AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
|
| Week 10 - 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.
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'?
_________________
It's all in the ears. - Learn the concepts not the software.
Audio Courses is a way into the music business for you
|
Mon May 10, 2004 5:33 am |
|
|
hoggs33
Joined: 09 Feb 2004
Posts: 55
Location: Nottingham, England |
|
|
|
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.
This is so that they can be used to record alternative takes or as a ‘note pad’ for ideas.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
This is due to the fact that data has to be retrieved from the disk at a faster rate than normal. The rate of data transfer is one of the limiting factors on how many tracks can be played back simultaneaously.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
They provide more flexible editing and better speed of access to any part of the material.
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.
Editing can be carried out by copying info from one machine to another.
It is easy to make a back up copy from one machine to another.
Alternate takes of say a vocal could be compared by playing them back of each machine but with the backing track only on one 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 could be ‘undone’ on a digital recorder if the result were not satisfactory. With tape, once the recording is committed there is no going back to remove it.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
Sync output ensures that new tracks that are being recorded are in time withy those already on the tape.
b) why the `sync' output is required when overdubbing.
This is because the record head and playback heads are physically separate and a delay would be heard when overdubbing if sync output is not selected.
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 answer to question 1 above – think this I sthe same question.
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?
Because there are no auxiliary sends so there are no means of sending a signal to an external reverb unit.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
See answer to question 3 – again I think this is the same question!
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
An SMPTE timecode generator. – this would superimpose frames which denotes hours, minutes and seconds onto the tape.
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
MTC is based on time measured in seconds, minutes and hours rather than synchronizing to tempo speeds which is the case with MIDI clocks and song position pointers. Using MTC is more reliable as it syncs the time code of the sequencer to the 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.
Firstly the tape would be ‘striped – this basically formats the tape with a time code that the sequencer will be able to recognise. The second step would be to actually record the music onto the tape from the midi devices.
d) What is the advantage of MMC?
It enables a hard disk recording system to be remotely controlled through a midi cable.
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 multitrack would be the master and the sequencer 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?
?
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.
Dolby B, C and S
d) Give the name of another fairly common analogue noise reduction system.
DBX
e) Where would you find the ATRAC digital noise reduction system?
Mini disc recorders.
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?
The tape must be ‘striped’ with 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?
The recording level of the timecode must not be too high – see answer to question 20. the timecode should also be passed through a regerator.
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?
No because the editing process may have affected the timecode resulting in poor syncronization.
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?
Due to the editing a completely new time code ill be required so re-striping the tape would be the best option.
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?
There is likely to be bleeding between the two tracks resulting in the timecode not being clear enough resulting in poor synchronization.
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 timecode would be on the multitrack tape therefore the sequencer would be the slave and synchronize to the multitrack which would be the master.
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
Because ADAT machines have their own internal type of timecode known as A-time.
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.
I would assume that the varispeed should be carried out before transfer of the tracks to tape as the sequencer is more than likely to syncronize to the master and would then need to follow the timing on that machine.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
Such types of noise reduction entails encoding and decoding back the recorded sound. If this is carried out on a number of different systems, the noise levels will vary with each different system.
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?
It may be difficult to match the exact timecode with the tempo of the original
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?
They vocals could be put into a sampler or audio editor and time stretched to fir the tempo of the new track with then being sped up or slowed down.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
Again I would time stretch the vocals so that the pitch was not affected.
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?
The instrumental tracks should be laid down onto a multitrack recorder. The track could then be saved into a midi sequencer and attribute the MIDI tempo to the track.
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 will rewind also to the point where the video is stopped ready to play back in sync.
17. What is the frame rate of NTSC?
60 times per second
18. What is the frame rate of PAL (and SECAM)?
50 times per second
19. What is 'drop frame timecode'?
This is in connection with colour video being introduced into broadcast. When this started to happen it was necessary to make colour compatible with black and white receivers and to design colour receivers or TV’s to be able to receive black and white programming as ell. In order to accommodate the extra info needed for colour, the black and white’s 30 frame per second frame rate was slowed to 29.97 frames per second for colour. The small difference between real time and the time registered on the video can be problematic. Over a period of 1 hour (SMPTE) the video will be 3.6 second or 108 extra frames longer in relation to the real time or wall clock. To overcome this discrepancy drop frame timecode is used. In Drop frame every frame :00 &:01 are dropped for each minute change (60 x 2 = 120) except for minutes with 0’s (00:, 10:, 20:, 30:, 40:, & 50:,) (6 x 2 = 12, 120 – 12 = 108).
Haven’t really got a clue what that all means!!!!!
In simple terms the timecode skips over certain frame numbers. The frames themselves are not dropped, just the number
20. Comment on the requirements for recording timecode onto analog tape
Care must be taken over the recording levels. Timecode is a pulse waveform with sharp square edges. Analogue recording rounds off these edges to an extent, simply because it is not possible to record high frequency components of the signal at the same level as low and mid frequencies. To get around this timecode is always recorded at a fairly low level – around -7VU. This is much lower than an audio signal would be recorded, which would typically peak at around +6 VU.
21. Comment on the problems that occur when using timecode on analog tape
22. Why must timecode be regenerated when it is copied?
If timecode is just copied, the edges are rounded which would affect the performance of the timecode as it is normally recorded as a pulse waveform with sharp square edges. To copy timecode, it therefore has to be passed through the timecode generator which would be set to ‘jam sync’ The generator will lock onto the incoming code and generate fresh code with the same values at the same rate hence regenerating it.
23. What is an 'offset'?
This is a useful synchronizer function. It is when the timecode addresses on two machines are purposely set not to match, but to be at a fixed interval, or offset, in relation to each other. An example of this in use would be in replacing the second chorus of a song for some reason that didn’t sound as good as the first. The first chorus could be copied to another machine and the the two machines syncronized with an offset such that the first chorus would be dropped in exactly where the second had been. |
|
Sat May 15, 2004 4:45 pm |
|
|
|
|
griff505
Joined: 23 Feb 2004
Posts: 68
Location: Bristol |
|
|
|
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.
This allows multiple takes of the track to be recorded and stored. The takes can all be listened to, and the best take or the best parts of various takes, chosen and edited down to the one track that will be used.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
Playing back audio faster than the normal speed means that the digital audio needs to be streamed from the hard disk at a faster rate. This will reduce that amount of tracks that can be simultaneously played back. On the other hand slowing down the playback reduces the load on the hard disk as there is less demanding on the system to buffer digital audio data to the DAC.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
- Hard disk recording systems allow non-destructive editing. There are unlimited undo’s. With tape when something is edited it is much harder for the process to be undone.
- Hard disk recording systems have much easier and more complex editing tools, including the scope for the use of software plug-ins.
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.
- Two modular digital multitrack recorders, synced, allow one cassette to be used for backing tracks and maybe several cassettes for overdubs, compiling the best overdubs later onto one cassette for mixdown.
- Two modular digital multitrack recorders provide a method of making back ups of tapes.
- Two modular digital multitrack allow for more complex editing to be performed by flying tracks back and forth between machines.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
- A digital hard disk recorder allows punch-ins to be set more accurately by viewing the existing wave form - it is possible to punch in a single snare or one word of a vocal if need be.
- In a hard disk recorder the recording process is non-destructive, alternate takes can be recorded without the risk of losing a good take.
6. With reference to an analogue multi-track recorder briefly explain
a) the term ‘sync’ output - Sync output refers to the signal that comes from the record head of the multitrack tape machine - it uses the record head as a temporary sync head to allow monitoring of the recorded audio tracks
b) Why the `sync' output is required when overdubbing - Sync output is required when overdubbing because the play heads are physically located away from the record heads - if the performer was listening to the audio from the play heads their overdub would be out of sync when played back from the play heads.
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?
Yes, most machines allow ‘virtual tracks’ which allow a number of takes to be made on one track – for example on track 4 8 takes of the main vocal could be recorded, these could then be listened to and the best take selected, or the best parts of the 8 takes selected and edited down to one track.
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?
Because there are no auxiliary sends to send a signal to an external reverb processor, unless it is added to the entire mix!! Internal reverb allows each track to have reverb added only where necessary.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
- Non-destructive editing
- Easier editing
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
A tape sync machine.
b) Why is it preferable to use MTC rather than MIDI clocks and Song Position Pointers when synchronising a sequencer to a tape recorder?
(MTC = MIDI version of SMPTE) MTC is much more functional than MIDI Clock with SPP.
- When the master is fast-forwarded or re-wound the slave will immediately lock on to the direct reference point.
- If used with MMC the sequencer will chase the recorder during forward wind and rewind and then lock on to the reference point accurately when play is pressed.
- MTC runs at a higher beat resolution than MIDI clock.
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 tape must be ‘striped’ - a data track laid over the entire length of the song which can be read by a separate machine or by the sequencer itself.
- The sequenced music can be recorded to the tape as individual tracks or as a mix through the desk.
d) What is the advantage of MMC?
MIDI Machine Control when used with MIDI Time Code will allow full synchronisation functionality to a high resolution. The MMC sends messages regarding transport controls - PLAY, STOP, FORWARD, REWIND, etc - which the slave responds to. MTC locks on to the exact position and stays in sync when record or play is pressed.
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 multitrack would be the master and the sequencer 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 A (incorporate an alignment signal from the encoding processor (a warbling tone) which is recorded at the start of the tape and used to calibrate the decoding process on replay).
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
Dolby SR (incorporates an alignment signal from the encoding processor (pink noise signal) which is recorded at the start of the tape and used to calibrate the decoding process on replay.
c) Name three domestic noise reduction systems invented by the Dolby Company.
Dolby B-type noise reduction - developed in 1968 to address the hiss of slow-speed consumer tape-recording formats, such as 3-3/4 inches per second open-reel, compact cassette, and, later, the stereo linear tracks on VHS video cassette tape.
Dolby C-type noise reduction - introduced to the public in 1980, Dolby C-type provides 20 dB of noise reduction above about 1,000 Hz, fully doubling the amount given by B-type. Additional features were incorporated to deal specifically with the difficulties of recording on slow-speed consumer tape formats.
Dolby S-type noise reduction was the culmination of over 20 years experience in the design of noise reduction systems and the licensing of audio cassette decks. Just as Dolby's noise reduction technology made dramatic advances in two decades, so did the capability to manufacture quality audio cassette decks. The drive mechanisms, motors, tape heads, tape formulations and electronics had all progressed significantly over that time. Dolby took the position that if S-type were to be its premiere noise reduction technology; there should be specifications on the rest of the cassette deck to ensure the overall result would be consistent with that level of performance.
d) Give the name of another fairly common analogue noise reduction system.
DBX
e) Where would you find the ATRAC digital noise reduction system?
On Minidisk recorders - an algorithm reduces the amount of audio data produced while recording without significantly reducing the audio playback quality, a kind of intelligent compression.
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?
One track must be striped with time code.
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?
Jam sync should be used - a mode of device synchronization using SMPTE time code in which a slave device can furnish its own timing during the time that a master device is temporarily unstable. Jam sync is usually an optional mode that the user can select.
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?
The existing time code can be used as long as jam syncing is used. With jam syncing used the slave device can be instructed to ignore small dropouts of time code from the master, thus ensuring smooth synchronization. To do this, it generates its own time code whenever the master's time code is missing
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?
At this point there is no more MIDI syncing that is going to take place, therefore the tape can be erased and re-striped without any fear of a loss of synchronicity.
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?
The signal from a bass guitar will often bleed onto adjacent tracks. It sound like this has happened here and thrown the MTC converter. It is sensible practise where possible to leave empty tracks around bass 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?
The sequencer is the slave synced to the time code on the tape. The multitrack tape is therefore the 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 machines have their own time code known as A-Time – usually used to sync multiple machines together however it can be used to extract MTC and MMC information.
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.
The varispeed should take place after the other tracks have been transferred to tape. The variation in tape speed will result in the tracks on the tape having their pitch changed, therefore if other tracks were added after the tape speed change they would be out of tune with the existing tracks. Also the change in tape speed will affect the timecode pitch which may no longer sync with the slave devices.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
To carry out the process of noise reduction Dolby and dbx systems use a process of "compansion" (compression/expansion) which can cause the noise level in a recording to vary.
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 tempo of a sequencer may not match the original (which may have been recorded without a click track) exactly, also the original may have subtle changes in tempo throughout the song which may be difficult to recreate.
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 time stretched to fit the new arrangement.
- The vocals could be cut up into phrases and fitted in to match the new arrangement.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
Time-stretch the vocals to fit in with the new tempo.
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?
Some form of DAW – whether it is computer based or dedicated hardware – which allows MIDI and audio sequencing to take place, should be used. Each track should be recorded into the DAW and synchronised with the new MIDI tracks.
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 will also find the same time position on the video recorder, but it will only attempt to do this once play is pressed again on the video machine. When the video is rewinding the tape isn’t reading the time code audio track and the synchronization signal isn’t sent to the slave. When play is pressed the multitrack will rewind as fast as it can until it catches up with the master and then goes to play mode and compare it’s time code to the time code of the master.
17. What is the frame rate of NTSC?
NTSC video uses a frame rate of 30 (actually 29.97) fps which is identical to NTSC video material.
18. What is the frame rate of PAL (and SECAM)?
PAL/SECAM video uses a frame rate of 25 fps (frames per second). Source video material will be at this frame rate.
19. What is 'drop frame timecode'?
A type of SMPTE timecode designed to match clock time exactly. Two frames of code are dropped every minute on the minute except the tenth minute, to correct for the fact that colour frames occur at a rate of 29.97 fps, rather than an exact 30 fps. Drop-frame timecode is recorded with semicolons between the digits; for example, 1;00;10;02.
20. Comment on the requirements for recording timecode onto analog tape
There must be a spare track - with around 20 seconds before any other track comes in - on the tape available to receive the timecode.
21. Comment on the problems that occur when using timecode on analog tape
The signal is recorded at around 10dB below reference level, and crosstalk between tracks or cables is often a problem due to the very audible mid-frequency nature of timecode. Normally separate heads are used to record timecode to avoid crosstalk
22. Why must timecode be regenerated when it is copied?
When timecode is copied by one or more generations moderate to severe waveform distortion can occur. Therefore jam sync is used to read the degraded time code information from a recorded time code track and regenerate it into fresh code that6 can be recorded onto a new track or sent to a new media form.
23. What is an 'offset'?
Audio latency can be calculated by a DAW and a MIDI timecode offset can be worked out to ensure that processed audio always remains aligned to the MIDI tracks. |
|
Sun May 16, 2004 2:09 am |
|
|
iNSTiNCT2765
Joined: 05 Nov 2003
Posts: 60
Location: Denmark |
|
|
|
Week 10 - Synchronization
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.
This is done because you can then record more takes of the same instrument. And since they are all in sync, it is easy to switch between them and choose the one you want to use. The tracks that are stored in the hard disk as takes are called virtual tracks or v-tracks.
2. Explain why some multitrack hard disk recording systems can play back much slower than normal speed, but only a little faster.
This has to do with the speed of reading the data. It is easy to slow down the rate of data transfer from the hard disk resulting in a slower speed but if you increase the speed of transfer so the hard disk recording system plays faster, it will limit the number of tracks that can be played simultaneously.
3. State TWO major advantages of hard disk recording systems over digital tape recorders.
Since hard disk recording is non-linear as opposed to digital tape recording, it is much faster to access any part of the song simply just by pointing and clicking. And hard disk recording is also visual so it is also easier and more flexible in terms of performing editing tasks.
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 machines means that tapes can be copied for backup reasons etc.
Tapes can be edited by copying them from one machine to another using an offset.
You can have alternative vocals, backup vocals and instruments on separate tapes.
5. Explain why the punch in process on a hard disk recorder is more flexible than that on an analogue or digital tape recorder.
Taking the visual factor into account, punching in and out on a hard disk recorder has the advantage of you being able to see the exact point where you want to punch in. The process is also non-destructive giving you the security of not losing valuable audio if the punch in was not accurate. It can simply be undone and you can try again.
6. With reference to an analogue multi-track recorder briefly explain
a) the term `sync' output
The ‘sync’ output refers to the output from the recording head.
b) why is the `sync' output is required when overdubbing.
Since there is a space between the playback head and the recording head, this results in a delay between the two heads. The ‘sync’ output is used to account for this delay when overdubbing so the musician’s next performance is in sync with the rest of the multitrack tape.
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?
This is so you can record many takes of the same performance and pick the one you want to use. The number of extra takes you can store are determined by the number of v-tracks the system has.
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?
The system needs to incorporate reverb internally because there is no way to get the sound out of the system, into an external reverb unit and back into the system since there are no aux sends.
9. What are the two major advantages of hard disk recording systems over digital tape recorders?
Firstly, it is faster to locate any part of the recording on a hard disk system since it is non-linear. Secondly, the system has the visual element giving more flexible editing capabilities.
10. What piece of equipment is necessary to use a sequencer with a multitrack tape recorder?
You would need a unit to sync the sequencer to the multitrack recorder like the TS1 MIDI 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?
MTC is more accurate and follows an absolute time reference so the tape and the sequencer won’t fall out of sync. MIDI Clock messages don’t include positioning information but MTC does and this keeps the sequencer and recorder in sync at a greater resolution.
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.
First, the tape will have to be striped with time code for the full duration of the song so the sequencer and multitrack are in sync throughout the length of the song. Secondly, the sequenced material has to be recorded onto the tape individually.
d) What is the advantage of MMC?
Midi Machine Control allows you to remotely control start, stop, record, forward and backward functions.
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 multitrack is the master and the sequencer 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?
?
b) You have been given an unlabelled tape to play which starts with noise. What noise reduction system might have been used?
The Dolby system.
c) Name three domestic noise reduction systems invented by the Dolby company.
Dolby B
Dolby C
Dolby S
d) Give the name of another fairly common analogue noise reduction system.
Another NRS system is the dbx system.
e) Where would you find the ATRAC digital noise reduction system?
ATRAC or Adaptive TRansform Acoustic Coding is found on Minidiscs and the SDDS cinema surround sound format. It offers the equivalent of 52 filter bands for spectral re-analysis.
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?
The tape has to be striped with time code before it is recorded on.
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 tape needs to be first generation or the master tape to ensure that the timecode can be copied at a quality that can be read on the next tape.
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?
No it is not good practice. 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?
It wouldn’t be a problem because it is a new timecode that is being generated and not the original.
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?
The bass guitar on track 23 bleeds into track 24, which carries the timecode. This results in the timecode signal not being read properly by the sequencer resulting in the stops and loss of sync.
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 syncs to the multitrack tape recorder.
b) When working with an ADAT recorder, why wouldn’t you necessarily have to stripe the tape with timecode to synchronise a sequencer?
The ADAT recorder comes with its own sync clock independent of SMPTE.
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.
The remaining sequencer tracks should be transferred to the tape before varispeeding it or else the tracks recorded onto the tape after varispeeding won’t be in sync with the previously recorded audio.
14. Noise reduction systems such as dbx and Dolby cause the noise level in a recording to vary. Explain why this is so.
This is because these systems use an encoding and decoding procedure and the noise level will vary depending on the playback system that is used to decode the recording.
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?
You would have problems matching the tape to an exact tempo since it is likely there are slight tempo changes.
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?
I would transfer the vocals to my sequencer and cut up the vocal phrases and match them to the tempo of the remix by time stretching them.
c) Suppose you want the song to be around 15% faster in tempo. What should you do to speed up the vocals?
I would use time stretching on the vocals to make them fit the faster tempo.
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?
I would record all the instruments that are to be used into the audio/MIDI sequencer and time stretch them to match the tempo. An alternative would be to record the instruments into a sampler and stretch them in there and trigger them with MIDI.
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 will chase the video machine and sync up and play in sync when the video machine is started.
17. What is the frame rate of NTSC?
29.97 fps
18. What is the frame rate of PAL (and SECAM)?
25 fps
19. What is 'drop frame timecode'?
The 29.97 fps used by NTSC is also known as drop frame. Because it doesn’t have a whole number of frames per second, and so it doesn’t go out of sync, frame numbers 0 and 1 of the first second of every minute are not counted.
20. Comment on the requirements for recording timecode onto analogue tape
The tape should be in perfect condition and the recorder should be aligned to ensure a good timecode signal.
21. Comment on the problems that occur when using timecode on analogue tape
If the timecode isn’t recorded at a high enough level it may be a victim to cross talk and will throw the slave device out of sync. If it is recorded too high, the distortion can make the signal unrecognisable as a timecode.
22. Why must timecode be regenerated when it is copied?
Timecode needs to be regenerated due to the fact that when copying it, it can suffer quality loss and become unreadable and this can lead to sync problems.
23. What is an 'offset'?
An offset time is set at the beginning of the tape to make sure that the sequencer locks to the time code signal and is in sync with the multitrack recorder. |
|
Sun May 16, 2004 10:51 pm |
|
|
|
|
|
|
All times are GMT. The time now is Fri May 16, 2008 5:26 pm
|
|
|
|
| |
