SDDS Print Master
Guidelines
Revision 2, October 2001
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1 SDDS Print Master Format
5
Akai DD8 machines – Care and Use
14
5.1 Models
14
14
14
14
14
15
15
16
5.2 Media
5.3 At the optical camera transfer facility
5.4 Track assignment
5.5 Synchronisation at the dubbing theatre
5.6 Levels
5.7 Problems with MO drives
5.8 Drive servicing
6
SDDS - T he industry's best sounding format
17
Hear the Difference
17
17
17
17
18
19
6.2
System Basics
SDDS Products
6.4
Big Sound for the Big Screen
6.5 Further details – Why is it the best sounding system?
6.6 Testimonials
7
8
Dolby level versus operating level. Historical notes.
Subwoofers
20
21
8.1 Introduction
21
21
8.2 Setting the acoustical reference level on the dub stage.
8.3 Setting the subwoofer acoustical gain using a screen speaker as a reference.
8.4 Why we do it this way.
21
22
22
22
23
23
23
24
24
8.5 What it means.
8.6 Setting the digital screen speakers in the cinema.
8.7 Setting the digital subwoofer in the cinema.
8.8 Optical subwoofer defined.
8.9 Setting the optical subwoofer.
8.10 Subwoofer polarity.
8.11 Rule-of-thumb methods.
9
Glossary of T erms
25
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1 SDDS Print Master Format
1 SDDS Print Master Format
1.1
Media
The following ar e examples of the types of media s ui tabl e for delivering an SDDS
Printmaster. However, facilities vary from site to s ite as do cus tomer s ’ pr eferred
delivery requirements, it is therefore advis ed that you check with both the cus tomer
and the negative r ecor der site which format is required.
For negatives made in:-
Use:-
USA
DTRS Hi8
DASH
6 track magnetic f ilm
Akai DD8plus MO
DTRS Hi8
UK
Akai DD8plus MO
The r es t of Europe
DTRS Hi8 or as specified locally
1.2
T rack assignments
Audio Channel
LEFT
LEFT CENTRE
CENTRE
RIGHT CENTRE
RIGHT
SUBWOOF E R
LEFT SURROUND
RIGHT SURROUND
DASH Channel
DT RS/MO Channel
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
LEFT TOTAL (Dolby SR)
RIGHT TOTAL (Dolby SR)
11
12
N/A
N/A
OPTIONAL MATERIAL
MONO DI AL OGUE GUIDE
15
16
N/A
N/A
M&E LEFT
M&E LEFT CENTRE
M&E CENTRE
M&E RIGHT CENTRE
M&E RIGHT
M&E SUBWOOF E R
M&E LEFT SURROUND
M&E RIGHT SURROUND
17
18
19
20
21
22
23
24
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
SDDS Print Master Guidelines, Page 4 of 26
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1 SDDS Print Master Format
1.3
Synchronisation
Sampling frequency 44.1kHz. i.e. 44100 samples for every 24 frames of picture.
48kHz can be us ed, but this will be s ample-r ate-conver ted in the camer a. Make s ur e
the box is CLEARLY marked if the mas ter is at 48kHz.
T imecode 25 frames per second, referenced to 50Hz, film speed 24 fps
Or 30 frames per second, non drop fr ame, referenced to 60Hz, film speed 24fps
NOT E: For NTSC r ef er enced mixing, the mas ter tape mus t be pr e-s tr iped at
30fps/60Hz, then “pulled down” on the mixing s tage to 29.97fps NTSC s y nc wi t h
44.056kHz sampling fr equency. In this case the film speed is 23.98 fps.
Timecode mus t be r efer enced to the digital audio.
Reel 1 = 1 hour start, reel 2 = 2 hour etc.
Head pop/sync pi p should s tar t two s econds or 3 feet before the fir s t frame of
picture. e.g. for reel 1, pip at 1:00:06:00, first frame at 1:00:08:00.
1.4
Audio and levels
Operating level is –20dBfs. Wide band pink noise at the s ame RMS value as this will
produce the following S PLs in the cinema. Please note, to compar e levels of tone and
pink noise, a tr ue RMS voltmeter must be us ed. Console meter s will read differently for
tone and pink noise.
Channel
LEFT
SPL C-Weighted measurement
85
LEFT CENTRE
CENTRE
85
85
RIGHT CENTRE
RIGHT
85
85
SUBWOOF E R
LEFT SURROUND
RIGHT SURROUND
Appr ox 91 see*
82
82
*The s ubwoofer channel has 10dB of in band gain. For a full explanation of this, see
the “S ubwoofer s ” section on page 21.
T ones should be r ecor ded on all used channels at the head of each reel. 30 seconds
each of 1kHz at –20dBfs, and pink noise at the RMS level of the 1kHz tone.
Surround delay is set in the cinema pr ocessor. No delay on the mas ter .
Overlap. 2 seconds or 3 feet of audio fr om the s ubs equent reel must be r ecor ded
after the end of the r eel. This can optionally end with a tail pip.
A/D conversion. No audio pr e-emphas is .
SDDS Print Master Guidelines, Page 5 of 26
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1 SDDS Print Master Format
1.5
Media labelling
The tape or disc s houl d be labelled with:
The name of the film
The r eel number
The wor ds “SDDS master”
The language ver s ion
The date
§
§
§
§
§
The box should be labelled with the above things and als o:
The s ampling fr equency
The timecode fr ame r ate
The film speed
The tr ack assignment
Details of tones
Timecode s tar t time
Total footage
§
§
§
§
§
§
§
1.6
1.7
Checking
It is strongly recommended that all SDDS masters are played back with picture after
recording, before the optical transfer is made. A di gi tal clone could be als o made at
this time.
T est tapes
Test tapes are available fr om the S ony Cinema Pr oducts (SCP) office, details on page
Error! Bookmark not defined.. These contain 1kHz at –20dBfs plus pink noise at
the RMS value of this tone.
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2 Notes, Hints and T ips
2 Notes, Hints and Tips
2.1
Setting up the studio
The dubbing theatr e monitor ing s ys tem should be equalised to the indus tr y standard
ISO-2969 “X” curve, as used in cinemas. The method us ed to achieve this is beyond
the s cope of this text, but details can be found in the DFP-3000 Quick Start Guide,
available fr om Sony Cinema Pr oducts (SCP) office, details on page Error! Bookmark
not defined.. This is usually carried out before the pr oj ect is begun.
It is important to r ecor d the mas ter at the correct level. The audio is transferred
digitally into the camer a, with no oppor tunity for level adjustments. A r efer ence “tes t
tape” is available fr om the S CP office. Correct studio alignment can be achieved by
following thes e s teps :
Play back the 1kHz section of the S DDS test tape. This is recorded at exactly
-20dBfs.
This should r ead hous e oper ating level at the cons ole. This is usually 0VU in the
USA and 0dBu in the UK. It is also known as “Dolby Level”.
Play back the pink noise s ection of the tes t tape. Monitor each loudspeaker in
turn and s et the monitor ing levels using a S PL meter to the values shown in
section 1.4 on page 5.
§
§
§
Send 1kHz at house oper ating level to the mas ter machine. This should r ead
-20dBfs on the r ecor d machine meter s . It should als o r ead oper ating level
(unity gain) through the machine at the cons ole.
§
If no tes t tape is available:
Send 1kHz at house oper ating level to the mas ter machine, make s ur e it reads
–20dBfs at the machine meter s .
§
Check for unity gain through the machine, back at the cons ole.
Measure the output of this machine with a tr ue RMS voltmeter, and then send
pink noise at the s ame level. For 0VU operating level this is 1.23 Vrms.
Use this pink noise to s et the monitor ing levels as in section 1.4.
§
§
§
2.2
Striping and syncing
DASH and DT RS tapes should be for matted and pr e-s tr iped with timecode befor e the
session. It is imperative that the timecode and digital audio ar e locked together . The
simplest way to achieve this is to s tr ipe the tape fr om the machine’s internal
generator. The optical transfer rooms are s et up with a 25fps PAL or a 30fps B&W
NTSC video s ync. Timecode is only used for positional information. The s peed s ync
comes from the digital audio its elf, which is locked to video, and tr ans ferred digitally to
the camer a.
The r ecommended s et up for studios is to us e a mas ter video s ync, to which
everything is locked; projector, playback and mas ter machines. This will give the bes t
results. However some old pr oj ector s run from the mains only, without provision for
video s ync. In this case, timecode mus t be gener ated fr om the mains -locked pr oj ector .
This is usually OK, but it is particularly important to ens ur e the timecode to digital lock
is correct. Here we will have a s i tuati on where timecode is used for speed infor mation
SDDS Print Master Guidelines, Page 7 of 26
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2 Notes, Hints and T ips
in the dubbing theatr e and digital audio is used when the negative is made. Extra car e
must be taken.
If NT SC vi deo sync is used in the dubbing theatr e, it is very important that the
master tapes are pr e-s tr iped with 30 non-drop fr ame timecode at 60Hz. This will then
mean that the timecode tr ack, control track and A/D converter are all running at the
same s peed, second for second. 30 frames of code for 44100 samples and 24 frames
of picture. During r ecor ding of the mas ter , the machine mus t be “pulled down” using
the Fs shift function. This has the effect of locking the A/D converter with the NT S C
29.97 fps video input. This means that the machine tr ans por t, the timecode and the
A/D converter will all run slow. 29.97 fps and 44.056kHz. The pr oj ector in this case will
be r unning at 23.96 fps. Therefore 24 frames of picture will still equal 44100 samples.
NEVER stripe at 29.97 NDF. The “s econds ” of the NDF code will be of longer duration
than the “s econds ” of the contr ol track. Therefore 44100 samples of audio will not
equal 30 frames of code and 24 frames of picture.
Obviously, if a 48kHz master is required, then similar rules apply, but the r ecor ding
sampling fr equency would be 47.952kHz in this case.
2.3
Multi-format print masters
The S DDS format has been carefully designed to enable it to fit in well with other
digital audio pr int master sessions, as the monitor ing s tandar ds are compatible. The
RMS pink noise at -20dBfs specification is the s ame as DTS and S RD, however some
small differences may be found with SRD due to his tor ical RMS measurement
techniques. This is currently being addr essed by Dolby and s hor tly all formats will be
within 0.5dB. To s ave time at the s ession, the S DDS master can be taken as a par allel
feed and all masters can be r ecor ded at the s ame time. However it is very important
that the S DDS master is then played back with picture to check for errors.
2.4
Foreign language print masters
Normally the pr ocedur e is to r ecor d the mas ter along with all other formats as above,
then, if time is short, to us e the S DDS master to make the L tRt. This fold-down
process is not ideal for monitoring the mas ter , but allows the S DDS master to be
checked to s ome extent. Ideally a s epar ate playback pass should be made (clones can
be made at this time, perhaps).
SDDS Print Master Guidelines, Page 8 of 26
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2 Notes, Hints and T ips
2.5
T he importance of checking SDDS masters
Digital machines are us ually reliable in use. However they are s till prone to errors such
as:
Head errors – age or dirt
Alignment problems
Losing s ync
Slipping s ync on playback
Faulty patch leads
Tape dr op outs
§
§
§
§
§
§
§
Weird nois es from faulty converters or aliasing
It is therefore vital to listen back to all masters with picture. This will avoid cos tly
reshooting of negatives. The mas ter may not be monitor ed when it is transferred to
film as all soundtracks are s hot in one pass.
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3 DASH Machines – Care and Us e
3 DASH Machines – Care and Use
3.1
Models
There ar e five models in current use
Sony PCM3324
Sony PCM3324A
Sony PCM3324S
Sony PCM3348
Sony PCM3348HR
§
§
§
§
§
The top two machines from this list can be us ed but are not recommended. The other s
have eas y provision for Fs shift pull down and have a us eful 0.2dB per segment
calibration mode.
3.2
Head cleaning
Ensure the utmos t care when cleaning heads on these machines . Move in a s i de to
side dir ection only. Moving up and down can damage the head per manently and
replacement is extremely costly. Clean with isopropyl alcohol and an appr oved chamois
cleaning s tick.
3.3
3.4
Pre-striping
Although you can manage with advance r ecor d mode, it is far better to pr e-s tr ipe all
tapes. Format at single s peed us ing advance r ecor d with all tracks armed. SCPC does
not recommend us ing the “Pr eS tr iping” function, which formats at 4X speed.
Number of reels on a t ape
It is best to have one tape per reel, as this makes replacing r eels much easier.
However tape cos ts are high. If more than one r eel per tape is recorded, then it is
recommended that continuous timecode is recorded thr oughout the tape.
Synchronisation errors will then be minimis ed. The box must be clear ly labelled with
start and end times . There mus t be an absolute minimum of 1 minute between reels .
Five minutes is recommended.
3.5
Punch-ins
If drop-ins or punch-ins are necessary, make s ur e the cr ossfade time on the machine is
set to minimum. This is also another good r eas on for pre-formatting.
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4 DTRS Machines – Care and Us e
4 DTRS Machines – Care and Use
4.1
Models
DTRS machine ar e s emi-pr ofessional machines designed for “large” home s tudios .
They became quickly adopted as a s tandar d 8 track digital tape machine in European
dubbing s tudios . It is still often the for mat of choice for moving mater ial between
studios. There ar e two makes and s ever al models, the mos t important of which are
listed below.
Tascam DA88 – the or iginal
Sony PCM800
Tascam DA98
§
§
§
At present the S DDS masters must be in standard 16 bit format. New high bit rate
modes are now available, but the camer a s i tes only have s tandar d PCM800s and
DA88s so they can’t play back the new formats.
4.2
Levels
Note that the DA88 and PCM800 are factor y set so that +4dBu = –16dBfs. An
allowance for this has to be made if mixing with studio oper ating levels other than
0dBu (as 0dBu = –20dBfs). The machine its elf can be modified for different levels, or
console input/output trims can be us ed. If in doubt, check using the S DDS DTRS test
tape. The DA98 has software s electable levels for +4dBu = -16, -18 and – 20dBfs.
4.3
Clean air
There is a cooling fan in the DA88 and PCM800, which sucks air through the machine.
There is no filter and the only entry hole is the cassette dr awer . This means that any
dirt, cigarette s moke etc. in the air is pulled dir ectly over the heads , which is very bad
for the per for mance of the machine. It is recommended that the air around the
machines is kept as clean as possible, with no s moking in the s ame r oom. There is a
simple modification to change the dir ection of the fan and add a filter. The machine
seems to be s lightly hotter after this mod, so car eful checks must be made after war ds .
4.4
Errors
Errors can occur for a var i ety of reasons. Problems caused by dirty or worn heads can
be checked for by playing back the mas ter after recording. However, many recent
problems we have found wer e all caused by tape path misalignment. This means that
the tape will play back fine on the machine on which it was recorded, but causes errors
on other machines.
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4 DTRS Machines – Care and Us e
4.5
4.6
Compatibility
Note that there is no difference in line up pr ocedur e between the T as cam DA-88 and
the S ony PCM-800. Both machines use the s ame S ony Hi-8 transport, and both
machines are manufactur ed by T EAC.
Maintenance
Check the head hour s regularly (see below). Every 250 hours the unit should be
cleaned manually and the tape path alignment checked. This should be per for med by
an experienced engineer with the correct tools and tes t tapes. Every 1000 hours the
machine s hould be fully aligned with probable r eplacement of the pinch roller and r eel
tables and the possible r eplacement of the heads . Real world exper ience has shown
that the heads last for between 750 and 1200 hours.
4.7
Cleaning
The error rate of a known good tape s hould be checked r egular ly (see below – if the
error LED lights it’s far too late!). When the error rate begins to r is e, a cl eani ng tape
should be us ed and then the errors checked again. If there is no impr ovement, the
machine s hould be cleaned manually and r e-aligned. Note that each pass of the
cleaning tape will reduce the head life by appr oximately 5 to 10 hours. Manual cleaning
does not reduce head life, but there is a danger that the head will be damaged (tur n
anti-clockwise only) and als o the s tr ong possibility that the tape path alignment will be
altered. It is therefore always advisable to check the alignment after manual cleaning.
4.8
4.9
Head hour display
To invoke the head hour display, hold S T OP+ PL AY whilst powering on. The dis play will
say “d XXXX” where XXXX is the total head hour s
Error rate display
Hold FF+STOP+PLAY and power on. Within 2 seconds press STOP (for DA88) or PLAY
(for PCM-800). The dis play says “test”. Press REMOTE. Meters 1 and 2 now show head
errors in play mode. A “tes t” tape with a tone s hould be made when the heads are
new. The s tate of the head and alignment can then be monitor ed us ing this tape.
Newly recorded tapes should als o be checked for error rate per iodically. An “in-spec”
machine will not show anything on the meter s .
4.10 T ape gets stuck inside
If errors occur , sometimes the machine won’t eject, for “safety” reasons. To ej ect,
enter test mode as above. Instead of pressing REMOT E, press EJECT. The tape will
now ej ect. Next turn off the machine and back on to exit test mode. If the tape is
damaged, do not continue to us e the machine!
SDDS Print Master Guidelines, Page 12 of 26
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4 DTRS Machines – Care and Us e
4.11 Hints for making print masters on DT RS machines
If possible play back the mas ter in a di fferent machine to which it was recorded.
If a DA98 is available. This can be us ed in “confidence” mode. This plays back the
audio off tape whilst recording us ing r ead after write heads . Bear in mind the following
The audio output of the DA98 is delayed by 6 frames. The pr oj ector must be
advanced to compens ate for this.
§
The tr acks are ar med in pairs in this mode. Please ens ur e that no nois e, hiss
etc. is recorded on unused tr acks , especially in a 5. 1 format film. Tracks 2 and
4 LC and RC ar e s till played back in the cinema, so any noise pr es ent on them
will be r epr oduced in the cinema.
§
It is not possible to dr op-in/punch-in in this mode.
§
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5 Akai DD8 machines – Care and Us e
5 Akai DD8 machines – Care and Use
5.1
Models
There ar e two models of the DD8. Camera s i tes have the mos t recent model, which is
the DD8 plus.
5.2
Media
Masters should be s upplied on 2.6Gb MO car tr i dges , with 1 reel per side.
Note: please check with the optical transfer facility and the film distributor
before using Akai DD8 MO discs for SDDS masters. Not all optical transfer
facilities have Akai machines. It is not a s tandar d r equir ement. If you’re not sure, mix
to DT RS .
5.3
At the optical camera t r ansfer facility
The audio will be tr ans ferred digitally via AE S into the camer a. The camer a i s
synchronised to a PAL video s ync. Timecode is used for positional information, and is
synchronised with a CB electronics Bi-phase to timecode conver ter . The eas ies t and
safest method is for the camer a facility to make a “s tr ai ght across” transfer without re-
assigning tr acks , changing s ync et c. Please bear this in mind when making mas ter s .
5.4
T rack assignment
It would gr eatly help the tr ans fer facility if the s tandar d tr ack assignment is adhered
to. This can be found at section 1.2 on page 4. Tracks can be s wapped inter nally when
making clones etc. This can be s et up in two ways . Either
“routing inputs ” by pressing S YS T EM – INPUTS, or
“track mapping” by pressing S YS T EM – MORE – MORE – TRACKS. This lets
you swap r ound the output assignments of recorded tr acks .
§
§
5.5
Synchronisation at the dubbing theatre
Sampling Fr equency 44.1kHz with Film speed 24 FPS. Remember! 44100 samples for
every 24 frames of picture.
The DD8 can be s ynchr onis ed in several ways.
Video S ync ( r ecommended)
Biphase
Word s ync
§
§
§
§
Timecode only (not recommended, and will not work with NT SC pulldown)
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5 Akai DD8 machines – Care and Us e
If a PAL sync i s used, this is set up as follows
Press SYSTEM – DIGI
§
§
§
§
§
Set Sample Rate to 44.1kHz
Set Digital Sync t o PAL Video s ync
Press SYNC
Set Ext. time s our ce to 25FPS
Please note that if NTSC s y nc i s used in a “pulled down” set up, the s ampling
frequency must also be pulled down to 44.056. This is set up as follows.
Press SYSTEM - DIGI
§
§
§
§
§
Set Sample Rate to 44.056
Set Digital Sync t o NT S C 29.97
Press SYNC
Set Ext time s our ce to S MPT E 29.97 nd
Then record the mas ter in the us ual way.
5.6
Levels
Reference level = -20dBfs
It is important to s elect the correct analogue oper ating level in the DD8, as the audio
will be digitally transferred into the camer a. Therefore levels can’t be alter ed at the
optical transfer site. Use the following table as a gui de.
Studio Operating Level Set Akai ref to
T one at
+4dBu
0dBu
+2dBu
-4dBu
Gives
-20dBfs
-20dBfs
-20dBfs
-20dBfs
+4dBu or 0VU
0dBu or –4VU
+2dBu or –2VU
-4dBu or –8VU
-20
-16
-18
-12
To change the s etting on the DD8, perform the following.
Press SYSTEM – MORE – LEVELS
The level can now be changed
Press EXIT.
§
§
§
The new setting mus t be s aved, either in the pr oj ect or as a defaul t in the Flas h ROM
(recommended).
Please r emember that it is important to listen back to the S DDS master, to check for
clicks, dropouts, bad connections etc.
5.7
Problems with MO dr ives
One fault of the Akai DD8 is the fact that it doesn’t report disk reading errors. If it fails
to r etr ieve a file, it will simply mute one tr ack for, say, half a s econd, and then carry
on as normal. Otherwise it may not play a tr ack at all. These pr oblems are caus ed by:
Fragmentation – If a r eel contains a l ot of punch-ins or has been edited a l ot,
the dr ive may have pr oblems accessing all the s mall sections.
Dirt and age – it is extremely important to s er vice the dr ives regularly (see
below).
§
§
For SDDS masters it is recommended that a newl y formatted dis c i s used, and the
amount of punch-ins/editing is kept to a mi ni mum.
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5 Akai DD8 machines – Care and Us e
5.8
Drive servicing
There ar e no official service inter vals for drives, but servicing at least once a year is
recommended. Servicing can only be per for med by a s peci alist MO dr i ve s er vicing
company.
Moreover, it is absolutely vital to have no smoking in the s ame r oom as these dr ives .
They are incr edibly susceptible to air bor ne dus t and dir t. Cigarette s moke combines
the wor s t of all environments, as it is also s ticky. If you have pr oblems with MO dr i ves
and s moking occur s in the s ame r oom, this is almost certainly the r eas on for the
problems.
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6 SDDS - The indus tr y' s best sounding for mat
6 SDDS - The industry's best
sounding format
Sony Dynamic Digital Soundâ (SDDSâ) is the motion picture
industry's most advanced digital sound format, designed exclusively
for cinema presentation. In developing SDDS, Sony applied decades
of innovative experience in professional and home audio to deliver
the highest quality sound presentation. SDDS has been engineered
to give filmmakers increased creative freedom and ultimately to preserve the integrity of the
master soundtrack. With SDDS, today’s moviegoers can now experience a film's sound
exactly as heard by the director and sound engineers on the mixing stage.
6.1
Hear the Difference
Digital sound has changed the way people see movies. The
clarity and vibrance of SDDS truly heightens the movie going
experience. While other digital formats are limited to the same
5.1 channels as home systems, SDDS provides movie
audiences with up to eight channels of crystal clear discrete
audio. The additional two channels increases sonic detail and headroom adding impact to
the presentation.
6.2
System Basics
SDDS is a sound-on-film format comprised of the SDDS soundtrack, optically printed on
both edges of 35mm film and the SDDS playback hardware – a reader and processor. As
the film is projected, the SDDS soundtrack is scanned, its data is processed, and ultimately
converted into analogue audio signals for the cinema's loudspeakers and amplifiers.
6.3
SDDS Products
Sony manufactures a range of products that fit the
exhibitor's needs. For new cinemas, there is the
DFP-D3000 system that includes analogue and control
functions and can serve as the central processor in any
cinema, also available as an analogue only processor.
For retrofit applications there is the add-on DFP D2500 that simply
adds SDDS to any existing system.
Both systems use the DFP-R3000 Reader to scan the soundtrack.
The reader mounts to the top of any 35MM projector.
6.4
Big Sound for the Big Screen
The days of narrow ‘shoe box’ small screens are over. Today,
the emphasis is on making cinema going an event. There is a
trend towards building, larger, wider screens to maximise the
experience. SDDS enables filmmakers and theatre owners to
fill big auditoriums with six or eight channels of discrete digital
sound through five screen loudspeakers, two surround
channels and a full-frequency sub-woofer channel. The glory
days of 70mm big sound have returned with SDDS. None of the latest home theatre
environments can compete.
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6 SDDS - The indus tr y' s best sounding for mat
6.5
Further details – Why is it the best sounding system?
In normal operation the S DDS playback equipment uses both sides of the film for
playback. However, if one s ide is damaged, the unit will play in “digital concealment
mode”. This uses extra back up tr acks for the los t information. There is a backup
centre and s ubwoofer . The left and r ight channels are mixed to cr eate left mix backup
and r ight mix backup. These ar e played thr ough the appr opr iate s peaker s at coded
volume levels . The effect of going into “DCM” is seamless. There is always a di gi tal
centre s o dialogue is not disturbed. The two s ides are s epar ated fr om each other by
about 17 frames.
The data r ate off film is 2.2Mbits/sec, rather than 370kbits/second.
The data compr ession is Sony’s accl ai med AT RAC, used in broadcasting and in minidisk
players. The compr ession ratio is only 5:1, rather than 10:1 or 13:1.
There is no data s har i ng between channels, all channels are full range 20kHz (even the
subwoofer ).
The tr ack is printed in the cyan layer. This is the deepes t layer and ther efor e the mos t
resistant to s cr atches . The r eader s also us e patented diffuse light, which also
counteracts scratches. In normal use, with a well printed tr ack, the S DDS track will last
as long as the pictur e.
The cinema equi pment is built to S ony’s high broadcast standards. It features 28 band
digital EQ on all channels (2 band par ametr ic on the s ubwoofer ). All I/O i s balanced.
The pictur e below shows the high resolution, small dot size of SDDS (on the left).
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6 SDDS - The indus tr y' s best sounding for mat
6.6
T estimonials
“Eight channel SDDS is awesome! It makes a huge difference on Pearl Harbor. I’ve
never heard a movi e s ound s o r eal. By all means, seek out a theatr e featur ing S DDS 8
to exper ience Pear l Harbor the way we intended it. ”
Michael Bay, Director, Pearl Harbor
“The s ens e of being totally enveloped in high-detail sound was particularly noticeable
on this (SDDS 8) soundtrack”
François Groult, chief sound mixer,
“T he Messenger: T he story of Joan of Arc”
“While the incr eas ed ‘s cr een resolution’ does indeed help with the definition of busy
scenes, five channels have as much place on quiet films such as ‘Erin Brockovich’. I
always find that just having thr ee s cr een speakers on intimate films forces me to play
too many elements in the centr e hor n; otherwise, it’s distracting to have s ounds
banging ar ound the exit signs near the left and r ight speakers. With SDDS, I can use
the left-centr e and r ight-centr e s peaker s for a natur al - feeling, narrow stereo image
throughout the whole movie, going wider as necessary for exterior scenes.”
Larry Blake, supervising sound editor & rerecording mixer,
Erin Brockovich
“Movie theatr es equipped to pr es ent films in eight full channels can build and maintain
a gr eater marketing edge over home theatr es . ”
“Listening to the thr ee-channel music became an annoying and dis tr acting
disappointment, even with a 12 foot (wide) screen. Obviously my earlier notion had
been mistaken. The S DDS eight-channel advantage will work in any theatre.”
John F Allen, Boxoffice 1997
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7 Dolby level versus operating level. Historical notes.
7 Dolby level versus operating level.
Historical notes.
The current standard for digital cinema s ound has a headr oom of 20dB above the
studio r efer ence level. This is usually 0VU in USA/France/Spain/I taly and 0dBu in the
UK. If you look closely at a VU meter, 0VU is also mar ked as 100% . It now seems
ludicrous that –20dB should be mar ked as 100% . However, when the meter was first
invented, it was decided, for safety that there would be at least 10dB of headroom
above this 0VU mark. This is because the meter integrates the level over time and
gives an average r eading. It will miss instantaneous peaks. It therefore tends to under
read, depending on program material. In the film world the flux level of magnetic f ilm
was set at 0VU=185nWb/m. This allows roughly 10dB of headroom, remembering that
maximum level on magnetic t ape is not a s tr i ctl y defined point, but that the ons et of
saturation and dis tor tion is gradual. This reference level of 0VU then translated to an
SPL of 85dBc i n the cinema. With the advent of digital recording ther e is no “ons et of
tape s atur ation grey area” so it is even more impor tant to have lots of headroom to
allow for instantaneous peaks. 20dBs was decided on, which seemed to s uit the
instantaneous peaks found in film sound tr acks .
In the UK the film metering his tor y is slightly different. Reference level practises tend
to come fr om the br oadcas t sector and the BBC in particular was a gr eat setter of
standards. Here you are to find BBC PPM meter s . Marked fr om 1 to 7, with the higher
numbers being 4dBs apart. PPM4 is usually 0dBu, PPM5, 0VU. The r efer ence level is
usually 0dBu, PPM4. The maximum (broadcast) level is then PPM6, 8 dBs above
reference level. PPMs catch all the peaks so give a tr uer picture of the level. Tape flux
levels can be s et much higher. 0dBu=200nWb/m was the s tandar d agr eed on for
magnetic f ilm. These meter s are ver y convenient for mixing engineer s – dialogue
peaks about 4 and mus ic about 5 is a s i mpl e maxim.
When Dolby began their involvement with film sound and nois e r eduction in the 1970s,
they found a di fference of 0.75dB between USA and UK. This is account ed for by the
difference between 185nWb/m and 200nWb/m. The s imple r emedy for this would have
been to change the flux level alignment of the mag machines , but in some cas es the
electrical operating level was changed ins tead, with potentially confusing r es ults .
In a US A s tudi o, operating level and “Dolby level” are always the s ame. But in
Germany still today, a s i tuati on exists where Dolby level is -4.75dB with respect to
operating level. The r eas ons for this are pur ely historical and caus e enor mous
confusion. German broadcasting tr aditionally used the DI N system where the r efer ence
level was the maximum broadcast level. This was set for +6dBu=320nWb/m on
magnetic f ilm and T ype 1 PPM meter s were us ed. To make a wor l dwi de film, the
reference tone has to be 185nWb/m, which then equals 85dBc i n the cinema. It was
decided to keep the + 6dB= 320nWb/m standard and then record tone at –4.75dB with
respect to r efer ence level, this equates to 185nWb/m. This was then called “Dolby
Level”. This all worked fine, but with the ons et of digital cinema s oundtr acks , a bi z arre
-4.75dB=-20dBfs scenario was produced and the r eas ons why are being los t. To
counteract this, Dolby is now recommending that new studios follow the “Amer ican”
system of having the s ame Dolby level and r efer ence level. This makes sense as the
DIN maximum system has now largely disappear ed in the film industry.
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8 Subwoofer s
8 Subwoofers
- taken from tech note T N99051701 “setting the s ubwoofer s ”, by Craig Connelly
8.1
I ntroduction
The topic of setting s ubwoofer levels is the s ubj ect of numerous articles and even
more numer ous opinions, but of only a s i ngl e pr opos ed s tandar d (S MPT E RP 200, and
ITU 10-11R/T emp/11-E). There ar e many reasons for this. First, the us e of the moder n
digital audio s ubwoofer is unique in comparison to the other channels and it is
recorded with a di fferent monitoring r efer ence. The pur pos e of the s ubwoofer has
changed with the evolution of cinema s ound, from compensating for the poor low
frequency response and bass power capability of older screen speakers, to adding
power to low frequency effects even in theatres having full range s cr een speakers and
capable amplifiers. Secondly, different post production facilities and even different
engineer s have followed their own alignment conventions. Finally, equipment and even
meter standards are different when comparing the US A, Europe, and els ewher e. This
wordy article is only an overview and is not meant to compr is e a s peci fi c calibration
process or set of instructions.
8.2
Setting the acoustical reference level on the dub stage.
A s i gnal , generally wide band pink noise, is sent through the dubbing cons ole to each
of the monitor ing s ys tem’s screen speakers at the electrical reference level (also
known as Dolby Level). Using a r eal time thir d octave analys er , the monitor system is
adjusted for the pr eferred acous tical response at each loudspeaker, given the
properties of the louds peaker , the r oom, the s cr een, and the “X-cur ve” of SMPTE
202M. The electr ical gain of each channel in the monitor ing s ys tem is then adjusted to
give an acoustical reference level in the r oom from each screen speaker.
8.3
Setting the subwoofer acoustical gain using a scr een speaker as a
reference.
The channel used for subwoofer or LFE (low frequency effects) in the dubbing theatr e
is then adjusted as above, except that the S PL is measured differently. To make this
adjustment properly, a mul ti - channel real time analys er must be us ed. Analyser bands
in the flat-r es pons e r egion of a s cr een speaker (generally, the centr e s peaker ) are
taken as a r efer ence. These bands will not individually measure 85dB SPL, but will be
somewhat less, depending on the bandwidth of the analys er ’s bands, typically about
70 dB SPL for a 1/3-octave analys er as required by SMPT E 202M. This flat-response
region, between the low frequency roll off caused by the louds peaker cabinet and the
high frequency roll off due to the s cr een and X-cur ve, is referred to as the in-band
(acoustical) response of the monitor speaker. The s ubwoofer electrical gain is adjusted
such that the analys er channels in its in-band r egion are 10dB greater than those in
the s cr een speaker’s in-band r egion. This is referred to as “10dB of in -band gain”
(subwoofer level relative to each screen speaker level).
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8 Subwoofer s
10dB higher SPL
40
63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
40
63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
Center channel loudspeaker response
Digital subwoofer (LFE) channel response
The meas ur ement is made acous tically, not electrically. Typically, each band of the
analyser in the pass band of the s ubwoofer will then measure about 80 dB SPL. If a
screen speaker and the L FE subwoofer loudspeaker are each measured with a wide
band SPL meter, the s ubwoofer will typically measure appr oximately 5.5 dB higher.
8.4
Why we do it this way.
The r eas on for lowering the electr ically recorded level of the s ubwoofer channel and
making it up by turning up the playback gain dates back to 70mm film. The s ubwoofer
recording level was lowered to pr event saturation of the magnetic t r ack and the
playback gain was increased to compens ate. The loss of signal to nois e per for mance
was inconspicuous because the s ubwoofer signal was sent through a l ow pass filter
and did not reproduce hiss. This level difference convention has been retained in the
digital world, where it serves to give additional effective headr oom for the playback of
low frequency sound effects through the s ubwoofer loudspeaker.
8.5
What it means.
The cons equence of having 10dB more acoustical gain in the s ubwoofer monitoring
channel is that the dubbing engineer will tend to tur n down the electrical recording
level of the s ubwoofer by about 10dB compared to what she would have done without
the incr eas ed monitor gain. However, unlike the s cr een speaker channels, the engineer
does not use a cons ol e meter to check the electr ical recording level of the s ubwoofer
(except perhaps to guar d agains t overload conditions ).
8.6
Setting the digital screen speakers in the cinema.
In the cinema, the s cr een speakers are adj us ted in the almos t same manner as they
were on the dubbing s tage. This calibration, which encompasses the cinema
processor’s main fader, equalizers, power amplifiers, crossovers, loudspeakers, screen,
and r oom response, is referred to as the B-chain alignment. Consider the digitally
driven loudspeaker alignment first, as it is the mos t important. An electrical reference
signal, generally wide band pink noise gener ated within the cinema pr ocessor at a
specific l evel , is used to align each of the s cr een speakers to give the des ir ed r es pons e
(the X-cur ve or other reference r es pons e) and acoustical reference level for each
individual speaker (again, 85 dBc, slow response, measured with a wi de- band S PL
meter). This procedure ties the cinema pr ocessor’s electrical reference to an acoustical
reference in the cinema, similar to what was done on the dubbing s tage.
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8 Subwoofer s
8.7
Setting the digital subwoofer in the cinema.
In a s i milar way as on the dubbing s tage in Step 3, the level of the digital subwoofer is
set by using a mul ti - channel real time analys er and adj us ting the electrical gain of the
monitor system to achieve 10dB of in-band acoustical gain, relative to a s cr een
speaker. The cons equence of this adjustment is that signals which were r ecor ded
appr oximately 10dB lower for the s ubwoofer will now play back in the cinema at the
same acous tical level as they did when the dubbing engineer recorded them on the
dubbing s tage, because the playback conditions have been acoustically matched
between the dubbing s tage and the cinema ( as closely as variations in rooms and
loudspeakers will allow).
8.8
Optical subwoofer defined.
The optical subwoofer has a di fferent function than the digital subwoofer . It serves to
enhance the bass response of the optical playback. It is totally artificial, synthesized in
the cinema pr ocessor by combining the L , C ( -3dB), and R signals from the decoded
optical Lt,Rt and s ending the s um through a l ow pass filter. The cut off frequency of
this filter may be 50Hz, 80Hz, 100Hz, 120Hz or some other frequency, depending on
the cinema pr ocessor and the ins taller’s judgement. A hi gh pass filter may also be
applied, if it is not already a component of the optical preamplifier, to r educe low
frequency artefacts caused by ground nois e timing (GNR) errors and s tr eaking nois e
on the pr int. The end r es ult is a s i gnal containing fr equency components which overlap
those being s ent to, though not necessarily reproduced by, the s cr een speakers. In
Hollywood, the dubbing engineer may not have listened to this signal on the dubbing
stage (in part because the DS 4 without a cat. 160 card does not create it) and s o
made no ar tis tic deci s i ons based on it. It is merely an enhancement created in the
cinema to give the effect of more bass extension in the s cr een speakers and has no
correspondence to any discrete s ignal on the dub s tage. Note that it also has a much
lower dynamic r ange than the digital subwoofer signal. The digital subwoofer signal, in
contrast, was creatively recorded on its own discrete channel (Sub or LFE) of the pr int
master and is used for specific l ow frequency sound effects.
8.9
Setting the optical subwoofer.
The optical (analogue) subwoofer is adjusted to match the optical screen speakers and
effectively extend their low frequency response, again using a mul ti - channel real time
analyser to compar e bands in the pass band of a s cr een speaker and the pass band of
the s ubwoofer , and s etting in-band acoustical levels accor di ngl y. In this case, there is
no in-band acous tical gain difference, as the s ubwoofer signal is just the low frequency
components of the s cr een speaker signals.
Same SPL
40
63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
40
63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
Center channel loudspeaker response
Analog subwoofer channel response
Full range s cr een speakers need less help fr om the s ynthes ized optical subwoofer
signal than do older speakers with poor bass extension. Experienced cinema engi neer s
may chose to r educe the nominal level of the optical subwoofer , lower the fr equency
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8 Subwoofer s
of its low pass filter, or even eliminate the s ynthes ized s ignal altogether, depending on
the capabilities of the s cr een loudspeakers and the auditor ium’s acoustical response.
8.10 Subwoofer polarity.
As a s i de note, it is often difficult to deter mine the correct polarity of the s ubwoofer ,
digital or analogue. Even if pink noise is sent to the s ubwoofer and centr e channels
simultaneously, in many cases there will be no appar ent difference in combined wide
band S PL measurement when switching s ubwoofer polarity. In the end the bes t
polarity may come down to an aesthetic j udgement on the par t of the cinema
technician, based on listening to actual films.
8.11 Rule-of-thumb methods.
Measuring the level of a s ubwoofer with a wi de-band S PL meter is of questionable
value except as a r ul e- of- thumb method to r e-check a theatr e that has already been
properly calibrated. The r eas ons for this include the fact that the meas ur ed acous tical
output of a s ubwoofer (or any loudspeaker system) depends on the bandwidth of the
signal ultimately being meas ur ed. That will be affected by the bandwidth of the input
test signal, any equalizer or low pass filter settings, the auditor ium’s response, the
loudspeaker cabinet response, and the accur acy of the C weight ing r es pons e at low
frequencies of the S PL meter used for the meas ur ement. A s ubwoofer signal with a
wider bandwidth may measure the s ame as another with a narrower bandwidth but
higher level (as indicated by analyser bands within the pass band of the s ubwoofer ),
using the s ame s peaker cabinet. Considering the DFP-D3000, the bandwidth of the
pink noise s ent to the s ubwoofer is affected by a l ow pass filter that can be adj us ted
from 80Hz to 330Hz—a di fference of three octaves or eight times in acoustical energy.
No s tandar ds exist for such wide band S PL measurements of subwoofer s .
Although the meas ur ed S PL of wide band pink noise thr ough the s ubwoofer will
change if the s ubwoofer ’s low pass filter is adjusted, this will not change the actual
playback level of the digital LFE channel from film. So long as the filter frequency is
not set too low, the s ignals recorded on the dubbing s tage will determine what is
heard in the cinema when the pr oper in-band gain difference is established
acoustically, as previously described. This is why an engineer who us es a wi de- band
SPL meter to s et the digital subwoofer level is engaging in self-deception. In general, a
low pass filter setting for the digital subwoofer (LFE) of 125 Hz, 160 Hz, or even
200 Hz should s er ve in most installations, and all settings should s ound the s ame when
playing digital multichannel material. A l ow pass filter setting of 125 Hz will give a wi de
band s ubwoofer SPL pink noise meas ur ement of appr oxi matel y 91 dBc. This rule-of-
thumb r es ult is only appr oximate and s hould not be us ed for the pr imar y alignment of
a theatr e.
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9 Glossary of Terms
9 Glossary of Terms
T erm
Also Known As
Description
Sync pi p
Head pop
1kHz tone of 1 frame
duration used for
synchronizing s ound
and pictur e
Domestic ver s i on
M&E
Original version
The or iginal language
mix
International version
Music and s ound
effects only, no
language s pecific
dialogue
Dialogue pr emix
DX premix
Only the dialogue
Left total, Right total
LtRt, SR, SVA
Matrixed “analogue”
track
Confidence pass
Overlap
Control
Pull Up
Playback check
Audio after the end of
a r eel from the s tar t
of the next reel, to
facilitate manual reel
changeovers
SPL
Sound Pr essure L evel
DB full scale
Level of acoustic
sound in the air
dBfs
Level of a di gi tal
signal, where 0dBfs is
the maximum level.
Punch-in
Drop-in
The pr ocess of editing
a r ecor di ng by
pressing the r ecor d
button whilst playing
back
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9 Glossary of Terms
WWW.SDDS.COM
® Sony & SDDS are r egis ter ed tr ademar ks of the S ony Corporation
® Dolby and S RD are tr ademar ks of Dolby Laboratories
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