filter: create a simple difference motion filter using gocv

filter/difference.go

@@ -0,0 +1,114 @@
+// +build !circleci
+
+/*
+DESCRIPTION
+  A filter that detects motion and discards frames without motion. The
+  algorithm calculates the absolute difference for each pixel between
+  two frames, then finds the mean. If the mean is above a given threshold,
+  then it is considered motion.
+
+AUTHORS
+  Scott Barnard <scott@ausocean.org>
+
+LICENSE
+  difference.go is Copyright (C) 2020 the Australian Ocean Lab (AusOcean)
+
+  It is free software: you can redistribute it and/or modify them
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+  for more details.
+
+  You should have received a copy of the GNU General Public License
+  in gpl.txt.  If not, see http://www.gnu.org/licenses.
+*/
+
+package filter
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"io"
+
+	"gocv.io/x/gocv"
+)
+
+// DiffFilter is a filter that provides basic motion detection. DiffFilter calculates
+// the absolute difference for each pixel between two frames, then finds the mean. If
+// the mean is above a given threshold, then it is considered motion.
+type DiffFilter struct {
+	dst     io.WriteCloser
+	thresh  float64
+	prev    gocv.Mat
+	debug   bool
+	windows []*gocv.Window
+}
+
+// NewDiffFilter returns a pointer to a new DiffFilter.
+func NewDiffFilter(dst io.WriteCloser, debug bool, threshold float64) *DiffFilter {
+	var windows []*gocv.Window
+	if debug {
+		windows = []*gocv.Window{gocv.NewWindow("Diff: Bounding boxes"), gocv.NewWindow("Diff: Motion")}
+	}
+	return &DiffFilter{dst, threshold, gocv.NewMat(), debug, windows}
+}
+
+// Implements io.Closer.
+// Close frees resources used by gocv, because it has to be done manually, due to
+// it using c-go.
+func (d *DiffFilter) Close() error {
+	d.prev.Close()
+	for _, window := range d.windows {
+		window.Close()
+	}
+	return nil
+}
+
+// Implements io.Writer.
+// Write applies the motion filter to the video stream. Only frames with motion
+// are written to the destination encoder, frames without are discarded.
+func (d *DiffFilter) Write(f []byte) (int, error) {
+	if d.prev.Empty() {
+		d.prev, _ = gocv.IMDecode(f, gocv.IMReadColor)
+		return 0, nil
+	}
+
+	img, _ := gocv.IMDecode(f, gocv.IMReadColor)
+	defer img.Close()
+
+	imgDelta := gocv.NewMat()
+	defer imgDelta.Close()
+
+	// Seperate foreground and background.
+	gocv.AbsDiff(img, d.prev, &imgDelta)
+	gocv.CvtColor(imgDelta, &imgDelta, gocv.ColorBGRToGray)
+
+	mean := imgDelta.Mean().Val1
+
+	// Update History
+	d.prev = img.Clone()
+
+	// Draw debug information.
+	if d.debug {
+		if mean >= d.thresh {
+			gocv.PutText(&img, fmt.Sprintf("motion - mean:%f", mean), image.Pt(32, 32), gocv.FontHersheyPlain, 2.0, color.RGBA{255, 0, 0, 0}, 2)
+		}
+
+		d.windows[0].IMShow(img)
+		d.windows[1].IMShow(imgDelta)
+		d.windows[0].WaitKey(1)
+	}
+
+	// Don't write to destination if there is no motion.
+	if mean < d.thresh {
+		return 0, nil
+	}
+
+	// Write to destination.
+	return d.dst.Write(f)
+}

revid/config/config.go

@@ -127,6 +127,7 @@ const (
 	FilterMOG
 	FilterVariableFPS
 	FilterKNN
+	FilterDifference
 )
 
 // OS names
@@ -304,6 +305,8 @@ type Config struct {
 
 	// Defines the rate at which frames from a file source are processed.
 	FileFPS int
+	// Difference filter parameters.
+	DiffThreshold float64 // Intensity value from the Difference motion detection algorithm that is considered motion.
 }
 
 // TypeData contains information about all of the variables that
@@ -317,9 +320,10 @@ var TypeData = map[string]string{
 	"CameraIP":         "string",
 	"CBR":              "bool",
 	"ClipDuration":     "uint",
+	"DiffThreshold":    "float",
 	"Exposure":         "enum:auto,night,nightpreview,backlight,spotlight,sports,snow,beach,verylong,fixedfps,antishake,fireworks",
 	"FileFPS":          "int",
-	"Filters":          "enums:NoOp,MOG,VariableFPS,KNN",
+	"Filters":          "enums:NoOp,MOG,VariableFPS,KNN,Difference",
 	"FrameRate":        "uint",
 	"Height":           "uint",
 	"HorizontalFlip":   "bool",
@@ -340,13 +344,13 @@ var TypeData = map[string]string{
 	"MOGMinArea":       "float",
 	"MOGThreshold":     "float",
 	"MotionInterval":   "int",
-	"RBCapacity":       "uint",
-	"RBMaxElements":    "uint",
-	"RBWriteTimeout":   "uint",
 	"Output":           "enum:File,Http,Rtmp,Rtp",
 	"OutputPath":       "string",
 	"Outputs":          "enums:File,Http,Rtmp,Rtp",
 	"Quantization":     "uint",
+	"RBCapacity":       "uint",
+	"RBMaxElements":    "uint",
+	"RBWriteTimeout":   "uint",
 	"Rotation":         "uint",
 	"RTMPURL":          "string",
 	"RTPAddress":       "string",

revid/revid.go

@@ -342,6 +342,8 @@ func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.
 				r.filters[i] = filter.NewVariableFPSFilter(dst, r.cfg.MinFPS, filter.NewMOGFilter(dst, r.cfg.MOGMinArea, r.cfg.MOGThreshold, int(r.cfg.MOGHistory), r.cfg.ShowWindows, r.cfg.MotionInterval))
 			case config.FilterKNN:
 				r.filters[i] = filter.NewKNNFilter(dst, r.cfg.KNNMinArea, r.cfg.KNNThreshold, int(r.cfg.KNNHistory), int(r.cfg.KNNKernel), r.cfg.ShowWindows, r.cfg.MotionInterval)
+			case config.FilterDifference:
+				r.filters[i] = filter.NewDiffFilter(dst, r.cfg.ShowWindows, r.cfg.DiffThreshold)
 			default:
 				panic("Undefined Filter")
 			}
@@ -663,7 +665,7 @@ func (r *Revid) Update(vars map[string]string) error {
 			}
 		case "Filters":
 			filters := strings.Split(value, ",")
-			m := map[string]int{"NoOp": config.FilterNoOp, "MOG": config.FilterMOG, "VariableFPS": config.FilterVariableFPS, "KNN": config.FilterKNN}
+			m := map[string]int{"NoOp": config.FilterNoOp, "MOG": config.FilterMOG, "VariableFPS": config.FilterVariableFPS, "KNN": config.FilterKNN, "Difference": config.FilterDifference}
 			r.cfg.Filters = make([]int, len(filters))
 			for i, filter := range filters {
 				v, ok := m[filter]
@@ -811,6 +813,13 @@ func (r *Revid) Update(vars map[string]string) error {
 				break
 			}
 			r.cfg.KNNThreshold = v
+		case "DiffThreshold":
+			v, err := strconv.ParseFloat(value, 64)
+			if err != nil {
+				r.cfg.Logger.Log(logger.Warning, pkg+"invalid DiffThreshold var", "value", value)
+				break
+			}
+			r.cfg.DiffThreshold = v
 		case "KNNKernel":
 			v, err := strconv.Atoi(value)
 			if err != nil {