if disc only 1 will not add disc number

main.go

@@ -812,18 +812,19 @@ func writeM4a(w *mp4.Writer, info *SongInfo, meta *AutoGenerated, data []byte, t
 					}
 
 					trkn := make([]byte, 8)
-					binary.BigEndian.PutUint32(trkn, uint32(trackNum))
+					binary.BigEndian.PutUint32(trkn, uint32(meta.Data[0].Relationships.Tracks.Data[index].Attributes.TrackNumber))
 					binary.BigEndian.PutUint16(trkn[4:], uint16(trackTotal))
 					err = addMeta(mp4.BoxType{'t', 'r', 'k', 'n'}, trkn)
 					if err != nil {
 						return err
 					}
-
-					disk := make([]byte, 8)
-					binary.BigEndian.PutUint32(disk, uint32(meta.Data[0].Relationships.Tracks.Data[index].Attributes.DiscNumber))
-					err = addMeta(mp4.BoxType{'d', 'i', 's', 'k'}, disk)
-					if err != nil {
-						return err
+					if meta.Data[0].Relationships.Tracks.Data[trackTotal - 1].Attributes.DiscNumber > 1{
+						disk := make([]byte, 8)
+						binary.BigEndian.PutUint32(disk, uint32(meta.Data[0].Relationships.Tracks.Data[index].Attributes.DiscNumber))
+						err = addMeta(mp4.BoxType{'d', 'i', 's', 'k'}, disk)
+						if err != nil {
+							return err
+						}
 					}
 
 					ctx.UnderIlst = false
@@ -2055,4 +2056,4 @@ type SongLyrics struct {
 			} `json:"playParams"`
 		} `json:"attributes"`
 	} `json:"data"`
-}
+}