Film processing in a digital wold, Jean Varra | Ina

“Film processing in a digital world”
Jean VARRA
Ina- Institut National de l’Audiovisuel. France
jvarra@ina.fr

#FIATIFTADubai2013

Jean Varra “film processing in a digital world

Introduction

01
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• How do archive owners scan the images on film, digitize, store, and present
them for various uses: digital cinema screening, TV broadcasting, streaming
on the web… while maintaining and preserving original high quality and
viewing experience?
• For a long time, In the television world, film has been used through a telecine
transfer.
• In the digital cinema world, film scanning has been mainly used for expensive
digital restoration processes on selected films.
• Older scanners were slow and not really adapted to handle film archives and
therefore they were not considered for massive digital preservation plans.
• Today , film scanning and related processes have evolved. Faster and cheaper,
Film scanning, in a faster and faster computing and storage environment, is
more and more considered for digital preservation and makes traditional
telecine film transfer obsolete.
• The following presentation describes the technical solutions, the criteria to
choose a solution, the whole digitization chain and related activities.

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Overall processing route for migration
of film to digital media.
Mechanical repair

transfer to digital
telecinema SD/HD

Wet gate
manual
Cleaning

Film

Re
-splicing

Colour
Digital
grading restoration

Digital media
and files

Sync
Editing
checking ( news rolls)
Cleaning
machine

scanning 2K/4K

Audio
processing

Post
processing

© CF9200
RTI-lipsner
smith

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Film transfer :
telecine versus scanner

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Film transfer : telecine versus scanner
• Telecine
•A telecine turns film into digital video signals.
• It delivers pictures either in standard definition (SD) or in
High definition (HD).
• A telecine transfer is performed in real time (25 or 30
frames/s).
• Output aspect ratio is 4/3 or 16/9 whatever the original
format of film is.
• Color grading can be performed during the transfer.
• A telecine generally handles damaged films (shrinkage and
brittleness, splices…) relatively easily but wit some
“steadiness” problems
•The use of a wet gate helps to reduce the visibility of base
scratches.
•Some telecine use diffuse light systems to compensate
scratches
•Digital video signals issued from the telecine must be turned
into the expected target file format in order to be stored.

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telecine

SD

HD

definition

720*576

1920*1080

frame rate/s

25

24/25/50

aspect ratio

4/3 or 16/9

16-sept

scanning mode

interlaced

interlaced
or progressive

1,85:1 film in a 4/ 3 telecine
output
 letterbox

Academic 1,33:1 film in a 16/9
telecine output pillar box

6

Devices in a telecine suite
A/V monitoring

Telecine
SD/HD
With or
without
wetgate

SD/HD
Video-tape
recorder

Color
grading
system
Sep mag
Sound
Player

Could be
specific for
vinegar
syndrome

May include
some
enhancement
tools or
restoration
tools

Digital betacam
HDCAM/HDCAM
SR…

SD/HD
Video server

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Film transfer: telecine versus scanner
• Scanner
•A motion picture film scanner is a device used to
scan original film for storage as high-resolution
digital intermediate files.
•A scanner produces files in very high definition (2K
or 4K or more).
•The scanner scans the film frames into a File
sequence of individual frames (using high-end data
storage systems),
•The horizontal resolution is kept whatever the
original film format is.
•Vertical resolution is calculated according to the
original film aspect ratio
• Most of the scanners operate slower than in real
time ( some of them do in 2K) which can take more
time than a telecine transfer.
• Higher is the resolution to get, slower the scanning
process is.
• Color grading must be prepared and performed in
a post processing operation.
•

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4K
2872
1,33:1
Edison

2048

2K

1920
720

SD

3586
1,66:1
Europe

4096
3996
1,85:1
vista
vision

1556

3112

1714
2,39:1
cinemasco
pe

1080

576

HD

Digital cinema
film aspect ratio
1,33:1 (academic)
1,85:1
2,31:1
1,33:1 (academic)
1,85:1
2,39:1 (cinemascope)

definition
2K
2K
2K
4K
4K
4K

Pixels
Horizontal Vertical
2048
1556
2048
1080
2048
856
4096
3112
4096
2160
4096
1714

8

Criteria to choose a motion picture
scanner

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Important criteria to choose a motion
picture scanner
criteria

parameters

Max reel size

300,600m…

Accepted Film formats

16/s16/35 mm….

Resolution

2K,4K…

speed

Im/s according to expected resolution

analysis mode

CCD camera, linear scanning, surface scanning

Image signal to noise ratio

dB

Pixel size

10x10 µm,12*12µm

Quantization/ bit depth

10/12/16 bits…

Stability at splices

Either on cement or adhesive tape splices. Vertical/horizontal stability
Tests required. Amplitude of shift and or time to stabilize

Stability on grading notches

tests

Uniformity of definition and focus on warped films

Tests required

Stability over damaged perforations

Number, length..

Optical sound analysis

Ability to process and resulting quality

Availability of scratch compensation system

Type of system, wet gate or optical systems

Ergonomy

Easiness to change format/analysis system, framing, presence of PTR…

Other criteria

fast scene detection, editing lists, interconnection with post processing…

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Film quality and scanning resolution
• It is a complex issue to link analogue characteristics of a film frame
(original resolution and grain structure for example) to digital
sampling (pixels)
• The expected technical quality is determined by more parameters
than scanning resolution only. It is a balance between:
• the characteristics of the film stock itself
• ( negative , print, reversal…Resolution of a negative is generally far more
better than a release print

• the quality of the scanner:
• there are many scanners available on the market from low end to middle end
to high end ranging from 150 K€ per unit to 600 K€ per unit ,operating at
different speeds according to the expected definition/result/use.

•

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Film quality and scanning resolution
• In a usual common way, it is considered that 4 K scanning is suitable for
35mm features and 2K scanning is suitable for 16 and super16 mm.
• 4K resolution ( at least) is required to digitize a 35mm original negative
when restoration or preservation is foreseen very high processing time,
storage and costs.
• 2K resolution is likely to be good enough for making digital access
versions of 35mm films.

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Keeping original quality: How many
pixels are needed?
4096

4K
2872
1,33:1
Edison

3586
1,66:1
Europe

3112

3996
1,85:1 vista
vision
1714
2,39:1
cinemascope

2048

2K
1920
720

1556
1080

576

HD
SD

Digital cinema
film aspect ratio
1,33:1 (academic)
1,85:1
2,31:1
1,33:1 (academic)
1,85:1
2,39:1 (cinemascope)

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definition
2K
2K
2K
4K
4K
4K

Pixels
Horizontal Vertical
2048
1556
2048
1080
2048
856
4096
3112
4096
2160
4096
1714

Quality of the picture analysis system
• Most important criteria to consider are:
– Bit Depth and Light Levels : 10 12 16 bits…
– 10 bits is the minimum required when no color correction and
restoration are needed
– Higher bit depth must be preferred when some color correction
or restoration is
– higher the bit depth is, larger the file weight is..
– Pixel size of the capture sensor ( in µm)
– The signal to noise ratio of the capture system
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Storage capacity comparison
(GB/hour)
Native and compression formats

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Scanning speed
• Scanning speed is a key parameter during the digitization process if the
aim is to digitize massively the archive.
• Older scanners worked at very low speeds and were not suitable for high
volume digitization
• More recent scanners are capable of high quality scanning at speeds up to
real-time and aimed at the archive market.
• But such speeds require a powerful processing environment i.e. very fast
capturing networking and storing systems for the resulting data.
Scanner comparison ( examples)
Theoritical
time to
scan speed
scan
Type

manufacturer

process one

(images/sec hour of film

resolution

film format

ond) up to:

( hours)

Image Systems ( ex

4K

35mm

3

8

Digital vision)

4K

16mm

6

4

2K

Golden eye

16/35mm

12

2

2K

16/35mm

14

1,7

4K

16/35 mm

3

8

2K

16/35 mm

24

1

4K

16/35mm

15

1,6

Director

Laser graphics

Scanity

DFT

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Steadiness
•

Some scanners use a pin registered intermittent mechanism (moves
frame by frame) :
– Film is perfectly stable and aligned during scanning
– But they are generally slower than scanners having a continuous transport
and less tolerant to very damaged films ( shrinkage and torn perforations)

• Other scanners have a continuous transport
– They use optical methods to stabilize the image
– They produce steady results even on very damaged films

• .
• Many scanners have some difficulties to keep steadiness on physical
splices
( either glue or adhesive tapes) and image shifts more or less
vertically
and/or horizontally at splices.
• On warped films, it is important that the scanner keeps a very stable focus
• Only your own tests on a variety of your films can help you to assess
the behaviour of each type of scanner.

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Sound processing
•

Until recently ,sound processing has been considered as a separate
process.
– It is still true when processing magnetic SEPMAG

• Some scanners can now analyse optical sound at speeds different from
real time saves processing time.

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Scratches : pre- or post-scanning?
• There is a general agreement that it is better to lose/remove/fade as many
of the scratches on a film as possible at the scanning stage, rather than by
applying digital restoration software to the scanned images.
• Most of the digital restoration tools are able to remove relatively easily
random scratches but are not really efficient on vertical continuous
scratches

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Techniques to « remove » scratches
• Removing scratches at the
scanning stage may be performed
through several techniques :
– Diffuse illumination used by most
scanners will help to minimize
surface abrasions on the film base
– One technique involves capturing
and mapping an infra-red image
of the abrasions of the film and
sustract it to the imagesit only
works with color film and not on
black and white films.
– Wet-gate scanning is also possible,
but not many scanners offer this
and this technique can have an
effect on the resolution of the
image.

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Diffuse illumination
principles

Wet gate principles


Other (not less important) criteria …
• Ergonomy
– Easiness of use
– Easiness to change optics
– Smart user interface
•

fast scene change detection

•

efficient Auto focus

• Technical support
• …..

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Composition of a scanning suite

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Typical composition of a scanning
suite
• The scanner itself with options adapted to the films (sound track
player, detection of impairments, scratches reduction system, driver
computer and working interfaces….) The scanning system must
allow at least the creation of 2 types of files:
– 2K/4K high resolution files ( generally DPX) for long term
archiving and preservation of quality stored on data tapes ,LTO
for example (x2 for back up)
– A low resolution file (H264 at 1Mb/s) for browsing and viewing
stored on a hard drive server

• A temporary work space hard drive server to write and read files
• A hard drive server for viewing files
• A recording system on data tapes(LTO5/LTO6) and associated
writing software. It is important to generate a backup copy for each
data tape in order to secure date.
• Audio and video monitoring and control.
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23


Composition of a scanning suite
• ”finishing and post processing” units which can
perform:
–
–
–
–
–
–
–

Editing
Color grading
Stabilization
Noise reduction
File format conversion (DPX files to multiple formats like MPEG2, H264 AVC, DV…)
SDI/HDSDI output
Remote control for video recorders

• The finishing and post processing unit could be
used in two ways:
–

During the digitization process to remove impairments and improve quality of the picture
before storage. (film  file corrections file  storage)
– For delivery “of various use formats” (storage  file conversion delivery format)

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24


Typical scanning process
Browsing
files
H264

Hard drive server

Viewing
Delivery/use
formats:
HD/SD…files

Scanner 2K/4K
sound

DPX files

16/35mm film

Finishing
and Post
processing unit

DPX files

Digital Archive

image
Temporary
storage and
server

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25

Data tape
Recording
For archiving and
Back up


Example of scanning chain set at Ina to process Cuban
cinema news (Noticieros): preservation and restoration

Scan

Temp
storage

Color
grading

Scanner 2

Digitak
restoration
picture

Digitak
restoration
Sound

File format
conversion

Color grading
System 2

192 TB

Color grading
system1

scanner1
SAN storage
server

High speed fiber network 10 GB/s

Digital
restoration 2
Digital
restoration
tool1

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Sound
restoration

Editing

File formats
converter
recording and
quality control
station


file
output

Possible « bottlenecks » in the
workflow for a systematic massive
preservation project
•

In order to optimize the process and avoid bottlenecks , there are several
parameters to take care. Most important are
• technical parameters :
– the Scanner speed
– The temporary storage capacity simultaneous multiple
files/versions to store and handle
– The writing and play back speed (access)of data on the storage
– File format conversions and recording on data tapes
– The network bandwidth

• Working/job parameters:
– Time spent during scanning
– Time spent on color grading level of color correction to apply
– Time spent on digital restoration  level of restoration to apply (
optional)
– An optimized server administration
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File formats for film preservation

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DPX file format (.dpx)
• Digital Moving picture exchange (DPX) is a SMPTE Standard 268M-1994/2003
– DPX is a file format used to store a single frame of a motion picture or
video data stream.
– Multiple DPX files are used to store and exchange digital moving
picture sequences between a wide variety of electronic and computer
systems.
– DPX is widely used in film digital post production for digital
intermediate and storage
– Generally, uncompressed component values are stored directly as raw
data without any form of encoding very high weight of the files.
– DPX is not a container format and do no include audio tracks which
must be considered as separate files The program data is a folder
containing all the picture files and the audio files( generally Wave
files). .

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29

JPEG 2000
• JPEG 2000 or ISO/CEI 15444-1
– JPEG2000 is an Open source format based on a Wavelet compression.
– JPEG2000 is based on an Open Standard. Profiles from “lossy” to
“lossless” are available either for SD ,HD ,2K and higher…
– JPEG 2K is the recommended format for Digital Cinema ( DCI) which
currently is the only “industry standard” profile ( IMF should do that for SD
and HD)

• JPEG2000 is more and more considered as a suitable mezzanine file
format adopted by national libraries (Library of congress, Library
and archives Canada) and pushed by the majors in The US (FOX,
Warner bros for example) JPEG2000 is also more and more
considered as a compression solution for very high end and high
bit rate applications like 4K,8K…

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Other « high res » file formats
• H264 High 444
– applications range from Internet to HD. and MPEG 4 and offers several levels and profiles for
that.
– H264 High 444 is proposed to match cinema needs

• Pro RES
– is a proprietary format from Apple developed initially for use in final cut editing systems
post production.
– supports frame sizes up to 4K , SD and HD as well.
– Highest profile Pro Res 4444: perceptually lossless for high end applications. Storage and post
production exchanges.
•For mastering quality from 75Mb/s for SD to 275 Mb/s for HD and 315 Mb/s for 2K
•Containers for Apple ProRes are: quick time (.mov) or MXF

• DNX
– Proprietary format from AVIDbased on a JPEG scheme. Visually lossless quality compression
adapted to editing HD only
– Latest HD profile DNx HD444 to compete with ProRes 444 (444Mb/s)
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Storage capacity comparison
(GB/hour)
Native and compression formats

32

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Thank you
for your attention
jvarra@ina.fr

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Film processing in a digital wold, Jean Varra | Ina

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