Except as provided in § 19.2-400 for pretrial appeals by the Commonwealth in criminal cases and in § 19.2-401 for cross appeals by the defendant in such pretrial appeals, a notice of appeal to the Court of Appeals in any case within the jurisdiction of the court shall be filed within 30 days from the date of any final judgment order, decree, or conviction. When an appeal from an interlocutory decree or order is permitted, the notice of appeal shall be filed within 30 days from the date of such decree or order, except for pretrial appeals pursuant to § 19.2-398. However, an extension may be granted, in the discretion of the Court of Appeals, on motion for good cause shown. For purposes of this section, § 17.1-408, and an appeal pursuant to § 19.2-398, a petition for appeal in a criminal case or a notice of appeal to the Court of Appeals, shall be deemed to be timely filed if (i) it is mailed postage prepaid by registered or certified mail and (ii) the official postal receipt, showing mailing within the prescribed time limits, is exhibited upon demand of the clerk or any party.