Dirac Coding: Lead Engineer BBC R&D BBC MMIX R&D

Transcription

1 Dirac Coding: Tutorial & Implementation ti Dr Tim Borer Lead Engineer BBC

2 What is Dirac? Dirac is a family of video codecs spanning mobile to UHDTV and film video post production. Think H264 for low bit rates Think JPEG2000 for high quality Royalty free open technology Simple, low cost Dirac Pro is Intra coding for professional & production use

3 The BBC s Role Technology development elopment and standardization BBC does not sell hardware or software Open Source Software. Non-exclusively licensed hardware implementations BBC return on investment through cost savings

4 History BBC led development, elopment started 2003 First software released March 2004 Specification published 2007 Version 1.0 software September 2008 HDTV compression demos at IBC 2008 on EBU Village Dirac Integrated into VLC Player 2008/2009

5 Dirac in VLC Media Player

6 Dirac Pro Intra frame coding for video production Wide range of applications from lossless HD to < 50Mbit/s Low complexity Simple software implementation Small hardware form factor Low energy Low cost Low Latency Non proprietary, royalty free, open technology

7 Flexible Features Any picture format QCIF to beyond UHDTV Any frame rate 4:2:0, 4:2:2, 4:4:4 & RGB Any bit depth (including 8, 10 & 12 bits) Progressive and Interlaced pictures Lossless coding 32 bit picture numbers

8 Dirac Pro compression model Wavelet Transform Coefficient Ordering Quantisation VLC Coding Arithmetic Coding

9 Dirac Pro Technology Wavelets (like JPEG2000) less blocking Uses lifting and integer implementation Stages of a wavelet transform

10 Lifting Implementation of (One Dimensional) Wavelet Transform

11 Dead Zone Quantiser c i, j c i, j, c 0 i, j q c i, j, c < 0 i, j q

12 Dirac Pro Technology Deterministic VLC interleaved exp- Bit sequence Decoded value Golomb Simple Low latency Supports high quality / high bit rates

13 Dirac ProTechnology Arithmetic Coding (optional) Optimized for simple parallel implementation and high bit rates

14 Binary arithmetic coding Z -1 Context modelling Probabilities Symbols Arithmetic coding engine Bits

15 Dirac Pro Profiles 3 Profiles currently defined Low Delay Profile Codes slices, no arithmetic coding Simple, low latency (<10ms), low compression Simple Profile Codes whole pictures, no arithmetic ti coding Higher compression, latency ~ 1 picture Main Profile Simple profile + arithmetic coding Higher compression, more complex, more latency

16 Low Delay Slices

17 Dirac Pro Slice Structure

18 Why No Arithmetic Coding? Low Delay and Simple Profiles don t use Arithmetic ti coding Little gain at low compression ratios Lossless coding coding gain about :1 compression coding gain about 3 Arithmetic coding very hardware intensive at high bit rates

19 Wavelet Transform

20 Wavelet Coefficient Ordering in Simple & Main Profiles

21 Compression Factor 2to8 Flavors of Dirac Low Core Long Latency Syntax Intra AC GOP lossless to lossless to up to 200+ Complexity low low medium high Coding Units slices pictures pictures access units (GOPs) Latency very low 1-2 pictures 2-3 pictures 2+ pictures Arithmetic Coding no no yes yes Motion Compensation no no no yes Application DP 1.5, 270, 221 over SDI contribution SDI / IP / ASI File based, archive tapeless, distribution

22 Dirac Bit Rates Low Core I t AC Lossless Intra AC Delay Syntax frame Inter- Long GOP Ratio 21 2:1 61 6:1 91 9:1 20:1 50:1 200:1 HDTV MBit/s SDTV MBit/s Notes Production Production Production Production Production Distribution quality quality quality quality quality quality Same as JPEG2000 Same as JPEG2000 Same as H264 Same as X264

23 Dirac Pro Hardware Implementations Dirac Pro 270 Multi-standard t d HD over 270MBit/s SD-SDI Dirac Pro P60 over 1.5G HD-SDI Dirac Pro HD Signals over single HD- SDI link Suitable for Stereoscopic 3D production

24 Studio Production

25 Dirac Pro Confidence Monitoring

26 Dirac Pro at the Olympics

27 Dirac Pro 270 Dirac Pro 270 allows HD over SD SDI links Dirac Pro provides a compatible SD picture Dirac Pro has low, 3ms, latency

28 Current Users BBC OB, Beijing Olympics ORF (Austrian national broadcaster) Asia Television Hong Kong Television i Broadcasts Limited it (TVB) Hong Kong. Rainbow Media New York Cambridge University for use in the HIPNet (Heterogenous IP Networks) project in association with Essex University

29 BBC Raman Network The Raman Network 10Gb/s DWDM system

30 BBC Media City Salford Quays, Manchester, UK

31 Dirac over ASI &IP Using Dirac Low Delay and Core Syntax with and without arithmetic coding HD and SD compression Variable Bit rates Bit rates below 50Mbit/s (HD), 10MBit/s SD MPEG-2 TS encapsulation SMPTE 2022 (Pro-MPEG COP3) RTP, FEC compatible with existing equipment

32 Cascaded Coding

33 Cascaded Coding Multigeneration Coding Loss db st 2nd 3rd 4th 5th 6th 7th 8th Coding Generations Dirac Pro 270 Dirac Pro 1.5

34 Standarisation Dirac Pro is being standardised with the SMPTE. Standardisation is virtually complete SMPTE (VC-2) Codec & bit stream specification SMPTE Specifies Coding Levels

35 Dirac Pro Conformance SMPTE Specifies VC-2 Conformance Over 6000 conformance test sequences Available, pre-standard, at k/d d/ streams Reference decoder and stream generator available

36 Dirac Pro Standards Documents Described in SMPTE Engineering Guidline

37 Dirac Pro Application Specifications SMPTE RP 2047 (Dirac Pro 1.5) VC-2 Mezzanine Level Compression of 1080P High Definition Video Sources SMPTE 2047 Transport of VC-2 Compressed Video over HD-SDI HD over 270MBit/s SD SDI Dirac Pro 270 Video over ASI and IP

38 Related Specifications Encapsulation in MPEG-TS (ISO/IEC Registered with SMPTE Supports transport t of Dirac Pro over ASI Supports transport of Dirac Pro over IP using Pro MPEG COP#3 (SMPTE 2022) Encapsulation in Quicktime,.mov files (ISO/IEC )

39 Engineering Guildlines Many codec standards Many incompatible, standards based, solutions available Guidelines and Recommended practice needed!

40 Summary Dirac Pro competes with JPEG2000 and AVC-I Transport over SDI, ASI and IP Low Latency Low complexity Low cost, small form factor, low energy Flexible SMPTE Standard (nearly!)

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42 3.2 Stream structure A Dirac stream is a concatenation of Dirac sequences: Sequence

43 Dirac sequences A Dirac sequence ence corresponds to video with constant video parameters. A Dirac sequence has Parse Info headers for navigation and synchronisation, and Data Units which include all the pictures: Parse Info Sequence Header Parse Info Data Unit Parse Info

44 Navigation Parse Info headers form a doubly-linked linked list: can jump from one data unit to another without parsing it Dirac pictures contain true picture numbers