How to digitise audio, video and film

1. Practical Session:
Digitisation Technology
Basics of Audio
Gramophone records
1/4” tape
Basics of Video
Set-up for a transfer
Special problems:
stability, colour, audio
Basic of Film
Telecine vs Datacine
Resolution, bit depth
Grading (colour
correction), workflow
4-5 September 2012 Vietnam Film Institute Workshops 1

2. Audio

Gramophone records
− Lacquer = transcription masters
− Shellac = 78s
− Vinyl = 45s, LPs

1/4” tape = 6mm tape

Many other formats, including digital: CD,
DAT, minidisc (MD), audio on videotape
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3. Grams: What the British Library Sound Archive uses
Technics turntable, made in Japan
And modified in USA by Kabusa
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4. Digitising grams (records)

Batch processing

Inspection

Cleaning

Correct playback speed

Choosing the correct needle and weight

Correct equalisation contour
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5. Batch processing

The key to efficiency

Organise item into groups of the same type
and condition

Ideally: everything controlled through the
workflow with bar codes
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6. Cleaning

Shellac: only pure de-ionized water and a
wetting agent (eg Kodak PhotoFlo)
− 1 part agent to 200 parts water

Vinyl: water and alcohol (industrial-grade
metholated spirits); mix 50-50

Can be done manually, or can buy
machines (Keith Monks, Nitty Gritty)
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7. Ultrasonic bath

This is a
standard bath,
not made
specifically for
audio work

Used for very
dirty objects,
before final
cleaning
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8. Playback Speed

Only a problem for older shellac records,
pre-1925

Speed of playback can be changed after
digitisation, so just need to 'get close'

Document what you do!

Also should check to ensure turntable is
operating at correct speed: strobe,
tachonometer (strobe built into Technics)

9. Strobe Disc
Free online
from
vinyl-
engine
4-5 September 2012 Vietnam Film Institute Workshops 9
http://www.vinylengine.com

10. Correct Needle and Weight

British Library Sound Archive uses one stylus for vinyl =
micro groove = Shure N44-7 = “0.7 mil”

Uses three sizes for shellac: 0.0028, 0.0035 and 0.0040
inches (= “4 thou” or “4 mil” or “4.0 CT”)

In metric: 1 thou = 1 mil = 25.4 micron (= μm = micro
meter) = 0.0254 mm

2.8, 3.5, 4.0 thou = 70, 90, 100μm = 0.07, 0.09, 0.1mm

The stylus will come with a recommended weight
− 1.5 to 3 grams for modern equipment
4-5 September 2012 Vietnam Film Institute Workshops 10

11. Correct Equalisation

Need a special pre-amplifier with adjustable
equalisation for recordings made before approx 1954

BUT – frequency response can be re-shaped after
digitisation if necessary
 Need RIAA
equalisation after
1954
 So –
document what
you do !
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12. Standards for Audio

Digitise at minimum of 16-bit, 44.1 kHz =
CD quality (BBC uses this)

“24-bit” at 96 kHz is IASA recommendation
− IASA TC-04 is the standard reference for
preservation-quality audio digitisation
“Guidelines on the Production and Preservation of
Digital Audio Objects” - IASA Technical Committee
Save as BWF=Broadcast Wave File= .wav + metadata
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13. Digitisation

Needs an external sound card or
equivalent – do NOT use the digitisation
built into a PC (high noise => 8 bits)

British Library recommends Rosetta from
Apogee http://www.apogeedigital.com

BBC recommends Sadie

MANY cheaper solutions possible (notes)
4-5 September 2012 Vietnam Film Institute Workshops 13

14. Audio Tape

1/4” open reel, 1950s to about 2000; 1/8”
cassette, late 1970's to now

Others: 8-track cartridge, multi-track pro

Problems: speed, track layout, tape type

More: sticky-shed, azimuth, head condition

More: Dolby noise reduction systems
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15. Open-Reel Tape Deck
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16. Speed

Cassettes usually only one speed= 1 7/8

Open reel: 15/16, 1 7/8, 3 3/4, 7 ½, 15, 30

3 ¾ and 7 ½ common for domestic use

7 ½ and 15 common for professional use

17. Track layout

Usually 2 or 4 tracks, but many
arrangements (depending upon head type,
and mono vs stereo)

Common:
− Mono 2-track
− Stereo 2-track
− Stereo 4-track

18. Two-track:
Mono and either
dual-mono or
stereo
Four track:
typical stereo
and either
stereo or dual-
mono
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Non-standard:

19. Varieties of Tape Heads
The 2 channel
heads are very
common; they can
be used for stereo
or mono.
The 4 channel can
play back most
anything.
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20. Sticky-shed

Oxide comes off the backing

Caused by absorption of moisture

Fixed by baking: 24 hrs at 45 degrees C,
with 2 to 3 hours to heat up, and 2 to 3
hours to cool down

BBC: “we don't bake” (so use tape cleaning
equipment instead)

21. Extreme Tape Shedding
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22. Azimuth

If the playback head is not at the same
angle as the record head, the high
frequencies are reduced

Solutions: 1) every tape recorder perfect;

2) adjust azimuth on playback – and listen
to high frequencies (could use meter)

Usually takes a screw driver or an Allen
key to make the adjustment

23. Heads

Worn – inspect and repair or replace

Dirty – clean after every ½ day of use !!!
− Use cotton buds and isopropyl alcohol

Magnetised – demagnetise every month

24. 4-5 September 2012 Vietnam Film Institute Workshops 24

25. Video

Much harder than audio – except for
domestic formats

Presto has online training video for 2”, 1”
and U-Matic
http://digitalpreservation.ssl.co.uk/training/2460/2542.html

Many many possible faults in playback

Use a time-base corrector, possibly a filter,
and the best colour decoder available
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26. Film

Threats: Vinegar Syndrome, shrinkage,
damage, dust

Issues: A/B rolls, splices

Wide variety of film types: reversal, B&W
vs colour, positive vs negative

Master neg, interneg, print
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27. Digitisation of Film

Telecine vs Datacine

Resolution

Bit Depth

Digital Formats

28. Telecine vs Datacine

Telecine: real-time (to videotape recorder)
− Video output (interlaced fields)
− Video resolution: SD, HD
− Video bit depth: 8 or 10 bit max
− Video aspect ratios: 12:9, 16:9

Datacine: produces a file, solves ALL the
above problems

Telecine excellent for access copies, but
poor for preservation

29. Resolution

SD 704 x 576 (480 USA)

HD 1440 x 1080 = 4x3 (1920x1080 ??)

2k 2048 x 1556 = 4x3 (almost)

4k 4096 x 3112 (maybe)
From wikipedia:
Standard Resolution Aspect R Pixels
Digital cinema 4K 4096 × 1714 2.39:1 7,020,544
Digital cinema 4K 3996 × 2160 1.85:1 8,631,360
Academy 4K 3656 × 2664 1.37:1 9,739,584
Full Aperture 4K 4096 × 3112 1.32:1 12,746,752

30. Resolution: Dutch Archive

High-level cinema (Lawrence of Arabia)
fully captured at 6000 horizontal pixels (for
a 65mm film)

Translates to 1470 for 16mm film
− Could be less for reversal stock
− And even less for 'telerecordings'
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31. Bit Depth

Dutch archive uses 10-bit log scale (which is what
most equipment produces)

Presto recommended at least 12 bits and preferably
14 bits, to capture the full range of film (number of
“stops”)

DFT scanner will capture 14 bits

Kodak: “With the advent of KODAK VISION3 Color
Negative Films, our motion picture films can capture up to
13 stops of scene content.”

For colour, it is common to ADD the number of bits in
each channel, and say “24-bit colour” – but the dynamic
range is 8 bits, NOT 24 !!!

32. Bit Depth Examples

1, 2, 4 and 8 bit illustrations:
http://en.wikipedia.org/wiki/List_of_monochrome_and_RGB_
palettes

33. 4-bit Linear vs 3-bit Log
4 bit linear = 16 steps
3 bit linear, same size steps
3 bit linear, each step twice as big
3 bit log scale, steps start small and get bigger
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34. Digital Formats for Film

DPX uncompressed, very flexible

DCI DCDM = Digital Cinema Distribution
Master: 2048x1080 (or 4096x2160) only

DCP = Digital Cinema Packaging = lossy
compressed JPEG200; (not for master)

JPEG2000 (lossless); 2:1 data reduction

Various lossy compression formats (avoid!)

And … various wrappers: MXF, AVI ...

35. Discussion

Who is doing digitisation?

What formats?

What equipment?

What results?

What problems?

36. Tea Time

Next: Digital Preservation Strategy

Format Roadmap

Digital Storage Technology

Estimating Costs

Building a Business Case

Digital Format Roadmap