main.go

// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT

//go:build gocv
// +build gocv

package main

import (
	"bufio"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"image"
	"image/color"
	"io"
	"os"
	"os/exec"
	"runtime"
	"strconv"
	"strings"
	"time"

	"github.com/pion/rtcp"
	"github.com/pion/webrtc/v4"
	"github.com/pion/webrtc/v4/pkg/media/ivfwriter"
	"gocv.io/x/gocv"
)

const (
	frameX      = 960
	frameY      = 720
	frameSize   = frameX * frameY * 3
	minimumArea = 3000
)

func init() {
	// On macOS, NSWindow drag regions should only be invalidated on the Main Thread!
	runtime.LockOSThread()
}

func main() {
	ffmpeg := exec.Command("ffmpeg", "-i", "pipe:0", "-pix_fmt", "bgr24", "-s", strconv.Itoa(frameX)+"x"+strconv.Itoa(frameY), "-f", "rawvideo", "pipe:1") //nolint
	ffmpegIn, _ := ffmpeg.StdinPipe()
	ffmpegOut, _ := ffmpeg.StdoutPipe()
	ffmpegErr, _ := ffmpeg.StderrPipe()

	if err := ffmpeg.Start(); err != nil {
		panic(err)
	}

	go func() {
		scanner := bufio.NewScanner(ffmpegErr)
		for scanner.Scan() {
			fmt.Println(scanner.Text())
		}
	}()

	createWebRTCConn(ffmpegIn)
	startGoCVMotionDetect(ffmpegOut)
}

// This was taken from the GoCV examples, the only change is we are taking a buffer from ffmpeg instead of webcam
// https://github.com/hybridgroup/gocv/blob/master/cmd/motion-detect/main.go
func startGoCVMotionDetect(ffmpegOut io.Reader) {
	window := gocv.NewWindow("Motion Window")
	defer window.Close() //nolint

	img := gocv.NewMat()
	defer img.Close() //nolint

	imgDelta := gocv.NewMat()
	defer imgDelta.Close() //nolint

	imgThresh := gocv.NewMat()
	defer imgThresh.Close() //nolint

	mog2 := gocv.NewBackgroundSubtractorMOG2()
	defer mog2.Close() //nolint

	for {
		buf := make([]byte, frameSize)
		if _, err := io.ReadFull(ffmpegOut, buf); err != nil {
			fmt.Println(err)
			continue
		}
		img, _ := gocv.NewMatFromBytes(frameY, frameX, gocv.MatTypeCV8UC3, buf)
		if img.Empty() {
			continue
		}

		status := "Ready"
		statusColor := color.RGBA{0, 255, 0, 0}

		// first phase of cleaning up image, obtain foreground only
		mog2.Apply(img, &imgDelta)

		// remaining cleanup of the image to use for finding contours.
		// first use threshold
		gocv.Threshold(imgDelta, &imgThresh, 25, 255, gocv.ThresholdBinary)

		// then dilate
		kernel := gocv.GetStructuringElement(gocv.MorphRect, image.Pt(3, 3))
		defer kernel.Close() //nolint
		gocv.Dilate(imgThresh, &imgThresh, kernel)

		// now find contours
		contours := gocv.FindContours(imgThresh, gocv.RetrievalExternal, gocv.ChainApproxSimple)

		for i := 0; i < contours.Size(); i++ {
			area := gocv.ContourArea(contours.At(i))
			if area < minimumArea {
				continue
			}

			status = "Motion detected"
			statusColor = color.RGBA{255, 0, 0, 0}
			gocv.DrawContours(&img, contours, i, statusColor, 2)

			rect := gocv.BoundingRect(contours.At(i))
			gocv.Rectangle(&img, rect, color.RGBA{0, 0, 255, 0}, 2)
		}

		gocv.PutText(&img, status, image.Pt(10, 20), gocv.FontHersheyPlain, 1.2, statusColor, 2)

		window.IMShow(img)
		if window.WaitKey(1) == 27 {
			break
		}
	}
}

func createWebRTCConn(ffmpegIn io.Writer) {
	ivfWriter, err := ivfwriter.NewWith(ffmpegIn)
	if err != nil {
		panic(err)
	}

	// Everything below is the Pion WebRTC API! Thanks for using it ❤️.

	// Prepare the configuration
	config := webrtc.Configuration{
		ICEServers: []webrtc.ICEServer{
			{
				URLs: []string{"stun:stun.l.google.com:19302"},
			},
		},
	}

	// Create a new RTCPeerConnection
	peerConnection, err := webrtc.NewPeerConnection(config)
	if err != nil {
		panic(err)
	}

	// Set a handler for when a new remote track starts, this handler copies inbound RTP packets,
	// replaces the SSRC and sends them back
	peerConnection.OnTrack(func(track *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
		if track.Kind() == webrtc.RTPCodecTypeVideo {
			// Send a PLI on an interval so that the publisher is pushing a keyframe every rtcpPLIInterval
			go func() {
				ticker := time.NewTicker(time.Second * 3)
				for range ticker.C {
					errSend := peerConnection.WriteRTCP([]rtcp.Packet{&rtcp.PictureLossIndication{MediaSSRC: uint32(track.SSRC())}})
					if errSend != nil {
						fmt.Println(errSend)
					}
				}
			}()
		}

		fmt.Printf("Track has started, of type %d: %s \n", track.PayloadType(), track.Codec().RTPCodecCapability.MimeType)
		for {
			// Read RTP packets being sent to Pion
			rtp, _, readErr := track.ReadRTP()
			if readErr != nil {
				panic(readErr)
			}

			if ivfWriterErr := ivfWriter.WriteRTP(rtp); ivfWriterErr != nil {
				panic(ivfWriterErr)
			}
		}
	})
	// Set the handler for ICE connection state
	// This will notify you when the peer has connected/disconnected
	peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
		fmt.Printf("Connection State has changed %s \n", connectionState.String())
	})

	// Wait for the offer to be pasted
	offer := webrtc.SessionDescription{}
	decode(readUntilNewline(), &offer)

	// Set the remote SessionDescription
	err = peerConnection.SetRemoteDescription(offer)
	if err != nil {
		panic(err)
	}

	// Create an answer
	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		panic(err)
	}

	// Create channel that is blocked until ICE Gathering is complete
	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)

	// Sets the LocalDescription, and starts our UDP listeners
	err = peerConnection.SetLocalDescription(answer)
	if err != nil {
		panic(err)
	}

	// Block until ICE Gathering is complete, disabling trickle ICE
	// we do this because we only can exchange one signaling message
	// in a production application you should exchange ICE Candidates via OnICECandidate
	<-gatherComplete

	// Output the answer in base64 so we can paste it in browser
	fmt.Println(encode(peerConnection.LocalDescription()))
}

// Read from stdin until we get a newline
func readUntilNewline() (in string) {
	var err error

	r := bufio.NewReader(os.Stdin)
	for {
		in, err = r.ReadString('\n')
		if err != nil && !errors.Is(err, io.EOF) {
			panic(err)
		}

		if in = strings.TrimSpace(in); len(in) > 0 {
			break
		}
	}

	fmt.Println("")
	return
}

// JSON encode + base64 a SessionDescription
func encode(obj *webrtc.SessionDescription) string {
	b, err := json.Marshal(obj)
	if err != nil {
		panic(err)
	}

	return base64.StdEncoding.EncodeToString(b)
}

// Decode a base64 and unmarshal JSON into a SessionDescription
func decode(in string, obj *webrtc.SessionDescription) {
	b, err := base64.StdEncoding.DecodeString(in)
	if err != nil {
		panic(err)
	}

	if err = json.Unmarshal(b, obj); err != nil {
		panic(err)
	}
}