Film processing in a digital wold, Jean Varra | Ina

#FIATIFTADubai2013 Jean Varra “film processing in a digital world

“Film processing in a digital world” Jean VARRAIna- Institut National de l’Audiovisuel. France

[email protected]



Introduction

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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.

3


Overall processing route for migration of film to digital media.

© CF9200RTI-lipsner smith

Mechanical repair

transfer to digital

telecinema SD/HD

Wet gate Colour grading

Digital restoration

scanning 2K/4K

Audio processing

Post processing

Re-splicing

Syncchecking

Editing ( news rolls)

Cleaning machine

manualCleaning

Digital media and files

Film

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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.

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

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

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

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Devices in a telecine suite

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TelecineSD/HD

Color grading system

A/V monitoring

SD/HDVideo-tape

recorder

SD/HDVideo server

Could be specific for vinegar syndrome

With or without wetgate

Digital betacamHDCAM/HDCAM SR…

May include some enhancement tools or restoration tools

Sep mag Sound Player


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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Digital cinema definitionfilm aspect ratio Horizontal Vertical 1,33:1 (academic) 2K 2048 15561,85:1 2K 2048 10802,31:1 2K 2048 8561,33:1 (academic) 4K 4096 31121,85:1 4K 4096 21602,39:1 (cinemascope) 4K 4096 1714

Pixels

17142,39:1

cinemascope

4K

2K

HDSD

4096 3112

2048 1556

1920 1080

720 576

28721,33:1 Edison

35861,66:1 Europe

39961,85:1 vista

vision


03

Criteria to choose a motion picture scanner


Important criteria to choose a motion picture scanner

criteria parametersMax 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 stabilityTests 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?

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Digital cinema definitionfilm aspect ratio Horizontal Vertical 1,33:1 (academic) 2K 2048 15561,85:1 2K 2048 10802,31:1 2K 2048 8561,33:1 (academic) 4K 4096 31121,85:1 4K 4096 21602,39:1 (cinemascope) 4K 4096 1714

Pixels

17142,39:1

cinemascope

4K

2K

HDSD

4096 3112

2048 1556

1920 1080

720 576

28721,33:1 Edison

35861,66:1 Europe

39961,85:1 vista

vision


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.

Type manufacturer

scan

resolution film format

scan speed

(images/ sec

ond) up to:

Theoritical

time to

process one

hour of film

( hours)

4K 35mm 3 8

4K 16mm 6 4

2K 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

Golden eye

Director

Scanity

Scanner comparison ( examples)

Image Systems ( ex

Digital vision)

Laser graphics

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 imagesit 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.

Diffuse illumination principles

Wet gate principles

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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

04


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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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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Typical scanning process

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Digital Archive

Scanner 2K/4K

Finishing and Post

processing unit

Hard drive server

Temporary storage and

server

Data tapeRecording

For archiving and Back up

Viewing

DPX filesDPX files

Browsing files

H264

Delivery/use formats:

HD/SD…files

16/35mm film

sound

image


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

Color grading System 2Scanner 2

Color grading system1

SAN storage server

High speed fiber network 10 GB/s

192 TB

scanner1

Digital restoration 2

Digital restoration

tool1

Sound restoration

Editing

File formats converter recording and quality

control station

ScanTemp

storageColor

grading

Digitak restoration

picture

Digitak restoration

Sound

File format conversion

file output

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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

05


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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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

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Thank you for your attention

[email protected]

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Film processing in a digital wold, Jean Varra | Ina

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