662 lines
26 KiB
Plaintext
662 lines
26 KiB
Plaintext
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An Introduction to Tape/MIDI Sync and the MQX-32
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Dave Hocker
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Copyright (c) 1988 - All Rights Reserved
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Music Quest, Inc.
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Overview
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Since the introduction of the Music Quest MQX-32 Enhanced MIDI Co-processor
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Card, we here at Music Quest have fielded a large number of questions about
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the features of the MQX-32 and the various different forms of tape/MIDI
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sync. The purpose of this paper is to discuss the most common forms of
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sync in use by computer/music/MIDI systems, with particular emphasis on
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tape sync. In doing so, we will look at how each sync method is
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implemented. Also, we will consider the relative strengths and weaknesses.
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After you complete reading this paper, you will have a basic understanding
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of these different sync methods, and you will have a good perspective on
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the sync features of the Music Quest MQX-32 PC MIDI interface. Hopefully,
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we will have answered many of your questions, while simultaneously
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providing enough information so you can ask new ones.
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Types of Sync
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We're going to discuss four different types of sync.
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MIDI sync
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FSK (Frequency Shift Keying)
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CLS (Chase Lock Sync)
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SMPTE (Society of Motion Picture and Television Engineers)
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In our discussions, we will treat MIDI sync differently than the other
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three methods, mainly because it is not a tape sync technique, per se.
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Near the end of this paper we will discuss various converters that can
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convert from one sync source to/from another.
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Some Basic Concepts
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Before getting into the details of sync methods, we need to get a few
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basics under our belt. First let's make sure we all understand the general
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reason for sync. The term sync is used to refer to various techniques that
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allow multiple, time dependent devices to work together. For MIDIists,
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this usually means that you want to sync multiple MIDI devices together or
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that you want to sync a tape recorder with one or more MIDI devices. The
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second reason is probably the most common circumstance, as it is used to
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overcome a shortage of sound generators or synthesizers. It allows you to
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create a finished performance by reusing sound generators on separate
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tracks. That is, you make several passes on the tape, recording a new
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track on each pass.
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When you are synchronizing, you always have one master and one or more
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slaves. A good analogy is a conductor and an orchestra. The conductor is
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the master sync source who keeps all of the orchestra's musicians together.
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1
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There is another sync basic that we can draw from the conductor analogy,
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One of the roles of the conductor is to set the tempo for the orchestra.
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The conductor uses his/her baton as a "clock". The faster the baton moves,
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the faster the tempo, and vice versa.
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Another concept we need to understand is the difference between sync
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methods that are "tempo relative" and ones that are "fixed time". With a
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tempo relative sync method, the rate of the sync signals is directly
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proportional to the tempo. That is, the sync signals are generated at a
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rate that is determined by the beats-per-minute tempo. As we shall see,
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MIDI sync, FSK, and CLS are tempo relative sync methods (our orchestra
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conductor is also a tempo relative sync source).
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A fixed time sync method uses signals that are not proportional to tempo.
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The sync signals are generated at a fixed rate. Of the four sync
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techniques we will discuss, SMPTE is the only one that uses fixed timing.
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When we are synchronizing a tape recorder and MIDI devices, we use one of
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the tape tracks to store the sync information. The process of "striping a
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tape" refers to the task of writing the sync information on the sync track.
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After the tape is striped, it becomes the master source of sync signals for
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the system.
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MIDI Sync
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MIDI sync is most commonly used to allow one or more "slave" MIDI devices
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to be synchronized to a "master" MIDI device. Typically, these devices are
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sequencers or devices with "sequencer like" capability (e.g. drum
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machines). MIDI sync uses a combination of MIDI messages to accomplish its
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goal.
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ĿOut In <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E> <20>
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<20> Sequencer <20> MIDI Sync -> <20> Drum <20>
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<20> <20> <20> Machine <20>
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<20> <20> <20> <20>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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The heart beat of MIDI sync is the MIDI clock message (simply known as the
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MIDI clock). The MIDI master sends MIDI clocks at a rate of 24 clocks per
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quarter note. Hence, MIDI sync is tempo relative. MIDI devices need to
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know when to play and when to stop playing. The MIDI Start, Continue, and
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Stop messages provides these signals. When a MIDI device receives a MIDI
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Start, it plays from the beginning of its current song. When it receives a
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MIDI Stop, it ceases play. When a MIDI Continue is received, the MIDI
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device plays from the current position within the current song.
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This brings us to the MIDI Song Position Pointer (SPP) and MIDI Song Select
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(SS) messages. Simply, the SS message tells the device which song to play
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from, and the SPP tells the device where to start within that song. In
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practical application, only the SPP is used. Now, if you put the SPP
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together with a MIDI Continue, you have a most useful way to synchronize
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MIDI devices. This combination of messages essentially says "Go to this
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position within the current song and begin playing". Most often this
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2
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technique is referred to as "chase sync". Later, we will see how this
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principle is applied to CLS tape sync.
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[SPP]...[Continue] [Clock]...[Clock]...[Clock]...[Clock].....
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FSK Sync
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FSK is most commonly used to synchronize a tape recorder with MIDI devices,
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such as a sequencer or drum machine. Typically, FSK uses two distinctly
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different tones to form a sync signal (e.g 1200 Hz and 2400 Hz). One tone
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is used to fill the tape, while the second is used to mark the occurrence
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of a clock signal. As the tape is read, the sync device generates a clock
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signal every time it sees the transition from fill signal to mark signal.
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Hence, the two tones form a binary tape encoding.
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FSK sync can be found on many of the MPU-type PC MIDI interfaces. Some
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stand alone sequencers and drum machines are also capable of the writing
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and reading FSK.
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One of the advantages of FSK is that it can be written at various degrees
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of clock resolution. For example, with the MPU-type FSK, you can write a
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sync track at MIDI clock resolution (24 ticks per beat) or at the same
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resolution as the MPU's internal clock (up to 192 ticks per beat).
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In practical application, FSK sync has several draw backs. Since it is a
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purely binary signal containing no position information, you always have to
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start at the beginning of the sync track. FSK sync has no counterpart to
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the MIDI Song Position Pointer. FSK by its very nature is frequency
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sensitive, and its reliability can be greatly affected by tape quality,
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tape speed, and volume level. Finally, since FSK contains no position
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information, error recovery from tape drop outs is very difficult.
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Chase Lock Sync
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Quite simply, CLS can be described as the concept of MIDI sync applied to
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tape. That means that CLS is a tempo relative sync method. Unlike FSK,
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CLS does not use tones. Instead it uses wave forms much like those used by
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computer tape drives. The sync information is written onto the tape as a
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series of bits. Included in the sync information are song position
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pointers and MIDI clocks. Thus, when the sync track is read back, it is
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possible to locate exactly where the tape is positioned (starting from any
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place on the sync track). Usually, the sync device reads the position
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information, forms it into a MIDI song position pointer message, and sends
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it to the sequencer. The sequencer responds to the SPP by "chasing" the
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current sequence to the location indicated by the SPP (hence the term Chase
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Lock Sync). After allowing some time for the sequencer to "chase", the
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sync device sends a MIDI continue which initiates sequencing.
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CLS has one major short coming, namely its clock resolution of 24 ticks per
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beat. However, this draw back is greatly over shadowed by CLS's chase
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capability. When you use CLS with the appropriate sequencer, you can play
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and record from any location on the tape. Unlike FSK, you do not have to
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start at the beginning of the tape. Another plus for CLS is its encoding
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technique which facilitates excellent recovery from tape drop outs.
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3
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In summary, CLS is a significant step forward from FSK.
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SMPTE
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Of all the three tape sync methods being discussed, SMPTE is the only one
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for which a true standard exists (of course, MIDI is also a true standard).
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It is also the only fixed time sync method. Originally, SMPTE was
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developed for motion picture and television work. However, as we shall
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see, its utility has widened its application.
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SMPTE uses electrical signals that are similar to CLS. That is, the sync
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information is written as a string of bits. However, SMPTE uses the
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concept of a "frame" instead of MIDI concepts such as song position pointer
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and MIDI clocks. A SMPTE frame is a group of bits that describe a single
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location on the tape (called the frame address). The number of bits that
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make up the frame, the rate at which the bits are written to tape, and the
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number of frames per second are dependent on the SMPTE format. In the US,
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the two 30 frame formats (30 frames per second) are used most of the time.
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These formats use a frame that is 80 bits long, written at a rate of 2400
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bits per second. Each frame address contains a complete time stamp in
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terms of hours, minutes, seconds, and frame number. Most often, you see
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this written in the form:
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HH:MM:SS:FR
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Thus 01:37:22:19 identifies the frame address as frame 19, at 1 hour, 37
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minutes, 22 seconds. (If you are completely new to this topic and you
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watch MTV, you can occasionally see videos with SMPTE consoles showing a
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rolling frame address. The Cheap Trick video "The Flame" is a good
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example).
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Overall, there are four standard SMPTE formats:
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24 frame used by motion pictures.
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25 frame used in Europe for video work because the
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television scan rate is 25 frames per second.
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30 frame non-drop format used world wide for audio sync.
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30 frame drop format used in the US for video work. US color
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television uses a scan rate 29.97 frames per
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second. The term "drop" format comes from the
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fact that this format is identical to 30 frame
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non-drop, except that selected frames are
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periodically dropped to yield an overall scan
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rate of 29.97 frames/second.
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As previously mentioned, in the US, the 30 frame formats are most
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prevalent. The 30 frame non-drop format is predominantly used for audio
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sync. The 30 frame drop format is used for video/audio sync work, such as
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scoring a video tape.
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Practically speaking, SMPTE offers more advantages than any other form a
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synchronization. This may not be immediately obvious, since we haven't
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said anything about how SMPTE can be used. However, it is clear that SMPTE
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is wave of the future.
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4
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Several aspects of SMPTE give it a distinct advantage over all of the other
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forms of tape sync. First, SMPTE is a standard that has been in use for
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some time. A tape written by a SMPTE writer can be read by any SMPTE
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reader that supports the given format. For example, if you write a tape in
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30 frame non-drop format, then any reader capable of reading 30 frame non-
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drop format can read the tape. While MIDI sync is a standard, FSK and CLS
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are not. Every manufacturer's FSK and CLS formats are proprietary
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(although Roland's FSK sync has been used by other manufacturers), and
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hence interchange of tapes is generally not practical.
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As further evidence of the value of this standard, SMPTE has been adopted
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into the world of MIDI through the MIDI Time Code extension. With out
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going into too much detail, MIDI Time Code messages allow SMPTE frame
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addresses to be sent over MIDI cables, in real time. Thus, there is
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already a tight binding between SMPTE and MIDI. We'll talk more about
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SMPTE and MIDI when we look at SMPTE to MIDI Time Code converters.
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Second, SMPTE's fixed time format gives it more flexibility than FSK or CLS
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tape sync. If you stripe a tape with FSK or CLS, and then decide you want
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a different tempo or set of tempos, you must rewrite the tape. With SMPTE
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and the appropriate sequencer, you can change tempos at any time without
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the necessity of rewriting the sync track.
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Third, like CLS tape sync, you can start reading a SMPTE track at any
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location. SMPTE's encoding scheme also greatly facilitates recovery from
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tape drop outs.
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Finally, SMPTE can be used as a trigger mechanism with power and
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simplicity. For example, using SMPTE it is easy to visualize starting a
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sequence at location 00:03:02:00 (i.e. 3 minutes, 2 seconds into the tape).
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It is just as easy to visualize that at that location on a video is a car
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crash and that you want your sequencer to fire a set of notes to a sampler
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which in turn will play the sound of the crash.
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With all of these advantages it is difficult to see any short comings with
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SMPTE. Probably the only draw back is the current shortage of SMPTE
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applications for the IBM PC world. However, with the introduction of the
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Music Quest MQX-32 PC MIDI interface and the Yamaha C-1 music computer
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(which both have SMPTE), many developers are quickly moving to fill this
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void.
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Sync Converters
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A sync converter is an external "box" that translates one form of sync into
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another. For the most part, sync converters are used to translate a tape
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sync format into some form of sync that is recognized by MIDI (either MIDI
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sync or MIDI Time Code).
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5
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FSK to MIDI Sync
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An FSK to MIDI sync converter can produce FSK tape sync from MIDI sync
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messages (the striping process). Conversely, as it reads an FSK sync
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track, it produces MIDI sync. The Yamaha YMC-10 is an example of an FSK to
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MIDI sync converter.
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ĿOut In <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E> <20>
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<20> MIDI <20> <20> FSK to MIDI Sync <20>
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<20> Device <20> <- MIDI Sync -> <20> Converter <20>
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<20> <20><<3C><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ <20>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>In Out<75><74><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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In<49> ^ <20>Out
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<20> FSK <20>
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Out<75> v <20>In
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> Tape <20>
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<20> Deck <20>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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Chase Lock Sync
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There are several Chase Lock Sync devices on the market, such as the J.L.
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Cooper PPS-1, Synhance MTS-1, and Tascam MTS-30. The Music Quest MQX-32 PC
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MIDI interface features built in CLS.
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CLS boxes perform just like FSK to MIDI sync converters. Their distinct
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advantage lies with the advantages of CLS, namely the ability to use song
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position pointer to play from any tape location.
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ĿOut In <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E> <20>
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<20> MIDI <20> <20> CLS Sync <20>
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<20> Device <20> <- MIDI Sync -> <20> Box <20>
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<20> <20><<3C><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ <20>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>In Out<75><74><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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In<49> ^ <20>Out
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<20> CLS <20>
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Out<75> v <20>In
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> Tape <20>
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<20> Deck <20>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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SMPTE to MIDI Sync
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SMPTE to MIDI sync converters provide capabilities similar to CLS sync
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converters. However, they offer distinct advantages by virtue of their use
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of SMPTE as the tape sync method.
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6
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> <20> <20> <20>
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<20> MIDI <20> <20> SMPTE to MIDI Sync<6E>
|
||
<20> Device <20> <- MIDI Sync <20> Converter <20>
|
||
<20> <20><<3C><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ <20>
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>In Out<75><74><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
|
||
In<49> ^ <20>Out
|
||
<20> SMPTE <20>
|
||
Out<75> v <20>In
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
|
||
<20> Tape <20>
|
||
<20> Deck <20>
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
|
||
|
||
|
||
Because SMPTE is a fixed time sync method, it does not require an input
|
||
signal to stripe a tape. Thus, SMPTE to MIDI sync converters do not
|
||
require MIDI sync input during the striping process.
|
||
|
||
The playback process is somewhat more complicated; however, it is
|
||
correspondingly more flexible. Most SMPTE to MIDI converters require that
|
||
you give them sort of a tempo map. There are several ways that this can be
|
||
accomplished. One way is to tell the converter what MIDI sync tempos
|
||
should be in effect at what SMPTE frame addresses. For example at frame
|
||
00:00:00:00, you might want to start with a tempo of 120 beats/minute.
|
||
Then, at frame 00:01:00:00 (one minute into the sync track), you might want
|
||
the tempo to change to 140 beats/minute.
|
||
|
||
A second way to enter a tempo map is to tell the converter box pertinent
|
||
operating parameters so that the converter can determine the appropriate
|
||
tempo. For example, you could tell the converter that you want to play
|
||
measure 1 starting at 00:00:00:00 and that you want measure 30 to finish at
|
||
00:01:00:00. Assuming 4 beats/measure, the converter would calculate that
|
||
a tempo of 120 beats/minute would be the appropriate tempo.
|
||
|
||
The necessity of entering a tempo map into an external converter box
|
||
illustrates one of the potential draw backs of such a device. If the MIDI
|
||
software you use is not capable of automatically loading the tempo map
|
||
information into the converter box or if the converter box is not capable
|
||
of being totally set up via MIDI, you may find that you have to do it
|
||
manually.
|
||
|
||
Two examples of SMPTE to MIDI converters are the Roland SBX-80 and Imagine
|
||
Computer's SMPTE City. The Music Quest MQX-32 PC MIDI interface in
|
||
combination with the appropriate software can perform the same functions as
|
||
any of these products, including the management of the tempo map.
|
||
|
||
|
||
|
||
SMPTE to MIDI Time Code
|
||
|
||
A SMPTE to MTC converter is capable of reading and writing SMPTE tape sync
|
||
and translating the frame addresses into MIDI Time Code messages. Because
|
||
MIDI Time Code is relatively new, not too many products of this nature are
|
||
available. The value of such a product is to broadcast the equivalent of
|
||
SMPTE sync over a MIDI network.
|
||
|
||
|
||
7
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
|
||
<20> <20> <20> <20>
|
||
<20> MIDI <20> <20> SMPTE to MTC <20>
|
||
<20> Device <20> <- MIDI Time Code <20> Converter <20>
|
||
<20> <20><<3C><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ <20>
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>In Out<75><74><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
|
||
In<49> ^ <20>Out
|
||
<20> SMPTE <20>
|
||
Out<75> v <20>In
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
|
||
<20> Tape <20>
|
||
<20> Deck <20>
|
||
<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
|
||
|
||
The use of MTC converters in the IBM PC world has been limited until
|
||
recently. This is mostly because widely extant MPU chip set based
|
||
interfaces do not recognize MIDI Time Code messages. As a result, most IBM
|
||
PC software developers have not been able to take advantage of SMPTE to MTC
|
||
converters. However, the Music Quest MIDI Co-processor Card and the MQX-32
|
||
Enhanced MIDI Co-processor Card are fully capable of handling MTC messages.
|
||
|
||
The J.L. Cooper PPS-1 is an example of a converter that is capable of
|
||
producing MIDI Time Code while reading SMPTE. The Music Quest MCC is
|
||
capable of receiving MTC messages from a SMPTE to MTC converter. The Music
|
||
Quest MQX-32 PC MIDI interface can produce MIDI Time Code while writing and
|
||
reading SMPTE, and it is capable of receiving MIDI Time Code from an
|
||
external MTC source (such as a PPS-1 or another MQX-32).
|
||
|
||
|
||
The Future for Tape Sync
|
||
|
||
As we have seen, tape sync has gone from the basic capability of FSK sync
|
||
to the power of CLS and SMPTE. The popularity of SMPTE is on the rise, and
|
||
it appears that over the next year it will become THE tape sync method.
|
||
The introduction of inexpensively priced SMPTE capable interfaces to the
|
||
broad based world of the IBM PC should further speed this movement. Look
|
||
for a wide variety of new SMPTE based products to be introduced into the PC
|
||
world over the next 12-18 months, as software developers rush to fill the
|
||
current void.
|
||
|
||
You can expect to see mainstream software companies such as Twelve Tone
|
||
Systems, Magnetic Music, and Voyetra introduce new or enhanced products
|
||
based on their current sequencer product line. All of these products will
|
||
exploit SMPTE to some degree. It is likely that you will see the
|
||
introduction of totally new products for use with SMPTE. A product based
|
||
on the concepts of Digidesign's Cue Sheet is almost certain to appear.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
8
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
The Music Quest MQX-32 PC MIDI Interface
|
||
|
||
The MQX-32 is the latest addition to the Music Quest PC MIDI interface
|
||
product line. As the preceding discussion has illustrated, it provides a
|
||
significant set of sync features. Furthermore, the MQX-32 is upward
|
||
compatible with the MIDI Co-processor Card, as well as interfaces based on
|
||
the Roland MPU chip set.
|
||
|
||
MQX-32 Features
|
||
|
||
The MQX-32 incorporates many new features not found in current PC
|
||
interfaces.
|
||
|
||
Two separate MIDI-out ports allowing PC software to support two separate
|
||
MIDI paths or a total of 32 MIDI channels.
|
||
|
||
Chase Lock Tape Sync. The MQX-32 can "stripe" a tape so that it can be
|
||
started from any location. When the tape is played, the MQX-32
|
||
generates a Song Position Pointer which allows a PC sequencer to "chase"
|
||
to the current tape location. Unlike ordinary FSK sync, CLS allows you
|
||
to start from any place on the tape.
|
||
|
||
SMPTE. The MQX-32 can write and read 30 frame drop and non-drop SMPTE
|
||
format. The MQX-32 is capable of generating MIDI Time Code during SMPTE
|
||
reading, so that outboard MIDI devices can respond to the MIDI Time Code
|
||
messages. SMPTE support includes a "cue point" facility which
|
||
simplifies the development of PC based SMPTE software.
|
||
|
||
MIDI Time Code support. The MQX-32 can receive MIDI Time Code messages
|
||
from MIDI-in. MIDI Time Code and SMPTE are implemented so that PC
|
||
software sees them as identical sync sources (i.e. the "cue point"
|
||
facility works with both).
|
||
|
||
Software Support
|
||
|
||
All software that runs on the current MIDI Co-processor Card will run on
|
||
the MQX-32. All existing PC sequencers that support Song Position Pointer
|
||
based MIDI sync will work with the MQX-32's Chase Lock Sync. This
|
||
includes:
|
||
|
||
Cakewalk
|
||
Forte
|
||
Sequencer Plus
|
||
|
||
The following companies have made commitments to support the MQX-32's new
|
||
features:
|
||
|
||
Twelve Tone Systems (Cakewalk)
|
||
Magnetic Music (Texture)
|
||
LTA Productions (Forte)
|
||
Imagine Group (Master Series)
|
||
Club MIDI (ProLib)
|
||
The MIDI Connection (Tape 'n' Step).
|
||
|
||
|
||
|
||
|
||
9
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Trademarks
|
||
|
||
All trademarks are the property of their respective companies.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
10
|
||
|
||
|