Camera timeout duration as parameter (#408)

Set PION_MEDIADEVICES_CAMERA_READ_TIMEOUT environment variable
to set the timeout duration.

pkg/driver/camera/camera_linux.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strconv"
 	"sync"
 
 	"github.com/blackjack/webcam"
@@ -133,6 +134,19 @@ func newCamera(path string) *camera {
 	return c
 }
 
+func getCameraReadTimeout() uint32 {
+	// default to 5 seconds
+	var readTimeoutSec uint32 = 5
+	if val, ok := os.LookupEnv("PION_MEDIADEVICES_CAMERA_READ_TIMEOUT"); ok {
+		if valInt, err := strconv.Atoi(val); err == nil {
+			if valInt > 0 {
+				readTimeoutSec = uint32(valInt)
+			}
+		}
+	}
+	return readTimeoutSec
+}
+
 func (c *camera) Open() error {
 	cam, err := webcam.Open(c.path)
 	if err != nil {
@@ -192,6 +206,8 @@ func (c *camera) VideoRecord(p prop.Media) (video.Reader, error) {
 
 	cam := c.cam
 
+	readTimeoutSec := getCameraReadTimeout()
+
 	ctx, cancel := context.WithCancel(context.Background())
 	c.cancel = cancel
 	var buf []byte
@@ -207,7 +223,7 @@ func (c *camera) VideoRecord(p prop.Media) (video.Reader, error) {
 				return nil, func() {}, io.EOF
 			}
 
-			err := cam.WaitForFrame(5) // 5 seconds
+			err := cam.WaitForFrame(readTimeoutSec)
 			switch err.(type) {
 			case nil:
 			case *webcam.Timeout:

pkg/driver/camera/camera_linux_test.go

@@ -70,3 +70,31 @@ func TestDiscover(t *testing.T) {
 		t.Errorf("Expected label: %s, got: %s", expectedNoLink, label)
 	}
 }
+
+func TestGetCameraReadTimeout(t *testing.T) {
+	var expected uint32 = 5
+	value := getCameraReadTimeout()
+	if value != expected {
+		t.Errorf("Expected: %d, got: %d", expected, value)
+	}
+
+	envVarName := "PION_MEDIADEVICES_CAMERA_READ_TIMEOUT"
+	os.Setenv(envVarName, "text")
+	value = getCameraReadTimeout()
+	if value != expected {
+		t.Errorf("Expected: %d, got: %d", expected, value)
+	}
+
+	os.Setenv(envVarName, "-1")
+	value = getCameraReadTimeout()
+	if value != expected {
+		t.Errorf("Expected: %d, got: %d", expected, value)
+	}
+
+	os.Setenv(envVarName, "1")
+	expected = 1
+	value = getCameraReadTimeout()
+	if value != expected {
+		t.Errorf("Expected: %d, got: %d", expected, value)
+	}
+}