revid/webcam.go: started writing implementation of AVDevice for webcams

revid/webcam.go

@@ -0,0 +1,80 @@
+/*
+DESCRIPTION
+  webcam.go provides an implementation of AVDevice for webcams.
+
+AUTHORS
+  Saxon A. Nelson-Milton <saxon@ausocean.org>
+
+LICENSE
+  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 revid
+
+import (
+	"errors"
+	"io"
+)
+
+const (
+	defaultWebcamInputPath = "/dev/video0"
+	defaultWebcamFrameRate = 25
+	defaultWebcamBitrate   = 400
+	defaultWebcamWidth     = 1280
+	defaultWebcamHeight    = 720
+)
+
+var (
+	errWebcamBadFrameRate = errors.New("frame rate bad or unset, defaulting")
+	errWebcamBadBitrate   = errors.New("bitrate bad or unset, defaulting")
+	errWebcamWidth        = errors.New("width bad or unset, defaulting")
+	errWebcamHeight       = errors.New("height bad or unset, defaulting")
+)
+
+type Webcam struct {
+	out io.ReadCloser
+	log Logger
+	cfg Config
+}
+
+func NewWebcam(l Logger) *Webcam {
+	return &Webcam{log: l}
+}
+
+func (w *Webcam) Set(c Config) error {
+	var errs []error
+	if c.Width == 0 {
+		errs = append(errs, errBadWidth)
+		c.Width = raspividDefaultWidth
+	}
+
+	if c.Height == 0 {
+		errs = append(errs, errBadHeight)
+		c.Height = raspividDefaultHeight
+	}
+
+	if c.FrameRate == 0 {
+		errs = append(errs, errBadFrameRate)
+		c.FrameRate = raspividDefaultFramerate
+	}
+
+	if c.Bitrate <= 0 {
+		errs = append(errs, errBadBitrate)
+		c.Bitrate = raspividDefaultBitrate
+	}
+	w.cfg = c
+	return multiError(errs)
+}