.MOV File Format – Data types and codes

Numbers and dates

Matrices

A display matrix is 36 bytes: nine values stored in the order a, b, u, c, d, v, x, y, w. All are 16.16 fixed except u, v and w, which are 2.30. A point (x, y) maps to (a·x + c·y + x_t, b·x + d·y + y_t), where x_t and y_t are the stored x and y; u and v are normally 0 and w is 1.0. The movie matrix in mvhd applies to everything in the movie, on top of each track’s matrix.

With w = 0x40000000. For a rotation, x and y also carry the translation that moves the picture back into view (the track height or width, in 16.16).

Balance

An 8.8 fixed value from −1.0 (left) to +1.0 (right); 0 is centred.

Graphics modes

How a track or image is combined with what lies behind it, from QuickDraw’s transfer modes. Some use the opcolor.

Language codes

A 16-bit language field holds either a Macintosh language code (below 0x400, or 0x7FFF for unspecified), whose text is in a Macintosh encoding, or a packed ISO 639-2/T code (0x400 and up), whose text is Unicode. Apple allows ISO codes only for user data text; other fields, including text tracks, are meant to use Macintosh codes, though mdhd in most current files holds a packed ISO code.

Packed ISO 639-2/T

Subtract 0x60 from each of the three lower-case letters and pack the 5-bit results into bits 14–10, 9–5 and 4–0; bit 15 is 0. For jpn: j 0x6A → 0x0A, p 0x70 → 0x10, n 0x6E → 0x0E, giving 0x0A × 0x400 + 0x10 × 0x20 + 0x0E = 0x2A0E. eng packs to 0x15C7 (5575) and und to 0x55C4.

Macintosh language codes

Apple’s list has no code 86 and nothing between 95 and 127.

Registered QuickTime sample entries

The 59 sample description formats the MP4 Registration Authority lists for QuickTime, with their media. Codes with a trailing space are shown with a gap. The formats Apple’s own pages list are on Video and Sound sample descriptions; ISO family codes such as avc1, hvc1 and mp4a are on the MP4 Sample entries page.

Apple’s video list writes Cinepak as cvid, the code found in files; the registry lists civd.

Registered QuickTime atoms

Registered QuickTime track references: cdep structural dependency, chap chapter list, scpt transcript, ssrc non-primary source and tmcd timecode (see Track references).

Registered user data items

User data items registered with the MP4 Registration Authority, in addition to Apple’s own list on Movie atoms. Many come from 3GPP (see the 3GP pages) and ISO.

The registry gives names only, not layouts. The 3GPP items are laid out on the 3GP pages; the layouts of the Apple camera items (angl to slno) are not covered here.