Audio Systems for DTV ITU Seminar Kiev, Nov. 14, 2000 Tony Spath Dolby Laboratories England [email protected] http://www.dolby.com D Don’t forget the audio D 2 "The cost of entertainment, at least as far as the hardware is concerned, is falling: inexpensive chip-sets, lower-cost flat- screen televisions, free or inexpensive set-top boxes, and not forgetting Dolby multi-channel surround sound (said by more than a few experts to have been responsible for selling more large-screen televisions that any other technological advance since colour)." THE BUSINESS OF DIGITAL TELEVISION by Chris Forrester Page 7, chapter 1 http://www.bh.com/bookscat/samples/0240516060/0240516060.pdf D 3 UK Household Penetration Widescreen vs Dolby Surround 17.90% 18.00% 16.00% 15.20% 14.00% 12.00% 10.00% Widescreen 8.00% Surround 6.00% 4.90% 4.00% 1.70% 2.00% 0.00% 1998 1999 Source: Understanding & Solutions D 4 Audio - mono beginnings TV Mono Audio D 5 Stereo - rather better L R Stereo NICAM TV Audio Track D 6 Dolby Surround - Matrix audio L C R Stand-alone Pro Logic Stereo or built in to Decoder Audio TVs Track S S D 7 5.1 discrete audio L C R Sub (the“.1”) Digital Dolby Digital Bit Stream Decoder Ls Stand-alone Rs or built in to TVs D 8 “5.1” audio is important n Surround sound has become very popular n ITU-R Rec. BS.775-1 n All new media support 5.1 ch audio uMovies in the cinema uDigital Terrestrial TV uDVD-V and DVD-A uDigital Cable TV uDigital Satellite TV D 9 The audio systems for DTV: n MPEG-1,2 Layer II uDVB n Dolby Digital (technical name: “AC-3”) uATSC uDVB n MPEG-2 AAC uISDB D 10 Common attributes of all of these audio coders n Significant reduction of bit rate compared to PCM audio ucompression factors of 6-1 to 12-1 n Can be used for mono, 2ch stereo, 5.1 ch n Internationally standardized by ISO/IEC or ITU-R n Open specification and availability of patent license D 11 Differences between coders n Efficiency (quality vs bit-rate) n Consumer features to improve audio service uLevel control uDynamic range control uDown-mixing n Cost n Adoption by significant applications n Marketplace success n Technology support D 12 MPEG-1 Layer II Technology n MPEG-1 Standard uMono, 2ch stereo audio n ITU-R Recommendation BS.1115 (2 ch) n Originally developed as coding system for digital radio uEureka 147 (became DAB) uBasic 2 channel delivery pipe uCapability to carry aux data uNo consumer features included D 13 MPEG-2 Layer II Technology n MPEG-2 Standard – includes 5.1 surround n ITU-R Recommendation BS.1196 n MPEG reacted to Dolby announcement of 5.1ch AC-3 u MPEG-2 is MPEG-1 stereo plus a BC (backward compatible) extension to provide extra channels MPEG-2 audio frame (should be >/=640 kbit/s for broadcast quality) MPEGMPEG--11 stereostereo audioaudio Ls,C,Ls,C,RsRsandand LFELFE elementselements WithWith 5.1 5.1 transmissions transmissions this this will will be be TheseThese need need to to be be re re--matrixedmatrixedinin a a 5.1 5.1 aa mix mix of of L,C,R, L,C,R, Ls, Ls,RsRs. Stereo Stereo decoderdecoder with with the the MPEG MPEG--11 portion portion to to IRDsIRDs will will only only decode decode this this portion portion derivederive separate separate L L & & R R channels channels D 14 MPEG-2 Layer II Technology n MPEG-2 Standard n ITU-R Recommendation BS.1196 n MPEG reacted to Dolby announcement of 5.1ch AC-3 u MPEG-2 is MPEG-1 stereo plus a BC (backward compatible) extension to provide extra channels n Technical deficiencies due to BC requirement u Higher bit rate needed for 5.1 chs D 15 MPEG Layer II Adoption n Basic in DVB system (MPEG-1 2ch) n Employed in VCD (MPEG-1 2ch) n Specified for PAL DVD but then rejected (MPEG-2 5.1ch) n Widely applied for mono, 2ch stereo umarket failure for 5.1 ch n Significant 2ch presence in marketplace ubut not visible to consumers D 16 Dolby Digital (AC-3) Technology n ATSC Standard A/52 n Designed specifically to carry any audio u Mono, stereo, surround, 5.1 u Consumer features designed in to improve audio service n ITU-R Recommendation BS.1196 n Designed to balance cost / complexity / performance u Key to early and widespread market acceptance D 17 Dolby AC-3 Adoption n Basic in ATSC system u Also in U.S. CATV, DBS n Employed in DVD (worldwide) n Used in computer gaming platforms n … for mono, 2ch stereo, 5.1 ch audio n Option in DVB (ETR-154 Annex C) u Selected by Australia, Singapore, etc. n Substantial and growing presence in home video marketplace uDominant system for 5.1 ch PPP uHighly visible to consumers D 18 DVD – the PAL format that nearly wasn’t n Compromise standard uNTSC 525/60 disc use AC-3 (like ATSC) uPAL 625/50 disc use Layer II (like DVB) n Unsuccessful launch of PAL 625/50 format uLack of support for MPEG-2 audio uPoor performance of MPEG-2 audio n Standard changed so AC-3 could be used in all discs uMarketplace decision which to use on PAL 625/50 discs 19 D D 20 D 21 Dolby Digital in DVB Panasonic ad for German broadcaster ProSieben D 22 MPEG-2 AAC Technology n MPEG-2 standard (part 7) n Developed after Dolby, AT&T showed that non-BC codecs could offer higher performance than the BC Layer II standard n Main contributions from 4 partners F AT&T, Dolby, Frauenhofer, Sony F Dolby administers the patent licensing n Higher performance & complexity than other codecs D 23 MPEG-2 AAC Adoption n Basic in ISDB system n Employed in internet audio, solid state audio players, some digital radio n Used for mono, 2ch stereo unot yet applied to 5.1 ch n Growing presence in music delivery marketplace uBut no presence in home video (yet?) D 24 Audio Quality (CRC test) D 25 Bit rate for high quality 5.1 ch n MPEG-2 Layer II u 640 kb/s u 448 kb/s (average - with variable bit rate) u no significant commercial usage n Dolby Digital (AC-3) u 384 - 448 kb/s u extensive usage in DVD, LD, DTV n MPEG-2 AAC u 320 kb/s u no commercial usage (yet) D 26 Important Consumer Features n Level control in the decoder u Achieve uniform loudness / Avoid level changes: F between program segments F between channels, signal sources n Dynamic range control u Capability to deliver both: F wide dynamic range for audio enthusiast F narrow dynamic range for general listeners n Downmixing u Serve mono, 2 ch and 5.1 ch listeners with the same bit stream D 27 Typical audio signals ACTION DRAMA SPORTS SYMPHONY ROCK NEWS MOVIE 0 dBFS -10 dBFS -20 dBFS -30 dBFS -40 dBFS AVERAGE DIALOG SIGNAL PEAKS D 28 How we broadcast audio today ACTION DRAMA SPORTS SYMPHONY ROCK NEWS MOVIE 0 dBFS -10 dBFS -20 dBFS -30 dBFS -40 dBFS AVERAGE / DIALOG SIGNAL PEAKS D 29 Typical audio signals ACTION DRAMA SPORTS SYMPHONY ROCK NEWS MOVIE 0 dBFS -10 dBFS 10 -20 dBFS 21 20 20 27 24 -30 dBFS -40 dBFS AVERAGE DIALOG SIGNAL PEAKS D 30 Normalized audio signals ACTION DRAMA SPORTS SYMPHONY ROCK NEWS MOVIE 0 dBFS -10 dBFS -20 dBFS -30 dBFS -40 dBFS AVERAGE DIALOG SIGNAL PEAKS D 31 Dynamic range control Original Hi Fi Stereo Mono TV dBFS Signal Reproduction Reproduction 0 -10 HIGH LEVEL -20 DYNAMICS -30 -40 -50 LOW LEVEL DYNAMICS -60 -70 -80 D 32 Downmixing n Optimize downmix at decoder uMono compatible uSurround compatible n Match level between 2ch and 5.1 ch content n Avoid clipping / overload of downmix u14 dB buildup in level of mono downmix! D 33 Downmixing: One Bit-stream for all DIGITAL SET-TOP BOX HOME THEATER DVD DIGITAL 5.1 TERRESTRIAL PASS DISCRETE CABLE THROUGH SATELLITE HOME THEATER Lt / Rt PRO A SINGLE DOLBY DOWNMIX LOGIC DOLBY BITSTREAM DIGITAL DIGITAL DELIVERED ENCODER HI-FI VCR ENCODER TO MANY RECEIVERS STEREO STEREO, DOWNMIX HEADPHONES MONO TV RF REMOD DOWNMIX D 34 Implementation Status of Consumer Features n Dolby Digital (AC-3) u First system designed to include these features u Universal implementation n MPEG Layer II u Dolby Digital feature set recently copied and documented in ETR-154 Annex D u Negligible implementation n MPEG-2 AAC u Some specifications to enable in specification u Negligible implementation u No coordinating entity to ensure consistency D 35 Licensing for MPEG Layer II n Layer II uBasic patent only license for CE manufacturers uNo support with know-how D 36 Licensing for AC-3 n Patent plus know-how license for CE manufacturers. uNo royalty on IC’s uReference code provided uComprehensive design manual n Extensive support of licensees uSupport during design phase uTest and verification of all product models uVisit licensees twice per year D 37 Licensing for AAC n Basic patent-only license issued by Dolby uFor patents owned by AT&T, Dolby, Frauenhofer, Sony n Know-how can be purchased for an extra charge uDolby will offer a know-how package uDolby support for AAC will not be as extensive as Dolby support for AC-3 F Due to relative market sizes D 38 License fees - 2ch product US $ CE Company Sales Volume 1.2 1 0.8 0.6 0.4 0.2 0 Low Med High Layer II (patent) AC-3 (patent+knowhow) AAC (patent) D 39 License fees - 5.1ch product US $ CE Company Sales Volume 2.5 2 1.5 1 0.5 0 Low Med High Layer II (patent) AC-3 (patent+knowhow) AAC (patent) D 40 Dolby Digital Marketplace Dolby Digital Units (Cumulative) 70,000,000 2 channel Radio 60,000,000 2-channel TV 5-channel TV 50,000,000 DVD-Video units DVD-ROM units 40,000,000 5.1 channel units 30,000,000 20,000,000 10,000,000 0 1/96 2/96 3/96 4/96 1/97 2/97 3/97 4/97 1/98 2/98 3/98 4/98 1/99 2/99 3/99 4/99 1/00 D 41 Dolby Digital at home GamingGaming SetSet TopTop BoxBox DVDDVD PlayerPlayer DTVDTV SetSet PlatformPlatform CommonCommon Interconnect:Interconnect: IEC61937 DolbyDolby DigitalDigital IEC61937 DecoderDecoder ++ 66 channelchannel ampamp D 42 Growth in 5.1 ch Dolby Digital A/V Receivers