DVD VOB 14-Byte Pack Header Structure

This article provides a technical reference for the exact 14-byte pack header structure used in DVD Video Object (VOB) files. Because DVD-Video relies on the MPEG-2 Program Stream (ISO/IEC 13818-1) standard, every 2048-byte sector in a VOB file begins with this fixed 14-byte pack header containing synchronization, timing, and multiplexing data.

Byte-by-Byte Layout Overview

Byte Offset	Field Description	Size	Expected Values / Mask
0 – 3	Pack Start Code	32 bits	`0x000001BA`
4 – 9	System Clock Reference (SCR) & Marker Bits	48 bits	MPEG-2 SCR format (`01b` prefix)
10 – 12	Program Multiplex Rate & Marker Bits	24 bits	DVD max rate `10.08 Mbps` (`0x0189C1`)
13	Reserved Bits & Pack Stuffing Length	8 bits	`0xF8` (0 stuffing bytes)

Detailed Bit-Level Breakdown

Bytes 0–3: Pack Start Code

Length: 32 bits
Value: 0x00, 0x00, 0x01, 0xBA
Identifies the beginning of an MPEG-2 Program Stream pack.

Bytes 4–9: System Clock Reference (SCR)

The SCR is a 42-bit value consisting of a 33-bit base clock (at 90 kHz) and a 9-bit extension (at 27 MHz), interleaved with marker bits to prevent start-code emulation.

Byte 4:
- Bits 7–6: Identifier 01 (denotes MPEG-2, unlike MPEG-1 which uses 0010)
- Bits 5–3: SCR_base[32..30]
- Bit 2: Marker bit (always 1)
- Bits 1–0: SCR_base[29..28]
Byte 5:
- Bits 7–0: SCR_base[27..20]
Byte 6:
- Bits 7–3: SCR_base[19..15]
- Bit 2: Marker bit (always 1)
- Bits 1–0: SCR_base[14..13]
Byte 7:
- Bits 7–0: SCR_base[12..5]
Byte 8:
- Bits 7–3: SCR_base[4..0]
- Bit 2: Marker bit (always 1)
- Bits 1–0: SCR_extension[8..7]
Byte 9:
- Bits 7–1: SCR_extension[6..0]
- Bit 0: Marker bit (always 1)

Bytes 10–12: Program Multiplex Rate

Specifies the maximum rate at which the Program Stream is transmitted, measured in units of 50 bytes per second.

Byte 10:
- Bits 7–0: program_mux_rate[21..14]
Byte 11:
- Bits 7–0: program_mux_rate[13..6]
Byte 12:
- Bits 7–2: program_mux_rate[5..0]
- Bits 1–0: Marker bits (always 11)

Note: For DVD-Video, this value is fixed at 10.08 Mbps (25,200 units of 50 bytes/s), yielding the 22-bit integer 100800 (0x0189C0). When combined with the two trailing 11 marker bits, Byte 10 to Byte 12 standardly reads as 0x01 0x89 0xC1.

Byte 13: Pack Stuffing Length

Bits 7–3: Reserved bits (always 11111)
Bits 2–0: pack_stuffing_length (3 bits)
- Indicates the number of optional stuffing bytes immediately following this byte.
- In standard DVD VOB sectors, stuffing is handled inside the PES packets instead of the pack header, setting this value to 000.
- As a result, Byte 13 evaluates to 0xF8 (11111000 in binary), terminating the pack header at exactly 14 bytes.