diff --git a/.golangci.yml b/.golangci.yml
index e10b982..1911cbf 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -67,6 +67,9 @@ linters:
       disable:
       - fieldalignment
       - reflectvaluecompare
+      settings:
+        shadow:
+          strict: true
 
 formatters:
   enable:
diff --git a/pkg/codecs/av1/sequence_header.go b/pkg/codecs/av1/sequence_header.go
index eccf91e..54129f2 100644
--- a/pkg/codecs/av1/sequence_header.go
+++ b/pkg/codecs/av1/sequence_header.go
@@ -175,7 +175,8 @@ func (c *SequenceHeader_ColorConfig) unmarshal(seqProfile uint8, buf []byte, pos
 		}
 
 		if c.SubsamplingX && c.SubsamplingY {
-			tmp, err := bits.ReadBits(buf, pos, 2)
+			var tmp uint64
+			tmp, err = bits.ReadBits(buf, pos, 2)
 			if err != nil {
 				return err
 			}
diff --git a/pkg/codecs/h264/sps.go b/pkg/codecs/h264/sps.go
index e6a9983..69940ef 100644
--- a/pkg/codecs/h264/sps.go
+++ b/pkg/codecs/h264/sps.go
@@ -357,7 +357,7 @@ func (v *SPS_VUI) unmarshal(buf []byte, pos *int) error {
 
 	if bitstreamRestrictionFlag {
 		v.BitstreamRestriction = &SPS_BitstreamRestriction{}
-		err := v.BitstreamRestriction.unmarshal(buf, pos)
+		err = v.BitstreamRestriction.unmarshal(buf, pos)
 		if err != nil {
 			return err
 		}
@@ -706,7 +706,7 @@ func (s *SPS) Unmarshal(buf []byte) error {
 
 	if vuiParametersPresentFlag {
 		s.VUI = &SPS_VUI{}
-		err := s.VUI.unmarshal(buf, &pos)
+		err = s.VUI.unmarshal(buf, &pos)
 		if err != nil {
 			return err
 		}
diff --git a/pkg/codecs/h265/dts_extractor.go b/pkg/codecs/h265/dts_extractor.go
index 0632141..f7a689b 100644
--- a/pkg/codecs/h265/dts_extractor.go
+++ b/pkg/codecs/h265/dts_extractor.go
@@ -98,7 +98,8 @@ func getPTSDTSDiff(buf []byte, sps *SPS, pps *PPS) (uint32, error) {
 		}
 
 		b := int(math.Ceil(math.Log2(float64(len(sps.ShortTermRefPicSets)))))
-		tmp, err := bits.ReadBits(buf, &pos, b)
+		var tmp uint64
+		tmp, err = bits.ReadBits(buf, &pos, b)
 		if err != nil {
 			return 0, err
 		}
diff --git a/pkg/codecs/h265/sps.go b/pkg/codecs/h265/sps.go
index 82f695b..ebe2dc5 100644
--- a/pkg/codecs/h265/sps.go
+++ b/pkg/codecs/h265/sps.go
@@ -298,7 +298,7 @@ func (v *SPS_VUI) unmarshal(buf []byte, pos *int) error {
 
 	if timingInfoPresentFlag {
 		v.TimingInfo = &SPS_TimingInfo{}
-		err := v.TimingInfo.unmarshal(buf, pos)
+		err = v.TimingInfo.unmarshal(buf, pos)
 		if err != nil {
 			return err
 		}
@@ -382,7 +382,7 @@ func (p *SPS_ProfileTierLevel) unmarshal(buf []byte, pos *int, maxSubLayersMinus
 		p.SubLayerProfilePresentFlag = make([]bool, maxSubLayersMinus1)
 		p.SubLayerLevelPresentFlag = make([]bool, maxSubLayersMinus1)
 
-		err := bits.HasSpace(buf, *pos, int(2*maxSubLayersMinus1))
+		err = bits.HasSpace(buf, *pos, int(2*maxSubLayersMinus1))
 		if err != nil {
 			return err
 		}
@@ -394,7 +394,7 @@ func (p *SPS_ProfileTierLevel) unmarshal(buf []byte, pos *int, maxSubLayersMinus
 	}
 
 	if maxSubLayersMinus1 > 0 {
-		err := bits.HasSpace(buf, *pos, int(8-maxSubLayersMinus1)*2)
+		err = bits.HasSpace(buf, *pos, int(8-maxSubLayersMinus1)*2)
 		if err != nil {
 			return err
 		}
@@ -568,7 +568,8 @@ func (r *SPS_ShortTermRefPicSet) unmarshal(buf []byte, pos *int, stRpsIdx uint32
 			r.UsedByCurrPicS0Flag = make([]bool, r.NumNegativePics)
 
 			for i := uint32(0); i < r.NumNegativePics; i++ {
-				deltaPocS0Minus1, err := bits.ReadGolombUnsigned(buf, pos)
+				var deltaPocS0Minus1 uint32
+				deltaPocS0Minus1, err = bits.ReadGolombUnsigned(buf, pos)
 				if err != nil {
 					return err
 				}
@@ -595,7 +596,8 @@ func (r *SPS_ShortTermRefPicSet) unmarshal(buf []byte, pos *int, stRpsIdx uint32
 			r.UsedByCurrPicS1Flag = make([]bool, r.NumPositivePics)
 
 			for i := uint32(0); i < r.NumPositivePics; i++ {
-				deltaPocS1Minus1, err := bits.ReadGolombUnsigned(buf, pos)
+				var deltaPocS1Minus1 uint32
+				deltaPocS1Minus1, err = bits.ReadGolombUnsigned(buf, pos)
 				if err != nil {
 					return err
 				}
@@ -934,7 +936,7 @@ func (s *SPS) Unmarshal(buf []byte) error {
 
 	if vuiParametersPresentFlag {
 		s.VUI = &SPS_VUI{}
-		err := s.VUI.unmarshal(buf, &pos)
+		err = s.VUI.unmarshal(buf, &pos)
 		if err != nil {
 			return err
 		}
diff --git a/pkg/codecs/mpeg4audio/audio_specific_config.go b/pkg/codecs/mpeg4audio/audio_specific_config.go
index 8c108e8..e4e1e6c 100644
--- a/pkg/codecs/mpeg4audio/audio_specific_config.go
+++ b/pkg/codecs/mpeg4audio/audio_specific_config.go
@@ -177,7 +177,7 @@ func (c AudioSpecificConfig) marshalSizeBits() int {
 	}
 
 	if c.ExtensionType == ObjectTypeSBR || c.ExtensionType == ObjectTypePS {
-		_, ok := reverseSampleRates[c.ExtensionSampleRate]
+		_, ok = reverseSampleRates[c.ExtensionSampleRate]
 		if !ok {
 			n += 28
 		} else {
@@ -246,7 +246,7 @@ func (c AudioSpecificConfig) marshalToBits(buf []byte, pos *int) error {
 	bits.WriteBitsUnsafe(buf, pos, uint64(channelConfig), 4)
 
 	if c.ExtensionType == ObjectTypeSBR || c.ExtensionType == ObjectTypePS {
-		sampleRateIndex, ok := reverseSampleRates[c.ExtensionSampleRate]
+		sampleRateIndex, ok = reverseSampleRates[c.ExtensionSampleRate]
 		if !ok {
 			bits.WriteBitsUnsafe(buf, pos, uint64(0x0F), 4)
 			bits.WriteBitsUnsafe(buf, pos, uint64(c.ExtensionSampleRate), 24)
diff --git a/pkg/codecs/mpeg4audio/payload_mux.go b/pkg/codecs/mpeg4audio/payload_mux.go
index c61ce3b..99414e8 100644
--- a/pkg/codecs/mpeg4audio/payload_mux.go
+++ b/pkg/codecs/mpeg4audio/payload_mux.go
@@ -29,7 +29,8 @@ func (m *payloadMux) unmarshalBits(buf []byte, pos *int, li *payloadLengthInfo)
 			payload := make([]byte, payloadLength)
 
 			for i := range payloadLength {
-				byt, err := bits.ReadBits(buf, pos, 8)
+				var byt uint64
+				byt, err = bits.ReadBits(buf, pos, 8)
 				if err != nil {
 					return err
 				}
diff --git a/pkg/codecs/mpeg4audio/stream_mux_config.go b/pkg/codecs/mpeg4audio/stream_mux_config.go
index 9195eb9..6362170 100644
--- a/pkg/codecs/mpeg4audio/stream_mux_config.go
+++ b/pkg/codecs/mpeg4audio/stream_mux_config.go
@@ -181,7 +181,8 @@ func (c *StreamMuxConfig) unmarshalBits(buf []byte, pos *int) error {
 	}
 
 	if c.CRCCheckPresent {
-		tmp, err := bits.ReadBits(buf, pos, 8)
+		var tmp uint64
+		tmp, err = bits.ReadBits(buf, pos, 8)
 		if err != nil {
 			return err
 		}
diff --git a/pkg/codecs/vp9/header.go b/pkg/codecs/vp9/header.go
index 171f3a2..c483792 100644
--- a/pkg/codecs/vp9/header.go
+++ b/pkg/codecs/vp9/header.go
@@ -40,14 +40,13 @@ func (c *Header_ColorConfig) unmarshal(profile uint8, buf []byte, pos *int) erro
 	c.ColorSpace = uint8(tmp)
 
 	if c.ColorSpace != 7 {
-		var err error
 		c.ColorRange, err = bits.ReadFlag(buf, pos)
 		if err != nil {
 			return err
 		}
 
 		if profile == 1 || profile == 3 {
-			err := bits.HasSpace(buf, *pos, 3)
+			err = bits.HasSpace(buf, *pos, 3)
 			if err != nil {
 				return err
 			}
@@ -66,7 +65,7 @@ func (c *Header_ColorConfig) unmarshal(profile uint8, buf []byte, pos *int) erro
 			c.SubsamplingX = false
 			c.SubsamplingY = false
 
-			err := bits.HasSpace(buf, *pos, 1)
+			err = bits.HasSpace(buf, *pos, 1)
 			if err != nil {
 				return err
 			}
@@ -158,7 +157,7 @@ func (h *Header) Unmarshal(buf []byte) error {
 	h.ErrorResilientMode = bits.ReadFlagUnsafe(buf, &pos)
 
 	if !h.NonKeyFrame {
-		err := bits.HasSpace(buf, pos, 24)
+		err = bits.HasSpace(buf, pos, 24)
 		if err != nil {
 			return err
 		}
diff --git a/pkg/formats/fmp4/init.go b/pkg/formats/fmp4/init.go
index c578b8c..65a36c3 100644
--- a/pkg/formats/fmp4/init.go
+++ b/pkg/formats/fmp4/init.go
@@ -23,7 +23,7 @@ func av1FindSequenceHeader(buf []byte) ([]byte, error) {
 
 	for _, obu := range tu {
 		var h av1.OBUHeader
-		err := h.Unmarshal(obu)
+		err = h.Unmarshal(obu)
 		if err != nil {
 			return nil, err
 		}
@@ -472,7 +472,7 @@ func (i *Init) Unmarshal(r io.ReadSeeker) error {
 						}
 
 						var c mpeg4audio.AudioSpecificConfig
-						err := c.Unmarshal(spec)
+						err = c.Unmarshal(spec)
 						if err != nil {
 							return nil, fmt.Errorf("invalid MPEG-4 Audio configuration: %w", err)
 						}
diff --git a/pkg/formats/mpegts/opus_control_header.go b/pkg/formats/mpegts/opus_control_header.go
index ca81387..5425f9b 100644
--- a/pkg/formats/mpegts/opus_control_header.go
+++ b/pkg/formats/mpegts/opus_control_header.go
@@ -73,7 +73,7 @@ func (h *opusControlHeader) unmarshal(buf []byte) (int, error) {
 	}
 
 	if h.StartTrimFlag {
-		err := bits.HasSpace(buf, pos, 16)
+		err = bits.HasSpace(buf, pos, 16)
 		if err != nil {
 			return 0, err
 		}
@@ -83,7 +83,7 @@ func (h *opusControlHeader) unmarshal(buf []byte) (int, error) {
 	}
 
 	if h.EndTrimFlag {
-		err := bits.HasSpace(buf, pos, 16)
+		err = bits.HasSpace(buf, pos, 16)
 		if err != nil {
 			return 0, err
 		}
@@ -93,7 +93,8 @@ func (h *opusControlHeader) unmarshal(buf []byte) (int, error) {
 	}
 
 	if h.ControlExtensionFlag {
-		tmp, err := bits.ReadBits(buf, &pos, 8)
+		var tmp uint64
+		tmp, err = bits.ReadBits(buf, &pos, 8)
 		if err != nil {
 			return 0, err
 		}
diff --git a/pkg/formats/mpegts/reader.go b/pkg/formats/mpegts/reader.go
index 8a49c20..0be5583 100644
--- a/pkg/formats/mpegts/reader.go
+++ b/pkg/formats/mpegts/reader.go
@@ -87,8 +87,8 @@ func readMetadataAUWrapper(in []byte) ([]byte, error) {
 	out := au.AUCellData
 
 	for {
-		var au metadataAUCell
-		n2, err := au.unmarshal(in[n:])
+		var n2 int
+		n2, err = au.unmarshal(in[n:])
 		if err != nil {
 			return nil, err
 		}
@@ -197,7 +197,7 @@ func (r *Reader) Initialize() error {
 
 	for i, es := range pmt.ElementaryStreams {
 		var track Track
-		err := track.unmarshal(dem, es)
+		err = track.unmarshal(dem, es)
 		if err != nil {
 			return err
 		}
diff --git a/pkg/formats/mpegts/reader_test.go b/pkg/formats/mpegts/reader_test.go
index 385f60e..ad949b3 100644
--- a/pkg/formats/mpegts/reader_test.go
+++ b/pkg/formats/mpegts/reader_test.go
@@ -1087,7 +1087,7 @@ func TestReader(t *testing.T) {
 			}
 
 			for {
-				err := r.Read()
+				err = r.Read()
 				if errors.Is(err, io.EOF) {
 					break
 				}
@@ -1214,7 +1214,7 @@ func TestReaderKLVAsync(t *testing.T) {
 	})
 
 	for {
-		err := r.Read()
+		err = r.Read()
 		if errors.Is(err, io.EOF) {
 			break
 		}
@@ -1525,7 +1525,7 @@ func TestReaderDecodeErrors(t *testing.T) {
 			})
 
 			for {
-				err := r.Read()
+				err = r.Read()
 				if err != nil {
 					require.ErrorIs(t, io.EOF, err)
 					break
@@ -1684,7 +1684,7 @@ func TestReaderSkipGarbage(t *testing.T) {
 	})
 
 	for {
-		err := r.Read()
+		err = r.Read()
 		if err != nil {
 			require.ErrorIs(t, io.EOF, err)
 			break
diff --git a/pkg/formats/mpegts/time_decoder_test.go b/pkg/formats/mpegts/time_decoder_test.go
index 8676a39..a7688d6 100644
--- a/pkg/formats/mpegts/time_decoder_test.go
+++ b/pkg/formats/mpegts/time_decoder_test.go
@@ -40,7 +40,7 @@ func TestTimeDecoderOverflow(t *testing.T) {
 		// overflow
 		i += 90000 * stride
 		secs += stride
-		ts := d.Decode(i)
+		ts = d.Decode(i)
 		require.Equal(t, secs*90000, ts)
 
 		// reach 2^32 slowly
diff --git a/pkg/formats/mpegts/writer_test.go b/pkg/formats/mpegts/writer_test.go
index 36562d2..e9b2104 100644
--- a/pkg/formats/mpegts/writer_test.go
+++ b/pkg/formats/mpegts/writer_test.go
@@ -116,7 +116,8 @@ func TestWriterKLVAsync(t *testing.T) {
 
 	var pkts []*astits.Packet
 	for {
-		pkt, err := dem.NextPacket()
+		var pkt *astits.Packet
+		pkt, err = dem.NextPacket()
 		if errors.Is(err, astits.ErrNoMorePackets) {
 			break
 		}
@@ -240,7 +241,7 @@ func TestWriterReaderLongKLVSync(t *testing.T) {
 	})
 
 	for {
-		err := r.Read()
+		err = r.Read()
 		if errors.Is(err, io.EOF) {
 			break
 		}
diff --git a/pkg/formats/pmp4/presentation.go b/pkg/formats/pmp4/presentation.go
index e1bf464..e08d89b 100644
--- a/pkg/formats/pmp4/presentation.go
+++ b/pkg/formats/pmp4/presentation.go
@@ -32,7 +32,7 @@ func av1FindSequenceHeader(buf []byte) ([]byte, error) {
 
 	for _, obu := range tu {
 		var h av1.OBUHeader
-		err := h.Unmarshal(obu)
+		err = h.Unmarshal(obu)
 		if err != nil {
 			return nil, err
 		}
@@ -524,7 +524,7 @@ func (p *Presentation) Unmarshal(r io.ReadSeeker) error {
 					}
 
 					var c mpeg4audio.AudioSpecificConfig
-					err := c.Unmarshal(spec)
+					err = c.Unmarshal(spec)
 					if err != nil {
 						return nil, fmt.Errorf("invalid MPEG-4 Audio configuration: %w", err)
 					}
@@ -808,14 +808,14 @@ func (p *Presentation) Unmarshal(r io.ReadSeeker) error {
 					curTrack.Samples[i].PayloadSize = sampleSize
 
 					curTrack.Samples[i].GetPayload = func() ([]byte, error) {
-						_, err = r.Seek(int64(sampleOffset), io.SeekStart)
+						_, err2 := r.Seek(int64(sampleOffset), io.SeekStart)
 						if err != nil {
-							return nil, err
+							return nil, err2
 						}
 
 						buf := make([]byte, sampleSize)
-						_, err = io.ReadFull(r, buf)
-						return buf, err
+						_, err2 = io.ReadFull(r, buf)
+						return buf, err2
 					}
 
 					off += sampleSize
@@ -1021,7 +1021,8 @@ func (p *Presentation) marshalMdat(w io.Writer, dataSize uint32, sortedSamples [
 	}
 
 	for _, sa := range sortedSamples {
-		pl, err := sa.GetPayload()
+		var pl []byte
+		pl, err = sa.GetPayload()
 		if err != nil {
 			return err
 		}