diff --git a/codec/mjpeg/extract.go b/codec/mjpeg/extract.go
index d0f2e791..4181639c 100644
--- a/codec/mjpeg/extract.go
+++ b/codec/mjpeg/extract.go
@@ -74,7 +74,11 @@ type Extractor struct {
 }
 
 // NewExtractor returns a new Extractor.
-func NewExtractor() *Extractor { return &Extractor{} }
+func NewExtractor() *Extractor {
+	return &Extractor{
+		buf: new(bytes.Buffer),
+	}
+}
 
 // Extract will continously read RTP packets from src containing JPEG (in RTP
 // payload format) and extract the JPEG images, sending them to dst. This
@@ -248,7 +252,7 @@ func (b *byteStream) remaining() int {
 }
 
 func (b *byteStream) writeTo(w io.Writer, n int) error {
-	_n,err := w.Write(b.bytes[b.i:n])
+	_n,err := w.Write(b.bytes[b.i:b.i+n])
 	b.i += _n
 	if err != nil {
 		return err
diff --git a/codec/mjpeg/jpeg.go b/codec/mjpeg/jpeg.go
index 72daf6f6..fd44a623 100644
--- a/codec/mjpeg/jpeg.go
+++ b/codec/mjpeg/jpeg.go
@@ -25,6 +25,7 @@ LICENSE
 package mjpeg
 
 import (
+	"bytes"
 	"encoding/binary"
 	"fmt"
 	"io"
@@ -35,7 +36,7 @@ const (
 	codeSOI  = 0xd8 // Start of image.
 	codeDRI  = 0xdd // Define restart interval.
 	codeDQT  = 0xdb // Define quantization tables.
-	codeDHT  = 0xde // Define hierarchical progression.
+	codeDHT  = 0xc4 // Define huffman tables.
 	codeSOS  = 0xda // Start of scan.
 	codeAPP0 = 0xe0 // TODO: find out what this is.
 	codeSOF0 = 0xc0 // Baseline
@@ -165,7 +166,7 @@ func writeHeader(w io.Writer, _type, width, height, nbqTab, dri int, qtable []by
 			return fmt.Errorf("could not write DRI marker code: %w", err)
 		}
 
-		_, err := w.Write([]byte{0x00, 0x04, byte(dri >> 4), byte(dri)})
+		_, err := w.Write([]byte{0x00, 0x04, byte(dri >> 8), byte(dri)})
 		if err != nil {
 			return fmt.Errorf("could not write restart interval value: %w", err)
 		}
@@ -179,7 +180,7 @@ func writeHeader(w io.Writer, _type, width, height, nbqTab, dri int, qtable []by
 
 	// Calculate table size and create slice for table.
 	ts := 2 + nbqTab*(1+64)
-	_, err = w.Write([]byte{byte(ts >> 4), byte(ts)})
+	_, err = w.Write([]byte{byte(ts >> 8), byte(ts)})
 	if err != nil {
 		return fmt.Errorf("could not write quantization table size: %w", err)
 	}
@@ -203,14 +204,25 @@ func writeHeader(w io.Writer, _type, width, height, nbqTab, dri int, qtable []by
 	}
 
 	var me multiError
-	me.add(writeHuffman(w, 0, 0, bitsDCLum, valDC))
-	me.add(writeHuffman(w, 0, 1, bitsDCChr, valDC))
-	me.add(writeHuffman(w, 1, 0, bitsACLum, valACLum))
-	me.add(writeHuffman(w, 1, 1, bitsACChr, valACChr))
+	buf := new(bytes.Buffer)
+	me.add(writeHuffman(buf, 0, 0, bitsDCLum, valDC))
+	me.add(writeHuffman(buf, 0, 1, bitsDCChr, valDC))
+	me.add(writeHuffman(buf, 1, 0, bitsACLum, valACLum))
+	me.add(writeHuffman(buf, 1, 1, bitsACChr, valACChr))
 	if me != nil {
 		return fmt.Errorf("error writing huffman tables: %w", err)
 	}
-	return nil
+
+	l := buf.Len() + 2
+	_, err = w.Write([]byte{byte(l >> 8), byte(l)})
+	if err != nil {
+		return fmt.Errorf("could not write quantization table entry: %w", err)
+	}
+
+	_, err = buf.WriteTo(w)
+	if err != nil {
+		return fmt.Errorf("could not write huffman tables: %w", err)
+	}
 
 	// Start of frame.
 	err = writeMarker(w, codeSOF0)
diff --git a/device/geovision/geovision.go b/device/geovision/geovision.go
index 1b3e82ef..d09054ad 100644
--- a/device/geovision/geovision.go
+++ b/device/geovision/geovision.go
@@ -68,7 +68,7 @@ const (
 	defaultFrameRate  = 25
 	defaultBitrate    = 400
 	defaultVBRBitrate = 400
-	defaultMinFrames  = 100
+	defaultMinFrames  = 3
 	defaultVBRQuality = avconfig.QualityStandard
 	defaultCameraChan = 2
 )
@@ -136,9 +136,10 @@ func (g *GeoVision) Set(c avconfig.Config) error {
 		c.Bitrate = defaultBitrate
 	}
 
-	if c.MinFrames <= 0 {
+	refresh := float64(c.MinFrames) / float64(c.FrameRate)
+	if refresh < 1 || refresh > 5 {
 		errs = append(errs, errGVBadMinFrames)
-		c.MinFrames = defaultMinFrames
+		c.MinFrames = 4 * c.FrameRate
 	}
 
 	// If we're using RTMP then we should default to constant bitrate.
diff --git a/revid/revid.go b/revid/revid.go
index b2b399dc..44ea3108 100644
--- a/revid/revid.go
+++ b/revid/revid.go
@@ -362,7 +362,7 @@ func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.
 		case codecutil.H265:
 			r.lexTo = h265.NewLexer(false).Lex
 		case codecutil.MJPEG:
-			panic("not implemented")
+			r.lexTo = mjpeg.NewExtractor().Extract
 		}
 
 	case config.InputAudio: