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:
“Mental health data from the 1950’s on middle-aged women showed them to be a particularly distressed group, vulnerable to depression and feelings of uselessness. This isn’t surprising. If society tells you that your main role is to be attractive to men and you are getting crow’s feet, and to be a mother to children and yours are leaving home, no wonder you are distressed.”
—Grace Baruch (20th century)
Related Phrases
Related Words