revid & cmd/revid-cli: added loop mode so that input may be restarted after completion

Loop flag has been added to command line flags and in turn sets the Loop field that has been
added to the config.Config struct. mode variable now also checked to see if value set to
Loop, in which case revid config.Config.Loop = true. Revid.processFrom modified so that
when input source has completed Revid.cfg.Loop is checked and input restarted if true.

cmd/revid-cli/main.go

@@ -122,6 +122,7 @@ func handleFlags() config.Config {
 		httpAddressPtr      = flag.String("HttpAddress", "", "Destination address of http posts")
 		verticalFlipPtr     = flag.Bool("VerticalFlip", false, "Flip video vertically: Yes, No")
 		horizontalFlipPtr   = flag.Bool("HorizontalFlip", false, "Flip video horizontally: Yes, No")
+		loopPtr             = flag.Bool("Loop", false, "Loop video if EOF encountered: true, false")
 		bitratePtr          = flag.Uint("Bitrate", 0, "Bitrate of recorded video")
 		heightPtr           = flag.Uint("Height", 0, "Height in pixels")
 		widthPtr            = flag.Uint("Width", 0, "Width in pixels")
@@ -179,6 +180,8 @@ func handleFlags() config.Config {
 		}
 	}
 
+	cfg.Loop = *loopPtr
+
 	switch *inputPtr {
 	case "Raspivid":
 		cfg.Input = config.InputRaspivid

revid/config/config.go

@@ -297,6 +297,9 @@ type Config struct {
 	MOGMinArea   float64 // Used to ignore small areas of motion detection.
 	MOGThreshold float64 // Intensity value from the KNN motion detection algorithm that is considered motion.
 	MOGHistory   uint    // Length of MOG filter's history
+
+	// If true will restart reading of input after an io.EOF.
+	Loop bool
 }
 
 // TypeData contains information about all of the variables that

revid/revid.go

@@ -428,13 +428,8 @@ func (r *Revid) Start() error {
 		return err
 	}
 
-	err = r.input.Start()
-	if err != nil {
-		return fmt.Errorf("could not start input device: %w", err)
-	}
-
 	r.wg.Add(1)
-	go r.processFrom(r.input, 0)
+	go r.processFrom(r.input, (1000/25)*time.Millisecond)
 
 	r.running = true
 	return nil
@@ -845,6 +840,11 @@ func (r *Revid) Update(vars map[string]string) error {
 				break
 			}
 			r.cfg.MOGHistory = uint(v)
+		case "mode":
+			r.cfg.Loop = false
+			if value == "Loop" {
+				r.cfg.Loop = true
+			}
 		}
 	}
 	r.cfg.Logger.Log(logger.Info, pkg+"revid config changed", "config", fmt.Sprintf("%+v", r.cfg))
@@ -853,14 +853,35 @@ func (r *Revid) Update(vars map[string]string) error {
 
 // processFrom is run as a routine to read from a input data source, lex and
 // then send individual access units to revid's encoders.
-func (r *Revid) processFrom(read io.Reader, delay time.Duration) {
-	err := r.lexTo(r.filters[0], read, delay)
-	r.cfg.Logger.Log(logger.Debug, pkg+"finished lexing")
+func (r *Revid) processFrom(in device.AVDevice, delay time.Duration) {
+restart:
+	err := in.Start()
+	if err != nil {
+		r.err <- fmt.Errorf("could not start input device: %w", err)
+		r.wg.Done()
+		return
+	}
+
+	// Lex data from input device, in, until finished or an error is encountered.
+	// For a continuous source e.g. a camera or microphone, we should remain
+	// in this call indefinitely unless in.Stop() is called and an io.EOF is forced.
+	err = r.lexTo(r.filters[0], in, delay)
 	switch err {
-	case nil: // Do nothing.
-	case io.EOF: // TODO: handle this depending on loop mode.
+	case nil, io.EOF, io.ErrUnexpectedEOF:
 	default:
 		r.err <- err
 	}
+
+	err = in.Stop()
+	if err != nil {
+		r.err <- fmt.Errorf("could not stop input source: %w", err)
+	}
+
+	if r.cfg.Loop {
+		r.cfg.Logger.Log(logger.Info, pkg+"looping input")
+		goto restart
+	}
+
+	r.cfg.Logger.Log(logger.Info, pkg+"finished lexing")
 	r.wg.Done()
 }