Added multiplatform webcam streaming

camera.go

@@ -0,0 +1,184 @@
+package main
+
+import (
+	"io"
+	"os"
+	"os/exec"
+	"os/signal"
+	"runtime"
+	"strconv"
+	"syscall"
+)
+
+type Camera struct {
+	name        string
+	width       int
+	height      int
+	depth       int
+	fps         float64
+	codec       string
+	framebuffer []byte
+	pipe        *io.ReadCloser
+	cmd         *exec.Cmd
+}
+
+func getDevicesWindows() []string {
+	// Run command to get list of devices.
+	cmd := exec.Command(
+		"ffmpeg",
+		"-hide_banner",
+		"-list_devices", "true",
+		"-f", "dshow",
+		"-i", "dummy",
+	)
+	pipe, err := cmd.StderrPipe()
+	if err != nil {
+		panic(err)
+	}
+	if err := cmd.Start(); err != nil {
+		panic(err)
+	}
+	// Read list devices from Stdout.
+	buffer := make([]byte, 2<<10)
+	total := 0
+	for {
+		n, err := pipe.Read(buffer[total:])
+		total += n
+		if err == io.EOF {
+			break
+		}
+	}
+	cmd.Wait()
+	devices := parseDevices(buffer)
+	return devices
+}
+
+func getCameraData(device string, camera *Camera) {
+	// Run command to get camera data.
+	// On windows the webcam will turn on and off again.
+	cmd := exec.Command(
+		"ffmpeg",
+		"-hide_banner",
+		"-f", webcam(),
+		"-i", device,
+	)
+
+	pipe, err := cmd.StderrPipe()
+	if err != nil {
+		panic(err)
+	}
+
+	if err := cmd.Start(); err != nil {
+		panic(err)
+	}
+	// Read ffmpeg output from Stdout.
+	buffer := make([]byte, 2<<11)
+	total := 0
+	for {
+		n, err := pipe.Read(buffer[total:])
+		total += n
+		if err == io.EOF {
+			break
+		}
+	}
+
+	cmd.Wait()
+
+	parseWebcamData(buffer[:total], camera)
+}
+
+func NewCamera(stream int) *Camera {
+	checkExists("ffmpeg")
+
+	var device string
+	// If OS is windows, we need to parse the listed devices to find which corresponds to the
+	// given "stream" index.
+	switch runtime.GOOS {
+	case "linux":
+		device = "/dev/video" + strconv.Itoa(stream)
+		break
+	case "darwin":
+		device = strconv.Itoa(stream)
+		break
+	case "windows":
+		devices := getDevicesWindows()
+		if stream >= len(devices) {
+			panic("Could not find devices with index: " + strconv.Itoa(stream))
+		}
+		device = "video=" + devices[stream]
+		break
+	}
+
+	camera := &Camera{name: device, depth: 3}
+	getCameraData(device, camera)
+
+	return camera
+}
+
+func initCamera(camera *Camera) {
+	// If user exits with Ctrl+C, stop ffmpeg process.
+	camera.cleanup()
+
+	// Use ffmpeg to pipe webcam to stdout.
+	cmd := exec.Command(
+		"ffmpeg",
+		"-hide_banner",
+		"-f", webcam(),
+		"-i", camera.name,
+		"-f", "image2pipe",
+		"-loglevel", "quiet",
+		"-pix_fmt", "rgb24",
+		"-vcodec", "rawvideo", "-",
+	)
+
+	camera.cmd = cmd
+	pipe, err := cmd.StdoutPipe()
+	if err != nil {
+		panic(err)
+	}
+
+	camera.pipe = &pipe
+	if err := cmd.Start(); err != nil {
+		panic(err)
+	}
+	camera.framebuffer = make([]byte, camera.width*camera.height*camera.depth)
+}
+
+func (camera *Camera) NextFrame() bool {
+	// If cmd is nil, video reading has not been initialized.
+	if camera.cmd == nil {
+		initCamera(camera)
+	}
+	total := 0
+	for total < camera.width*camera.height*camera.depth {
+		n, _ := (*camera.pipe).Read(camera.framebuffer[total:])
+		total += n
+	}
+	return true
+}
+
+func (camera *Camera) Close() {
+	if camera.pipe != nil {
+		(*camera.pipe).Close()
+	}
+	if camera.cmd != nil {
+		camera.cmd.Process.Kill()
+	}
+}
+
+// Stops the "cmd" process running when the user presses Ctrl+C.
+// https://stackoverflow.com/questions/11268943/is-it-possible-to-capture-a-ctrlc-signal-and-run-a-cleanup-function-in-a-defe
+func (camera *Camera) cleanup() {
+	c := make(chan os.Signal)
+	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-c
+		if camera.pipe != nil {
+			(*camera.pipe).Close()
+		}
+		if camera.cmd != nil {
+			camera.cmd.Process.Kill()
+		}
+		os.Exit(1)
+	}()
+}