Improve SPS parser

pkg/h264/h264_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/hex"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -83,3 +84,12 @@ func TestGetProfileLevelID(t *testing.T) {
 	profile = GetProfileLevelID(s)
 	require.Equal(t, "640029", profile)
 }
+
+func TestDecodeSPS2(t *testing.T) {
+	s := "6764001fad84010c20086100430802184010c200843b50740932"
+	b, err := hex.DecodeString(s)
+	require.Nil(t, err)
+
+	sps := DecodeSPS(b)
+	assert.Nil(t, sps) // broken SPS?
+}

pkg/h264/sps.go

@@ -115,9 +115,14 @@ func DecodeSPS(sps []byte) *SPS {
 		s.seq_scaling_matrix_present_flag = r.ReadBit()
 		if s.seq_scaling_matrix_present_flag != 0 {
 			for i := byte(0); i < n; i++ {
-				ssl := r.ReadBit() // seq_scaling_list_present_flag[i]
+				//goland:noinspection GoSnakeCaseUsage
-				if ssl != 0 {
+				seq_scaling_list_present_flag := r.ReadBit()
-					return nil // not implemented
+				if seq_scaling_list_present_flag != 0 {
+					if i < 6 {
+						s.scaling_list(r, 16)
+					} else {
+						s.scaling_list(r, 64)
+					}
 				}
 			}
 		}
@@ -209,3 +214,18 @@ func DecodeSPS(sps []byte) *SPS {
 
 	return s
 }
+
+//goland:noinspection GoSnakeCaseUsage
+func (s *SPS) scaling_list(r *bits.Reader, sizeOfScalingList int) {
+	lastScale := int32(8)
+	nextScale := int32(8)
+	for j := 0; j < sizeOfScalingList; j++ {
+		if nextScale != 0 {
+			delta_scale := r.ReadSEGolomb()
+			nextScale = (lastScale + delta_scale + 256) % 256
+		}
+		if nextScale != 0 {
+			lastScale = nextScale
+		}
+	}
+}