AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
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| Week 10 - Synchronisation |
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1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
b) why the `sync' output is required when overdubbing.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally?
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.
d) What is the advantage of MMC?
e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave?
11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used?
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
c) Name three domestic noise reduction systems invented by the Dolby company.
d) Give the name of another fairly common analogue noise reduction system.
e) Where would you find the ATRAC digital noise reduction system?
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin?
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly?
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited? Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix?
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function?
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC convertor, the sequencer often stops or loses sync. Why?
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape?
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement?
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together?
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do?
17. What is the frame rate of NTSC?
18. What is the frame rate of PAL (and SECAM)?
19. What is 'drop frame timecode'?
20. Comment on the requirements for recording timecode onto analog tape
21. Comment on the problems that occur when using timecode on analog tape
22. Why must timecode be regenerated when it is copied?
23. What is an 'offset'?
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Mon Nov 08, 2004 7:00 am |
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aik
Joined: 03 Jun 2004
Posts: 10
Location: Glasgow |
Hi Chris
What is the difference between Question 1. and 7.???
Angelica |
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Thu Nov 11, 2004 8:43 am |
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aik
Joined: 03 Jun 2004
Posts: 10
Location: Glasgow |
Hi chris
Me again
Question 3 and 9 seem to be the same as well???
Angelica |
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Thu Nov 11, 2004 8:52 am |
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seanm
Joined: 06 Sep 2004
Posts: 20
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| week 10 task |
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hi chris please find etc.
Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.
Tracks which can be stored in sync in a hard disk recording system over and above the systems track playback limit are called virtual tracks. As many standalone hard disk recording systems have a maximum number of tracks that can be played back simultaneously “V” or virtual tracks were provided which increased the number of tracks which could be recorded and stored (alternative takes, different solos etc.) Without virtual tracks, once all eight tracks of a hard disk system limited to playing back eight tracks simultaneously, are used there is no scope for track bouncing, alternative takes etc.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
The access time and throughput of the disk in a hard disk recording system is easier to “slow” down than too speed up.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
Random access editing.
Non destructive editing
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format which records sixteen tracks on the same tape on a single machine.
Track bouncing is easier and involves no degradation of the signal as it remains in the digital domain.
Extra tapes can be employed quickly cheaply and easily with alternative takes, bounces or edits.
The Backup of whole projects onto separate tapes is quick and easy.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
With a digital or analogue tape recorder punching in is a very delicate process as mistakes cannot be rectified due to its destructive effect. With hard disk recording punching in is a non-destructive process allowing for several attempts too get it right.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
b) why the `sync' output is required when overdubbing.
Sync output refers to one of the three working modes (input output and sync) of an analogue multitrack tape recorder. The sync ouput mode enables playback and recording to take place in sync with each other. In this mode the record head doubles as a playback head.
When overdubbing tracks performers need to hear their performance in sync with the previously recorded material.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?
See previous answer
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally?
In this situation any reverb processing of signals would have to be carried out via the stereo output. If all tracks require different reverb settings all tracks will have to be processed individually. Providing reverb internally enables all tracks to be processed and played back simultaneously.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
See previous answer
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
Some digital tape machines can output MTC directly which means a sequencer can be synchronised directly requiring no additional hardware other than a midi cable.
A Smart FSK midi to tape sync unit
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
With all midi clock-based sync systems it is impossible to vary the sequencer tempo once the code has been recorded to tape. Once the sequencer has been synced up it will always play at the tempo of the code on the tape, regardless of any new changes.
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.
The first stage is to record the midi sequence in the sequencer. Once this has been done connect a midi to tape sync unit between the sequencer and the tape machine. Then playback the sequence while the time code is recorded on one track of the recorder. The tempo of the sequence determines the speed of the midi clock and hence the tempo embedded in the timecode. To play back run the recorder , playing the timecode track through the midi to tape sync unit, patching it’s midi out to the sequencers midi in, with the sequencer set to external sync mode. The two are now in sync with tape machine as the master and the sequencer the slave.
d) What is the advantage of MMC?
Midi machine control is a protocol designed to allow: midi sequencers, hard disk controllers, tape and video transports and other recording systems to be remotely controlled (from a hardware device or computer programme) via midi. MMC uses specially designed system exclusive messages throughout the midi system to devices, which can respond to MMC. MMC messages are able to communicate with individual devices within the connected “network” by assigning ID numbers to each device. This way any number of devices can be assigned to one master controlling device or programme.
e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave?
The sequencer is the master and the multitrack is the slave.
11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used?
Dolby type A, which splits the audio spectrum into four bands, compressing each (but only the quieter portions) and expanding them on playback. The amount/range of expansion is controlled by a modulated high frequency pilot tone.
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
This noise “print” is a sample of the noise on the tape utilised by Sonic Solutions “No Noise” system
c) Name three domestic noise reduction systems invented by the Dolby company.
Dolby Type A
Dolby Type B
Dolby Type S
d) Give the name of another fairly common analogue noise reduction system.
DBX Type 1
e) Where would you find the ATRAC digital noise reduction system?
ATRAC (Adaptive Transform Acoustic coding for minidisc) is an audio coding system found in Mindisc machines.
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin?
Before recording can begin the type must be “striped” with the chosen timecode.
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly?
Timecode cannot be striped onto tape without suffering moderate to sever distortion. Such distortion is exacerbated when code is copied. To overcome this a system called jam sync has been incorporated into most timecode synchronisers and midi sequencers with synchronisation capabilities. Jam sync reads the degraded time code information from a striped tape and regenerates it into fresh code that can be re-recorded onto a new track or sent to a new media form.
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited? Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix?
As an absolute timing reference this timecode is now useless.
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function?
Re-striping will simply apply a new timing reference for the whole tape. Jam sync is not required as the existing timecode can simply be erased and the new timecode recorded.
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC converter, the sequencer often stops or loses sync. Why?
This is likely to be the result of crosstalk between the tracks probably caused by recording the timecode at too high a volume. Timecode can also behave erratically if the tape does not have a dedicated synchronisation option, this allows the noise reduction of the tape machine to be switched off on the track onto which the timecode is being recorded.
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?
The sequencer synchronises (slave) to the multitrack tape (master).
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
ADAT to Midi Time Code converters do not require the tape to be striped.
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer.
Varispeeding the tape a little faster will shift the pitch (higher) of everything on tape and increase the tempo. With this in mind it would be simpler to record the rest of the sequencer tracks to tape before this is done. If the tape were speeded up first then all the midi tracks still on the sequencer would need to be repitched.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
The compansion process used by both dbx and dolby noise reduction systems involves the signal being compressed (reducing the dynamic range) before recording and expanded (increasing the dynamic range) upon playback. Because the signal was compressed prior to going to tape this minimised the tape noise as the dynamic range of the signal was compressed, it could be recorded at a higher level minimising background tape noise. Upon playback the signal is expanded downward back to its original dynamic range, a process which simultaneously downwardly expands the lower tape noise. This system does not eradicate noise but uses masking to hide it, the noise is still present and will still vary in level.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape?
The original tape would contain no timecode and slight (or excessive) shifts in tempo. This would make it difficult to synchronise the sequencer with the tape.
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement?
One solution would be to “import” the vocal into an audio/midi sequencer and edit the phrases of the vocal to fit the relatively rigid timing of the midi sequence. It might be necessary to timestretch some of the phrases.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
A 15% increase in speed will pitch up all the tracks and increase their tempo. It might be safer to first speed up the vocal on the tape and see how the voice has been affected. If this is unsatisfactory import the vocals into an audio/midi sequencer and pitch and time “squeeze” the vocal to the desired level.
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together?
Import the audio from the tape into an audio/midi sequencer and put everything together there.
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do?
The multitrack recorder will also stop and rewind to the beginning and start playing.
17. What is the frame rate of NTSC?
29.97fps (frames per second)
18. What is the frame rate of PAL (and SECAM)?
25fps (frames per second)
19. What is 'drop frame timecode'?
Drop frame timecode “drops” two frames every tenth minute. No physical frames are dropped only the timecode frame numbers.
20. Comment on the requirements for recording timecode onto analogue tape
Striping SMPTE timecode
Load the tape and rewind to start.
Connect the timecode audio output of the SMPTE device to the audio input of the highest track number. (Connect directly if possible not through the mixer)
Do not compress or alter the signal in any way.
Disable any tape noise reduction.
Select a frame rate.
Set the writing time to 00:00:00:01
Activate input monitor on the tape recorder.
Set the SMPTE device to write code.
Set the level at –7dB
Reset the SMPTE device ready to write code.
Activate record on the tape machine.
Restart time code writing and record to tape.
Label the tape box detailing: SMPTE track number, frame rate, record level, start time, duration and later the offset times for each song with tempo in bpm.
21. Comment on the problems that occur when using timecode on analogue tape
SMPTE encodes a biphase time code signal onto analogue tape in the form of a modulated square wave at a bit rate of 2400 bits/second. Recording such a signal onto analogue tape is difficult and this intrusive signal is easily corrupted by other signals.
The timecode also takes up at least one track on the tape and sometimes two when a “guard” track is left blank next to the timecode track to combat crosstalk.
Timecode cannot be striped onto tape without suffering moderate to sever distortion.
SMPTE is an audio signal and cannot be sent directly from analogue tape to a midi device, it must first be converted into a digital signal such as MTC.
22. Why must timecode be regenerated when it is copied?
Timecode cannot be striped onto tape without suffering moderate to sever distortion. Such distortion is exacerbated when code is copied. To overcome this a system called jam sync has been incorporated into most timecode synchronisers and midi sequencers with synchronisation capabilities.
23. What is an 'offset'?
An offset is used to “slip” relative times between master and slave devices. An offset is used to synchronise a slave device to a master where the master does not begin at 00:00:00:00. If for instance the relevant song starts at 00:11:24:03 it is not necessary to have over eleven minutes of blank bars in the slave sequencer, simply offset the slave by starting it at 00:11:24:03. |
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Sat Nov 13, 2004 12:51 pm |
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Rico1210
Joined: 03 Aug 2004
Posts: 39
Location: Newcastle, UK |
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Hi,
answers for Synchronisation
1. Explain why it is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously.
Having the ablilty to record and store more tracks adds flexibility to the recording and mixing process. Multiple versions of a recording can be taken and later replayed with the rest of the song to decide which version fits the best. Multitrack hard disk recording systems achieve this by using what are known as V-tracks, or 'virtual' tracks. A V-Track represents a workspace that can be used to hold recordings. This means that when recording, a system with V-tracks is not restricted to the number of tracks that can be played simultaneously but by the size of the hard disk. This enables multiple recordings to be made and copied to V-tracks which opens up the original tracks for more recordings. It also means that original recordings can be kept unchanged in case they are needed at a later point.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
Multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster because they are restricted by the speed that data can be accessed from the hard disk. It is easy for the data to be read at a slower rate than normal, but reading data faster than normal is difficult and can cause delays or audible errors during playback.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
A major advantage of hard disk recording systems over digital tape recorders is the editing process. Editing is considerably easier in a virtual environment especially using a Digital Audio Workstation, as edits can usually be undone if mistakes are made. Also, the original material can be kept. Another major advantage of hard disk recording systems over digital tape recorders is their ability to seek directly to a point in a track. The hard disk is capable of finding a particular point in a song and replaying it almost immediately, whereas a tape recorder must be rewound or fast forwarded to the desired point.
4. Describe THREE major operational advantages of having two modular digital multitrack recorders such as the ADAT or DTRS formats over a format, which records sixteen tracks on the same tape on a single machine.
Having two modular digital multitrack recorders instead of a single machine that records sixteen tracks gives the advantage of being able to record tracks or whole recordings to another tape with no loss of quality. Using more than one machine enables compilation editing by offsetting one machine against the other, then copying tracks digitally. Using two machines means that tracks can be bounced from one machine onto one track on the second machine.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
The punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder because it is non-destructive. This means that because the punch in process is in a virtual environment, the original material is not lost. This enables punch ins to be performed, checked and re-recorded easily if necessary. Using a tape based medium the original data would be overwritten during the punch in.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output.
The term sync output or sync replay is the sound replayed from the record head during overdubbing. Sync replay allows the record head to be used as a replay head for the tracks that are not currently recording. The sound quality from the record head will not always be as good as that from the replay head, but is adequate for cueing. Sometimes the sync output is provided with separate EQ to optimise the sound.
b) Why the `sync' output is required when overdubbing.
The sync output is required when overdubbing to maintain synchronisation between the tracks that are cued for the musician and the tracks being recorded. If the replay were taken from the replay head there would be a delay due to the gap between the replay head and the record head.
7. It is common for a multitrack hard disk recording system to be able to store more tracks in synchronisation than it can play simultaneously. Why is this?
See Question 1.
8. Some hard disk recording systems have mixing facilities so that several tracks can be mixed into a stereo output. If no other outputs are available why must the system incorporate reverb internally?
If a hard disk recorder had no outputs other than the main stereo output, then reverb would have to be incorporated internally in the machine because there are no outputs available to connect an external reverb unit.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
See question 3.
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
It is necessary to use a synchroniser of some kind when connecting a sequencer to a multitrack recorder to enable them to play in sync. A MIDI Tape synchroniser could be used, unless the recorder itself supports MIDI Timecode (MTC) then no extra equipment would be necessary.
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
It is preferable to use MIDI Timecode rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder because MIDI Timecode synchronises to time in hours, minutes, seconds and frames, rather than the tempo based synchronising of MIDI Clocks and Song Position Pointers.
c) If MIDI Machine Control (MMC) is not used, describe briefly the two distinct stages of operation when recording a piece of sequenced music to multitrack tape.
If MIDI Machine Control (MMC) is not used, the first stage of operation when recording a piece of sequenced music to multitrack tape would be to stripe a track of the tape with the timecode infomation. This will enable the sequencer to synchronise to the multitrack tape recorder. The second stage of operation would be to record the sequence itself to the mutlitrack tape.
d) What is the advantage of MMC?
The advantage of MIDI Machine Control (MMC) is that it enables the functions on a piece of equipment (in this case a multitrack tape recorder) to be controlled by MIDI messages. Functions such as ‘Record’, ‘Play’, ‘Stop’ and ‘Rewind’ on the tape recorder can be controlled in sync with another machine.
e) In a system using MMC, while playback or recording progresses the multitrack and sequencer will be running in sync. At this moment which is master and which is slave?
A a system using a multitrack recorder and sequencer synchronised with MMC, the multitrack recorder will be the master and the sequencer will be the slave.
11. You have been given an unlabelled tape to play which starts with a warbling tone. What noise reduction system might have been used?
The noise reduction system that will most likely have been used is Dolby A. Dolby A generates a 1kHz tone at the beginning of the tape which acts as a line-up tone.
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
If a tape starts with noise then the noise reduction system that has been used is Dolby SR (Spectral Recording). Dolby SR records a passage of Dolby Noise at the beginning of a Dolby-encoded tape to distinguish from any other line-up tones.
c) Name three domestic noise reduction systems invented by the Dolby Company.
Dolby R is a noise reduction system for consumer tape applications. Dolby C is a domestic noise reduction system sometimes incorporated into multitrack analogue recorders. The Dolby B noise reduction system is found in most cassette decks and has been around since the 1970s
d) Give the name of another fairly common analogue noise reduction system.
dbx is another common analogue noise reduction system. dbx offers two types of noise reduction, Type 1 which is used with professional equipment, and Type 2 which is used with domestic equipment.
e) Where would you find the ATRAC digital noise reduction system?
Adaptive Transform Acoustic Coding (ATRAC) is a coding system that can be found in MiniDisc recorders. It is used to split the incoming signal into three bands (below 5.5kHz, 5.5-11kHZ and above 11kHZ) and individually analyze the frequency content and level of each. ATRAC can also be found in Sony Dynamic Digital Sound (SDDS), where it is used to encode the audio data to make a substantial saving in bit rate.
12. When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used, what procedure must be carried out before any recording can begin?
When recording onto analogue or digital multitrack tape, in a situation where synchronisation is going to be used one tape track must be striped with timecode before any recording can begin. Usually this will be the outside track, which is the track with the highest number ie track 24 on a 24-track recorder.
b) Your studio manager has given you a multitrack tape containing music and timecode to copy. What must you do to ensure that the timecode is copied correctly?
The jam-sync function should be used to ensure that the timecode is copied correctly. After two or more copies the timecode on the tape will become degraded and unuseable. Jam sync synchronises the devices using SMPTE time code and instructs the slave device to ignore any errors in the timecode being copied, thus creating a smooth synchronisation.
c) A multitrack tape of a band with no sequenced instruments was striped with timecode at the start of the session and has subsequently been edited? Would it be good practice to use the existing timecode as a synchronisation reference for the console automation system during the mix?
It would not be good practice to rely on the timecode of a tape that has been edited, as the tape has probably been spliced. The tape should be re-striped with new timecode.
d) Referring to c) above, why would it not be a problem to re-stripe the tape with timecode and erase the original timecode, even if the generator does not have a jam sync function?
As there are no sequenced instruments the tape can be re-striped with timecode without causing any synchronisation problems because the tape contains the full version of the song.
e) You have striped timecode on track 24 of an analogue tape and recorded a bass guitar on track 23. When you try and synchronise a MIDI sequencer using a cheap timecode to MTC convertor, the sequencer often stops or loses sync. Why?
The sequencer often stops or loses sync because there may be cross talk from the bass guitar track onto the timecode track. Bass tracks can often bleed onto adjacent tracks.
13. When working with MIDI and multitrack tape, does the multitrack recorder synchronise to the sequencer or does the sequencer synchronise to the multitrack tape?
When working with MIDI and multitrack tape, the sequencer would synchronise to the multitrack tape.
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
ADAT recorders support MIDI Timecode(MTC). A MIDI sequencer could be connected to the MIDI out socket of an ADAT recorder, which can be set to transmit MIDI Timecode. This means a track does not have to be sacrificed for the timecode.
c) Imagine that several tracks of a MIDI sequence have been transferred to multitrack tape. The producer decides that he wants to varispeed the tape a little faster. Should this be done before or after the remaining sequencer tracks have been transferred to tape? Explain your answer.
All sequencer tracks must be transferred to tape before any varispeeding of the tape is done. If the tape was to be speeded up before some of the sequencer tracks where transferred to tape, the tracks that are already on the tape will be out of sync with the remaining sequencer tracks in terms of pitch.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary because they use a companding(compression/expansion) noise reduction system developed by Ray Dolby. The Signal-to-noise ratio improvement is accomplished by processing a signal before recording and reverse-processing the signal upon playback.
15. You have been asked to remix a song (in the sense of creating a completely new version) originally made on multitrack tape in the early 1970s.
a) What would be the main problem in synchronising a sequencer to the original tape?
Problems may be encountered when synchronising the tempo of the original tape to the sequencer. The original recording may contain tempo changes throughout.
b) If you decided only to use the vocal track from the original recording, how would you make the lines fit in time with your new MIDI sequencer arrangement?
The vocals could be made to fit in time with a MIDI sequencer by increasing their pitch, or by time stretching.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
If the song is to be around 15% faster in tempo, then the vocals would need to be time-stretched to fit in with the track.
d) The record company decides that it wants to keep a lot of the original instrumentation, but also likes your strict tempo MIDI sequence. What type of equipment should you use to put everything together?
A sampler could be used to sample the original instrumentation and then be triggered by a sequencer in time with the MIDI sequence
16. You are working with a multitrack recorder that will slave to SMPTE/EBU timecode from (for instance) a video machine, but has no other means by which it may be externally controlled. Imagine you stop the master machine, rewind the tape to the beginning and start playing. What will the multitrack do?
The multitrack recorder (slave) will rewind and play from the beginning when the play button is pressed on the video machine (master). This may cause a slight delay in sound being produced as the multitrack will have to catch up with the video machine.
17. What is the frame rate of NTSC?
The frame rate of NTSC is 29.97 frames per second (fps). This is for colour NTSC television mainly used in USA and Japan.
18. What is the frame rate of PAL (and SECAM)?
The frame rate of PAL and SECAM TV is 25 frames per second (fps). This is the European standard and is also called SMPTE/EBU.
19. What is 'drop frame timecode'?
Monochrome NTSC Television has the frame rate of 30 frames per second. When Colour NTSC television was introduced it became necessary to alter the frame rate to accommodate the colour information within the same spectrum. The frame rate was changed to 29.97 frames per second. To synchronise 30 frames per second timecode to the new rate of 29.97 it proved necessary to drop two frames every minute (except for every tenth minute) from 30 frames per second timecode in order to minimize long-term drift between the timecode and the picture.
20. Comment on the requirements for recording timecode onto analog tape.
To prevent the long-term drift between the timecode and the passage of time on the tape, timecode must be locked to the same speed reference as the tape machine. Timecode on a multitrack tape machine is usually recorded onto the outside track, which is usually track 24 on a 24-track machine. Some quarter-inch analog machines have the facility to record timecode in a track that runs through the centre of the guard band. This is called ‘centre-track timecode’.
21. Comment on the problems that occur when using timecode on analog
Long-term drift can occur between the timecode and the passage of time on the tape if the timecode is not locked to the same speed reference as the tape machine. Crosstalk between tracks can be a problem due to the audible mid-frequency nature of timecode.
22. Why must timecode be regenerated when it is copied?
When analogue tape is copied it suffers a loss of quality. Eventually the timecode would be degraded to an unreadable level, causing problems with syncronisation. This is why the timecode is regenerated when tape is copied.
23. What is an 'offset'?
An offset is when a recording is purposely placed slightly out of synchronisation. The instrument or vocal may sound better being slightly out of time with the rest of the music. |
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Sun Nov 14, 2004 2:44 pm |
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