Longitudinal Timecode Data Format
The basic format is an 80-bit code that gives the time of day to the second, and the frame number within the second. Values are stored in binary-coded decimal, least significant bit first. There are thirty-two bits of user data, usually used for a reel number and date.
| Bit | Weight | Meaning | Bit | Weight | Meaning | Bit | Weight | Meaning | Bit | Weight | Meaning | Bit | Value | Meaning | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 00 | 1 | Frame number units (0–23, 24, or 29) |
16 | 1 | Seconds units (0–59) |
32 | 1 | Minutes units (0–59) |
48 | 1 | Hours units (0–23) |
64 | 0 | Sync word, fixed bit pattern 0011 1111 1111 1101 |
||||
| 01 | 2 | 17 | 2 | 33 | 2 | 49 | 2 | 65 | 0 | |||||||||
| 02 | 4 | 18 | 4 | 34 | 4 | 50 | 4 | 66 | 1 | |||||||||
| 03 | 8 | 19 | 8 | 35 | 8 | 51 | 8 | 67 | 1 | |||||||||
| 04 | User bits field 1 |
20 | User bits field 3 |
36 | User bits field 5 |
52 | User bits field 7 |
68 | 1 | |||||||||
| 05 | 21 | 37 | 53 | 69 | 1 | |||||||||||||
| 06 | 22 | 38 | 54 | 70 | 1 | |||||||||||||
| 07 | 23 | 39 | 55 | 71 | 1 | |||||||||||||
| 08 | 10 | Frame number tens |
24 | 10 | Seconds tens (0–59) |
40 | 10 | Minutes tens (0–59) |
56 | 10 | Hours tens |
72 | 1 | |||||
| 09 | 20 | 25 | 20 | 41 | 20 | 57 | 20 | 73 | 1 | |||||||||
| 10 | D | Drop frame flag. | 26 | 40 | 42 | 40 | 58 | 0 | Reserved, zero | 74 | 1 | |||||||
| 11 | C | "Color frame" flag | 27 | P | Even parity bit | 43 | 1 | Binary group flag | 59 | 2 | Binary group flag | 75 | 1 | |||||
| 12 | User bits field 2 |
28 | User bits field 4 |
44 | User bits field 6 |
60 | User bits field 8 |
76 | 1 | |||||||||
| 13 | 29 | 45 | 61 | 77 | 1 | |||||||||||||
| 14 | 30 | 46 | 62 | 78 | 0 | |||||||||||||
| 15 | 31 | 47 | 63 | 79 | 1 | |||||||||||||
- Bit 10 is set to 1 if drop frame numbering is in use; frame numbers 0 and 1 are skipped during the first second of every minute, except multiples of 10 minutes. This converts 30 frame/second time code to the 29.97 frame/second NTSC standard.
- Bit 11, the color framing bit, is set to 1 if the time code is synchronized to a (color) video signal. The frame number modulo 2 (for NTSC and SECAM) or modulo 4 (for PAL) should be preserved across cuts in order to avoid phase jumps in the chrominance subcarrier.
- Bit 27, the "bi-phase mark-correction bit" is set to provide an even number of 0 bits in the whole frame, including the sync code. (As there are an even number of bits, this corresponds to the even parity rule of an even number of 1 bits.) This ensures zero net DC bias, and keeps the phase of each frame consistent so that it may be more easily read with an oscilloscope.
- Bits 43 and 59, the "binary group flag" bits, indicate the format of the user bits. 0 indicates no (or unspecified) format, while 1 indicates 4 8-bit characters. Values of 2 and 3 (i.e. bit 59 set) are reserved.
- Bit 58 is unassigned, should always be transmitted as zero, and ignored on reception.
- The sync pattern in bits 64 through 79 includes 12 consecutive 1 bits, which cannot appear anywhere else in the time code. Assuming all user bits are set to 1, the longest run of 1 bits that can appear elsewhere in the time code is 10, bits 9 to 18 inclusive.
Read more about this topic: Linear Timecode
Famous quotes containing the word data:
“This city is neither a jungle nor the moon.... In long shot: a cosmic smudge, a conglomerate of bleeding energies. Close up, it is a fairly legible printed circuit, a transistorized labyrinth of beastly tracks, a data bank for asthmatic voice-prints.”
—Susan Sontag (b. 1933)
Related Phrases
Related Words