Added capture example

Author: djthorpe

cmd/examples/capture/context.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"context"
+	"os"
+	"os/signal"
+)
+
+///////////////////////////////////////////////////////////////////////////////
+// PUBLIC METHODS
+
+// ContextForSignal returns a context object which is cancelled when a signal
+// is received. It returns nil if no signal parameter is provided
+func ContextForSignal(signals ...os.Signal) context.Context {
+	if len(signals) == 0 {
+		return nil
+	}
+
+	ch := make(chan os.Signal, 1)
+	ctx, cancel := context.WithCancel(context.Background())
+
+	// Send message on channel when signal received
+	signal.Notify(ch, signals...)
+
+	// When any signal received, call cancel
+	go func() {
+		<-ch
+		cancel()
+	}()
+
+	// Return success
+	return ctx
+}

cmd/examples/capture/main.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+	"fmt"
+	"image/jpeg"
+	"log"
+	"os"
+	"regexp"
+	"syscall"
+
+	// Packages
+	media "github.com/mutablelogic/go-media"
+	ffmpeg "github.com/mutablelogic/go-media/pkg/ffmpeg"
+)
+
+var (
+	reDeviceNamePath = regexp.MustCompile(`^([a-z][a-zA-Z0-9]+)\:(.*)$`)
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		log.Fatal("Usage: capture device:path")
+	}
+
+	// Get the format associated with the input file
+	device := reDeviceNamePath.FindStringSubmatch(os.Args[1])
+	if device == nil {
+		log.Fatal("Invalid device name, use device:path")
+	}
+
+	// Create a media manager
+	manager, err := ffmpeg.NewManager(ffmpeg.OptLog(false, nil))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Find device
+	devices := manager.Formats(media.DEVICE, device[1])
+	if len(devices) == 0 {
+		log.Fatalf("No devices found for %v", device[1])
+	}
+	if len(devices) > 1 {
+		log.Fatalf("Multiple devices found: %q", devices)
+	}
+
+	// Open device
+	media, err := manager.Open(device[2], devices[0])
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer media.Close()
+
+	// Tmpdir
+	tmpdir, err := os.MkdirTemp("", "capture")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Frame function
+	frameFunc := func(stream int, frame *ffmpeg.Frame) error {
+		w, err := os.Create(fmt.Sprintf("%v/frame-%v.jpg", tmpdir, frame.Ts()))
+		if err != nil {
+			return err
+		}
+		defer w.Close()
+
+		image, err := frame.Image()
+		if err != nil {
+			return err
+		}
+
+		if err := jpeg.Encode(w, image, nil); err != nil {
+			return err
+		}
+
+		fmt.Println("Written", w.Name())
+
+		return nil
+	}
+
+	// Map function
+	mapFunc := func(_ int, in *ffmpeg.Par) (*ffmpeg.Par, error) {
+		fmt.Println("Input", in)
+		return ffmpeg.VideoPar("yuv420p", in.WidthHeight(), in.FrameRate()), nil
+	}
+
+	// Receive frames
+	if err := media.(*ffmpeg.Reader).Decode(
+		ContextForSignal(os.Interrupt, syscall.SIGQUIT),
+		mapFunc,
+		frameFunc,
+	); err != nil {
+		log.Fatal(err)
+	}
+}