audio: style and doc

input/audio/audio.go

@@ -252,17 +252,19 @@ func (d *Device) open() error {
 	// Eg. the audioinjector sound card is supposed to record at 8000Hz and 16000Hz but it can't due to a firmware issue,
 	// a fix for this is to remove 8000 and 16000 from the rates slice.
 	var rates = [8]int{8000, 16000, 32000, 44100, 48000, 88200, 96000, 192000}
-	foundRate := false
+
 	var rate int
-	for i := 0; i < len(rates) && !foundRate; i++ {
-		if rates[i] < d.SampleRate {
+	foundRate := false
+	for r := range rates {
+		if r < d.SampleRate {
 			continue
 		}
-		if rates[i]%d.SampleRate == 0 {
-			rate, err = d.dev.NegotiateRate(rates[i])
+		if r%d.SampleRate == 0 {
+			rate, err = d.dev.NegotiateRate(r)
 			if err == nil {
 				foundRate = true
 				d.l.Log(logger.Debug, pkg+"alsa device sample rate set", "rate", rate)
+				break
 			}
 		}
 	}
@@ -385,11 +387,7 @@ func (d *Device) Read(p []byte) (int, error) {
 	}
 
 	// Read from ring buffer.
-	n, err := d.rb.Read(p)
-	if err != nil {
-		return 0, err
-	}
-	return n, nil
+	return d.rb.Read(p)
 }
 
 // formatBuffer returns audio that has been converted to the desired format.
@@ -440,6 +438,7 @@ func (d *Device) formatBuffer() alsa.Buffer {
 // nearestPowerOfTwo finds and returns the nearest power of two to the given integer.
 // If the lower and higher power of two are the same distance, it returns the higher power.
 // For negative values, 1 is returned.
+// Source: https://stackoverflow.com/a/45859570
 func nearestPowerOfTwo(n int) int {
 	if n <= 0 {
 		return 1

revid/revid.go

@@ -626,6 +626,7 @@ func (r *Revid) setupInputForFile() (func() error, error) {
 }
 
 // startAudioDevice is used to start capturing audio from an audio device and processing it.
+// It returns a function that can be used to stop the device and any errors that occur.
 func (r *Revid) startAudioDevice() (func() error, error) {
 	// Create audio device.
 	ac := &audio.Config{

revid/revid_test.go

@@ -41,7 +41,7 @@ import (
 const raspividPath = "/usr/local/bin/raspivid"
 
 // Suppress all test logging, except for t.Errorf output.
-var silent bool = true
+var silent = true
 
 // TestRaspivid tests that raspivid starts correctly.
 // It is intended to be run on a Raspberry Pi.