diff --git a/cmd/rv/main.go b/cmd/rv/main.go
index ce75a7e7..7b6e4c85 100644
--- a/cmd/rv/main.go
+++ b/cmd/rv/main.go
@@ -55,6 +55,7 @@ USAGE
 package main
 
 import (
+	"bytes"
 	"io"
 	"os"
 	"runtime/pprof"
@@ -72,7 +73,6 @@ import (
 	"bitbucket.org/ausocean/av/turbidity"
 	"bitbucket.org/ausocean/iot/pi/netlogger"
 	"bitbucket.org/ausocean/iot/pi/netsender"
-	"bitbucket.org/ausocean/iot/pi/sds"
 	"bitbucket.org/ausocean/utils/logger"
 )
 
@@ -135,6 +135,7 @@ type turbidityProbe struct {
 	ticker              time.Ticker
 	ts                  *turbidity.TurbiditySensor
 	log                 logger.Logger
+	buffer              *bytes.Buffer
 }
 
 // NewTurbidityProbe returns a new turbidity probe.
@@ -143,6 +144,7 @@ func NewTurbidityProbe(log logger.Logger, delay time.Duration) (*turbidityProbe,
 	tp.log = log
 	tp.delay = delay
 	tp.ticker = *time.NewTicker(delay)
+	tp.buffer = bytes.NewBuffer(*new([]byte))
 
 	// Create the turbidity sensor.
 	standard := gocv.IMRead("../../turbidity/images/template.jpg", gocv.IMReadGrayScale)
@@ -158,6 +160,7 @@ func NewTurbidityProbe(log logger.Logger, delay time.Duration) (*turbidityProbe,
 // Write, reads input h264 frames in the form of a byte stream and writes the the sharpness and contrast
 // scores of a video to the the turbidity probe.
 func (tp *turbidityProbe) Write(p []byte) (int, error) {
+	tp.buffer.Write(p)
 	select {
 	case <-tp.ticker.C:
 		var imgs []gocv.Mat
@@ -170,12 +173,12 @@ func (tp *turbidityProbe) Write(p []byte) (int, error) {
 			return len(p), err
 		}
 		defer os.Remove(file.Name())
-		_, err = file.Write(p)
+		_, err = file.Write(tp.buffer.Bytes())
 		if err != nil {
 			tp.log.Error("failed to write to temporary file", "error", err.Error())
 			return len(p), err
 		}
-
+		tp.buffer.Reset()
 		// Read the file and store each frame.
 		vc, err := gocv.VideoCaptureFile(file.Name())
 		if err != nil {
@@ -185,11 +188,15 @@ func (tp *turbidityProbe) Write(p []byte) (int, error) {
 		for vc.Read(&img) && len(imgs) < maxImages {
 			imgs = append(imgs, img.Clone())
 		}
+		if len(imgs) <= 0 {
+			tp.log.Log(logger.Info, "no frames found")
+			return len(p), nil
+		}
 
 		// Process video data to get saturation and contrast scores.
 		res, err := tp.ts.Evaluate(imgs)
 		if err != nil {
-			tp.log.Error("evaluate failed", "errror", err.Error())
+			tp.log.Error("evaluate failed", "error", err.Error())
 			return len(p), err
 		}
 		tp.contrast = stat.Mean(res.Contrast, nil)
@@ -236,7 +243,7 @@ func main() {
 	p, err := NewTurbidityProbe(*log, 60*time.Second)
 
 	log.Log(logger.Debug, "initialising netsender client")
-	ns, err := netsender.New(log, nil, readPin(p, rv), nil, createVarMap())
+	ns, err := netsender.New(log, nil, readPin(p, rv, log), nil, createVarMap())
 	if err != nil {
 		log.Log(logger.Fatal, pkg+"could not initialise netsender client: "+err.Error())
 	}
@@ -375,7 +382,7 @@ func sleep(ns *netsender.Sender, l *logger.Logger) {
 
 // readPin provides a callback function of consistent signature for use by
 // netsender to retrieve software defined pin values e.g. revid bitrate.
-func readPin(p *turbidityProbe, rv *revid.Revid) func(pin *netsender.Pin) error {
+func readPin(p *turbidityProbe, rv *revid.Revid, l *logger.Logger) func(pin *netsender.Pin) error {
 	return func(pin *netsender.Pin) error {
 		switch {
 		case pin.Name == bitratePin:
@@ -383,16 +390,16 @@ func readPin(p *turbidityProbe, rv *revid.Revid) func(pin *netsender.Pin) error
 			if rv != nil {
 				pin.Value = rv.Bitrate()
 			}
-		case pin.Name[0] == 'X':
-			return sds.ReadSystem(pin)
 		case pin.Name == sharpnessPin:
 			pin.Value = -1
 			if p != nil {
+				l.Debug("setting sharpness value", "sharpness", p.sharpness*1000)
 				pin.Value = int(p.sharpness * 1000)
 			}
 		case pin.Name == contrastPin:
 			pin.Value = -1
 			if p != nil {
+				l.Debug("setting contrast pin", "contrast", p.contrast)
 				pin.Value = int(p.contrast * 100)
 			}
 		default:
diff --git a/revid/audio_OSX.go b/revid/audio_darwin.go
similarity index 97%
rename from revid/audio_OSX.go
rename to revid/audio_darwin.go
index b31e3e47..c7f99a23 100644
--- a/revid/audio_OSX.go
+++ b/revid/audio_darwin.go
@@ -1,6 +1,6 @@
 /*
 NAME
-  audio_OSX.go
+  audio_darwin.go
 
 AUTHORS
   Russell Stanley <russell@ausocean.org>