Standard VOB Container Pack Byte Size

This article examines the fixed byte size of individual packs within standard DVD Video Object (VOB) containers. It provides the exact numerical byte measurement, explains the technical standard governing this structure, details the internal breakdown of a pack, and explains why this specific sizing is critical for DVD media compatibility.

The fixed byte size of an individual pack within a standard VOB container is exactly 2,048 bytes (2 kilobytes).

A VOB file is built upon the MPEG-2 Program Stream (MPEG-2 PS) specification, defined by ISO/IEC 13818-1. While generic MPEG-2 Program Streams permit variable pack lengths, the DVD-Video specification (DVD Forum) strictly enforces a fixed size of 2,048 bytes per pack.

This 2,048-byte requirement directly mirrors the physical architecture of DVD-ROM media. Standard DVD sectors contain precisely 2,048 bytes of usable data area. By fixing the VOB pack size to match the physical sector size exactly, DVD players can read, buffer, and stream data using a direct 1:1 mapping between disc sectors and multiplexed stream packs, eliminating the overhead required for complex re-framing.

Every 2,048-byte VOB pack consists of a sequence of structured elements:

• Pack Header (14 bytes): Begins with the standard Pack Start Code (0x000001BA), followed by the System Clock Reference (SCR) and the program multiplex rate.
• System Header (optional, variable size): Present only in certain packs, such as the initial pack of a stream or immediately following a navigation pack.
• Payload (variable size): Consists of Packetized Elementary Stream (PES) packets containing video (MPEG-2 or MPEG-1), audio (AC-3, DTS, or LPCM), sub-pictures, or DVD-specific private data streams like Navigation Packs (NV_PCK).
• Padding/Stuffing Bytes: If the active payload and headers do not fill the allocation, stuffing bytes are automatically appended to ensure the final pack length reaches exactly 2,048 bytes.