Coding techniques for Coding techniques for digital cinemadigital cinema

Andreja SamAndreja SamčovićčovićUniversity of BelgradeUniversity of Belgrade

Faculty of Transport Faculty of Transport and and Traffic EngineeringTraffic Engineering

IntroductionIntroductionFilm is the best presentation format for cinema contentFilm is the best presentation format for cinema content

FFilm is already being replaced by digitally contentilm is already being replaced by digitally content

Archives worldwide Archives worldwide - - to ingest, store, manage, conserve, to ingest, store, manage, conserve, access and preserve efficiently film content in digital access and preserve efficiently film content in digital formform

EEasy and economical access to digital versionasy and economical access to digital version

Digital cinema (DC) intends to meet these requirements Digital cinema (DC) intends to meet these requirements

BBest quality and uncomplicated access to the stored est quality and uncomplicated access to the stored itemsitems

Digital Cinema InitiativesDigital Cinema Initiatives

In recent years, digital multimedia devices In recent years, digital multimedia devices become more and more popular in people’s daily become more and more popular in people’s daily life life With the development of digital technology, With the development of digital technology, digital cinema has been putting into practice digital cinema has been putting into practice Digital cinema is a new kind of application for Digital cinema is a new kind of application for super high definition videosuper high definition videoTo establish an industrial standard for digital To establish an industrial standard for digital cinema, a joint venture of 7 major Hollywood cinema, a joint venture of 7 major Hollywood studios, Digital Cinema Initiatives (DCI), founded studios, Digital Cinema Initiatives (DCI), founded in March 2002, and put forward specification in in March 2002, and put forward specification in 20052005

Digital Cinema InitiativesDigital Cinema Initiatives

The DCI (Digital Cinema Initiative) specification The DCI (Digital Cinema Initiative) specification published in 2005 has selected JPEG2000 instead of published in 2005 has selected JPEG2000 instead of H.264 as the video coding standard for digital cinema H.264 as the video coding standard for digital cinema It shows that JPEG2000 has a better performance in the It shows that JPEG2000 has a better performance in the field of super high definition video coding field of super high definition video coding Until now, only a few basic tests have been done to Until now, only a few basic tests have been done to compare between JPEG2000 and H.264 coding compare between JPEG2000 and H.264 coding standardsstandardsMoreover, the test resolutions and characteristics of Moreover, the test resolutions and characteristics of input sequences are very limited input sequences are very limited JPEG2000 and H.264 are the latest image and video JPEG2000 and H.264 are the latest image and video coding standards, respectivelycoding standards, respectively

JPEG 2000JPEG 2000

JPEG 2000 standard JPEG 2000 standard

Material eXchange FormatMaterial eXchange Format

Open Archival Information System (OAIS) reference Open Archival Information System (OAIS) reference model model - - own system architectureown system architecture

CCommercial archivesommercial archives - - stock-shot licensing stock-shot licensing companies, newsreel and future collections, companies, newsreel and future collections, producers, and distributorsproducers, and distributors

PPublic film archivesublic film archives - - digitally projected cinema, digitally projected cinema, home video and home cinema, internet and home video and home cinema, internet and television distributiontelevision distribution

File formatsFile formatsTTwo different file formats to store image, audio and wo different file formats to store image, audio and metadatametadata Each is able to store archived items in the best Each is able to store archived items in the best possible quality and to facilitate the access to the possible quality and to facilitate the access to the archived items archived items SSet of “modules”, produced at different places and et of “modules”, produced at different places and for different purposesfor different purposes TTo create new metadata modules for different stuff, o create new metadata modules for different stuff, people and dealspeople and deals

JPEG-2000 coding techniqueJPEG-2000 coding technique

JPEG-2000JPEG-2000Low-complexity standards for lossless image Low-complexity standards for lossless image compression do not permit a control of the resulting bit-compression do not permit a control of the resulting bit-raterateThis is possible by using the wavelet based standard This is possible by using the wavelet based standard JPEG-2000, which allows for an embedded output bit JPEG-2000, which allows for an embedded output bit stream that can be truncated at a desired quality levelstream that can be truncated at a desired quality levelThe drawback is increased complexity and a slightly The drawback is increased complexity and a slightly worse performance for mathematically lossless worse performance for mathematically lossless compression compression JPEG-2000 is based upon a wavelet decomposition of JPEG-2000 is based upon a wavelet decomposition of the original image, with up to 5 wavelet decomposition the original image, with up to 5 wavelet decomposition levelslevels

JPEG-2000 coding techniqueJPEG-2000 coding technique

Each subband is divided into rectangular code-blocks, and Each subband is divided into rectangular code-blocks, and each code-block is independently coded by an arithmetic each code-block is independently coded by an arithmetic codec codec using progressive bit planesusing progressive bit planesThe bit stream is created by using a sophisticated The bit stream is created by using a sophisticated distortion minimization algorithm called EBCOT which gives, distortion minimization algorithm called EBCOT which gives, for each layer, the optimum contribution of each code blockfor each layer, the optimum contribution of each code blockReversible wavelet transforms were used, and the optional Reversible wavelet transforms were used, and the optional quantization was skipped quantization was skipped An intensive simulation campaign showed that no An intensive simulation campaign showed that no appreciable gain is seen after the second wavelet level, and appreciable gain is seen after the second wavelet level, and this level was taken as a reference this level was taken as a reference We finally noted that colour space conversions (RGB, We finally noted that colour space conversions (RGB, YUV, YCbCr, etc.) do not give any appreciable gain, so that YUV, YCbCr, etc.) do not give any appreciable gain, so that images were compressed directly in their original colour images were compressed directly in their original colour spacespace

Standardization for archival Standardization for archival applicationsapplications

TheThe requirements for archival applications: requirements for archival applications:open standard (ISO standard 15444-1: 2004)open standard (ISO standard 15444-1: 2004)

allows mathematically lossless as well as visually allows mathematically lossless as well as visually lossless compressionlossless compression

advantage of allowing a scalable presentation of advantage of allowing a scalable presentation of image dataimage data

compression is performed on an intraframe basis onlycompression is performed on an intraframe basis only

the use of wavelets and arithmetic entropy coding the use of wavelets and arithmetic entropy coding produces a hierarchical code streamproduces a hierarchical code stream,, allowing to allowing to encode images at the desired maximum resolution encode images at the desired maximum resolution and qualityand quality

Standardization for archival applications

Figure 2. General encoding structure for JPEG 2000

RATECONTROL

RGB toYCbCr

TRANSFORM

WAVELETTRANSFORM

QUANTI-ZATION

ENTROPYCODING

PACKETI-ZATION

FINALCODINGSTREAM

Standardization for archival Standardization for archival applicationsapplications

WWavelet-based image compression standardavelet-based image compression standard

TTo transform each colour component into a hierarchy o transform each colour component into a hierarchy of subbands of subbands

EEmbedded block coding with optimized truncationmbedded block coding with optimized truncation (EBCOT)(EBCOT)

CContext-adaptive arithmetic coding to efficiently ontext-adaptive arithmetic coding to efficiently

represent a collection of binary symbolsrepresent a collection of binary symbols

Bit rate and quality are the two primary optimization Bit rate and quality are the two primary optimization criteria for rate-controlcriteria for rate-control

Simulation resultsSimulation results

Digital cinemaDigital cinema is different in several fundamental ways is different in several fundamental ways from other applicationsfrom other applications

TThe resolution is higher, with a single frame of 4x10he resolution is higher, with a single frame of 4x1033 data containing approximately 8x10data containing approximately 8x1066 pixels pixels

TThe quality requirements are more stringenthe quality requirements are more stringent

CCinema viewers tend to sit within 1,5 to 3 screen inema viewers tend to sit within 1,5 to 3 screen heights of the projected image heights of the projected image

RRelative compression efficiency advantages for coding elative compression efficiency advantages for coding of digital cinema image sequences using JPEG 2000 of digital cinema image sequences using JPEG 2000 and H.264 standardsand H.264 standards

Simulation resultsSimulation results

The test content used was from the DCI (Digital Cinema The test content used was from the DCI (Digital Cinema Initiatives) Initiatives) mminimovie sequence “Confetti Title Screen” inimovie sequence “Confetti Title Screen”

RResolution of 4096x1714 (sequence 4K), with 12 bits per esolution of 4096x1714 (sequence 4K), with 12 bits per colour and 4:4:4 colour samplingcolour and 4:4:4 colour sampling

To reduce the amount of processing during the To reduce the amount of processing during the experiment, cropped region of size 512x208 (sequence experiment, cropped region of size 512x208 (sequence 512) was used512) was used a) JPEG 2000; a) JPEG 2000; b) H.264 in which every frame is an Ib) H.264 in which every frame is an I frame; frame; c) H.264 with an I frame of period 16, and with both B and P c) H.264 with an I frame of period 16, and with both B and P

frames used between the I framesframes used between the I frames

Simulation resultsSimulation results

Figure 3. PSNR versus bit rate for 4K sequence

Simulation resultsSimulation results

Figure 4. PSNR versus bit rate for 512 sequence

Conclusion Conclusion

Film is being replaced by digitally content and this Film is being replaced by digitally content and this lacks film’s noise affordable and more certain futurelacks film’s noise affordable and more certain future

PPractical solutionractical solution - - a system ready to be implemented a system ready to be implemented and as an overall approach and modeland as an overall approach and model

DC archive system is in its implementation pDC archive system is in its implementation phasehase

TTo meet the needs of archiving and distributing both o meet the needs of archiving and distributing both archival content and currentarchival content and current digital productionsdigital productions

DDigitized analogue film and video, digital video and igitized analogue film and video, digital video and digital cinema products digital cinema products -- to transcode them on demand to transcode them on demand for distribution for distribution