Chapter 5 Mmr-8 System Applications; Film Post Production - Tascam MMR-8 Owner's Manual

Modular multitrack recorder

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This chapter offers more detailed information for using the MMR-8 with film and video applications.

Setup Menu parameter selections, technical background information, and block diagram connections are

also covered.

Film Post Production

A standard method of synchronizing a film transport with external audio devices (like the MMR-8) is to

use the pulse-interlock signal, or as it is more commonly known today--the biphase control signal, as a

method of generating time code from the film's movement to drive the various audio devices.

The biphase control signal consists of two 5 volt or 12-volt pulses (called phase A and phase B) that are

generated from the sprocket drive motor on the film transport. The phase relationship between the two

pulses indicates the transport direction (when phase A leads phase B by 90 the film is moving forward),

while the pulse frequency indicates the relative film speed (the nominal pulse rate indicates play speed,

with higher rates indicating wind speed and slower rates indicating crawl speed).

It is only through knowing exactly how many pulses are generated per frame, and then keeping track of

the total number of pulses that have been received (while subtracting pulses for when the film is moving

in reverse), that the MMR-8 can constantly translate the biphase signal into the correct feet & frames or

SMPTE/EBU time code numbers for the film frames. Since there are several "standard" biphase pulse

rates used by the various film transport manufacturers, there is no one nominal frequency of the biphase

signal for normal film play speed (pulse frequencies of 48 Hz up to 2400 Hz are used per frame). For the

MMR-8 to interpret and lock onto a biphase signal, and to generate the correct time code numbers, it must

be given the correct Setup parameters for the type of transport that it is following (Setup Menu 301).

Table 5.1 lists the biphase pulse rates the MMR-8 can lock to and some examples of the equipment for

each rate.

Biphase

Pulse Rate

2 ppf

4 ppf

10 ppf

20 ppf

25 ppf

50 ppf

100 ppf

ppf = pulse per frame

Table 5.1 Biphase Pulse Rate Settings

MMR-8 Tascam MMR-8 Owner's Manual • Chapter 5 • MMR-8 System Applications