dissector which has proven indispensable.