Created motion filter that has a minimum frame rate.

filter/variable_fps.go

@@ -0,0 +1,68 @@
+/*
+DESCRIPTION
+  A motion filter that has a variable frame rate. When motion is detected,
+  the filter sends all frames and when it is not, the filter sends frames
+  at a reduced rate, as set by a parameter.
+
+AUTHORS
+  Scott Barnard <scott@ausocean.org>
+
+LICENSE
+  variable_fps.go is Copyright (C) 2019 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 (
+	"io"
+)
+
+// VariableFps is a filter that has a variable frame rate. When motion is
+// detected, the filter sends all frames and when it is not, the filter
+// sends frames at a reduced framerate.
+type VariableFps struct {
+	motionFilter Filter
+	dst          io.WriteCloser
+	frames       uint
+	count        uint
+}
+
+// NewVariableFps returns a pointer to a new VariableFps filter.
+func NewVariableFps(dst io.WriteCloser, fps float64) *VariableFps {
+	frames := uint(25 / fps)
+	mf := NewMOGFilter(dst, 25, 20, 500, 3, true)
+	return &VariableFps{mf, dst, frames, 0}
+}
+
+// Implements io.Writer.
+// Write applies the motion filter to the video stream. Frames are sent
+// at a reduced frame rate, except when motion is detected, then all frames
+// with motion are sent.
+func (v *VariableFps) Write(f []byte) (int, error) {
+	v.count++
+	if v.count > v.frames {
+		v.count = 0
+		return v.dst.Write(f)
+	}
+
+	return v.motionFilter.Write(f)
+}
+
+// Implements io.Closer.
+// Close calls the motion filter's Close method.
+func (v *VariableFps) Close() error {
+	return v.motionFilter.Close()
+}

revid/config/config.go

@@ -112,6 +112,7 @@ const (
 const (
 	FilterNoOp = iota
 	FilterMOG
+	FilterVariableFPS
 )
 
 // Config provides parameters relevant to a revid instance. A new config must

revid/revid.go

@@ -333,6 +333,8 @@ func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.
 		r.filter = filter.NewNoOp(r.encoders)
 	case config.FilterMOG:
 		r.filter = filter.NewMOGFilter(r.encoders, 25, 20, 500, 3, true)
+	case config.FilterVariableFPS:
+		r.filter = filter.NewVariableFps(r.encoders, 1.0)
 	default:
 		panic("Undefined Filter")
 	}
@@ -630,7 +632,7 @@ func (r *Revid) Update(vars map[string]string) error {
 				r.cfg.Logger.Log(logger.Warning, pkg+"invalid VerticalFlip param", "value", value)
 			}
 		case "Filter":
-			m := map[string]int{"NoOp": config.FilterNoOp, "MOG": config.FilterMOG}
+			m := map[string]int{"NoOp": config.FilterNoOp, "MOG": config.FilterMOG, "VariableFPS": config.FilterVariableFPS}
 			v, ok := m[value]
 			if !ok {
 				r.cfg.Logger.Log(logger.Warning, pkg+"invalid FilterMethod param", "value", value)