We can look up 001 in the table above and see that these bits encode position 1 (cycles 3-6). Let's assume you seek to a random position in the track (by picking up the needle and dropping it somewhere) and theĭo you know what position or cycle number we are at? Unfortunately, this approach has a major problem. The first 3 cycles encode position 0, the next 3 cycles encode position 1, and so on. The corresponding signal would look like this: In reality, we want to encode a lot more different positions, which means the resulting binary number will be longer, meaning we need more bits and therefore cycles per position we want to encode. Of course, that is just a toy example, but even if we only had 8 different positions, we need use 3 bits (= 3 cycles) to represent each position. Since we're working with bits, we could simply express these decimal numbers in the base-2 (binary) numeral system, like this: Position the first position is 0, the second position is 1, the third position is 2, etc. The intuitive approach is to encode positions as a sequence of ascending numbers, e.g. Or rather: How did the engineers that created the timecode format encode the positions as bits? Encoding strategies Simple Base-2 Encoding Now it's clear how the analog timecode signal can be converted to a stream of bits.īut how can these bits be interpreted as positions? This is very convenient, because that way we don't have to lose any sleep over how to detect the peaks in the left channel, we just detect if there was a positive-to-negative zero crossing in the right channel, then take the current value of the left one and check if it's a 0 or 1 by comparing it with a threshold. ![]() If we look closely, we notice that the peaks occur every time the right channel crosses zero and the signal value goes from the positive part of the signal to negative part. The right channel is just a phase-shifted version of the left one, so we only need to look at the positive peaks of the left channel. To restore the counted number, a periodical position information is required.įor Serato timecode, this information is added to the sine wave by amplitude modulation (AM) representing the position as a series of low and high amplitudes, digital bits, where 1 is a relatively high peak, and 0 is a relatively low peak. The counted number becomes void after such an event. Unfortunately this is error prone due to crackling or a skipped groove. One can imagine to count cycles of the wave from the beginning of the control track. ![]() Getting the position out of the analog signalįrom a steady sine waveform alone, it is hard to determine in which groove the needle is and at which rotation degree the platter is moving. This is why the timecode signal also contains information that can be used to detect the needle position on the record. If you just use the pitch information, it will likely be too inaccurate to make this work, and track position and sticker position drift apart (hence the name).īoth of these problems can be solved by throwing position information into the mix. This means that if you put a sticker on the vinyl record as visual aid and then scratch the record back and forth so that the sticker is in the same position it had before the scratch, the track should also be at the same position. ![]() ![]()
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