Audio Systems for DTV

Transcription

1 Audio Systems for TV ITU Seminar Kiev, Nov. 14, 2000 Tony Spath olby Laboratories England

2 on t forget the audio 2

3 "The cost of entertainment, at least as far as the hardware is concerned, is falling: inexpensive chip-sets, lower-cost flatscreen televisions, free or inexpensive set-top boxes, and not forgetting olby 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 IGITAL TELEVISION by Chris Forrester Page 7, chapter 1 3

4 UK Household Penetration Widescreen vs olby Surround 18.00% 16.00% 14.00% 12.00% 10.00% 8.00% 6.00% 4.00% 2.00% 0.00% 17.90% 15.20% 4.90% 1.70% Widescreen Surround Source: Understanding & Solutions 4

5 Audio - mono beginnings TV Mono Audio 5

6 Stereo - rather better L R NICAM TV Stereo Audio Track 6

7 olby Surround - Matrix audio L C R Stand-alone or built in to TVs Pro Logic ecoder Stereo Audio Track S S 7

8 5.1 discrete audio L C R Sub (the.1 ) igital Bit Stream olby igital ecoder Ls Stand-alone or built in to TVs Rs 8

9 5.1 audio is important Surround sound has become very popular ITU-R R Rec. BS All new media support 5.1 ch audio Movies in the cinema igital Terrestrial TV V-V V and V-A igital Cable TV igital Satellite TV 9

10 The audio systems for TV: MPEG-1,2 Layer II VB olby igital (technical name: AC-3 ) ATSC VB MPEG-2 2 AAC ISB 10

11 Common attributes of all of these audio coders Significant reduction of bit rate compared to PCM audio compression factors of to 12-1 Can be used for mono, 2ch stereo, 5.1 ch Internationally standardized by ISO/IEC or ITU-R Open specification and availability of patent license 11

12 ifferences between coders Efficiency (quality vs bit-rate) Consumer features to improve audio service Level control ynamic range control own-mixing Cost Adoption by significant applications Marketplace success Technology support 12

13 MPEG-1 Layer II Technology MPEG-1 1 Standard Mono, 2ch stereo audio ITU-R R Recommendation BS.1115 (2 ch) Originally developed as coding system for digital radio Eureka 147 (became AB) Basic 2 channel delivery pipe Capability to carry aux data No consumer features included 13

14 MPEG-2 Layer II Technology MPEG-2 2 Standard includes 5.1 surround ITU-R R Recommendation BS.1196 MPEG reacted to olby announcement of 5.1ch AC-3 MPEG-2 2 is MPEG-1 1 stereo plus a BC (backward compatible) extension to provide extra channels MPEG-2 2 audio frame (should be >/=640 kbit/s for broadcast quality) MPEG-1 stereo audio With With transmissions this this will will be be a mix mix of of L,C,R, Ls,Rs. Stereo IRs will will only only decode this this portion Ls,C,Rs and LFE elements These need need to to be be re-matrixed in in a decoder with with the the MPEG-1 portion to to derive separate L & R channels 14

15 MPEG-2 Layer II Technology MPEG-2 2 Standard ITU-R R Recommendation BS.1196 MPEG reacted to olby announcement of 5.1ch AC-3 MPEG-2 2 is MPEG-1 1 stereo plus a BC (backward compatible) extension to provide extra channels Technical deficiencies due to BC requirement Higher bit rate needed for 5.1 chs 15

16 MPEG Layer II Adoption Basic in VB system (MPEG-1 1 2ch) Employed in VC (MPEG-1 1 2ch) Specified for PAL V but then rejected (MPEG ch) Widely applied for mono, 2ch stereo market failure for 5.1 ch Significant 2ch presence in marketplace but not visible to consumers 16

17 olby igital (AC-3) Technology ATSC Standard A/52 esigned specifically to carry any audio Mono, stereo, surround, 5.1 Consumer features designed in to improve audio service ITU-R R Recommendation BS.1196 esigned to balance cost / complexity / performance Key to early and widespread market acceptance 17

18 olby AC-3 Adoption Basic in ATSC system Also in U.S. CATV, BS Employed in V (worldwide) Used in computer gaming platforms for mono, 2ch stereo, 5.1 ch audio Option in VB (ETR-154 Annex C) Selected by Australia, Singapore, etc. Substantial and growing presence in home video marketplace ominant system for 5.1 ch Highly visible to consumers P 18

19 V the PAL format that nearly wasn t Compromise standard NTSC 525/60 disc use AC-3 3 (like ATSC) PAL 625/50 disc use Layer II (like VB) Unsuccessful launch of PAL 625/50 format Lack of support for MPEG-2 2 audio Poor performance of MPEG-2 2 audio Standard changed so AC-3 could be used in all discs Marketplace decision which to use on PAL 625/50 discs 19

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22 olby igital in VB Panasonic ad for German broadcaster ProSieben 22

23 MPEG-2 AAC Technology MPEG-2 2 standard (part 7) eveloped after olby, AT&T showed that non-bc codecs could offer higher performance than the BC Layer II standard Main contributions from 4 partners AT&T, olby, Frauenhofer,, Sony olby administers the patent licensing Higher performance & complexity than other codecs 23

24 MPEG-2 AAC Adoption Basic in ISB system Employed in internet audio, solid state audio players, some digital radio Used for mono, 2ch stereo not yet applied to 5.1 ch Growing presence in music delivery marketplace But no presence in home video (yet?) 24

25 Audio Quality (CRC test) 25

26 Bit rate for high quality 5.1 ch MPEG-2 2 Layer II 640 kb/s 448 kb/s (average - with variable bit rate) no significant commercial usage olby igital (AC-3) kb/s extensive usage in V, L, TV MPEG-2 2 AAC 320 kb/s no commercial usage (yet) 26

27 Important Consumer Features Level control in the decoder Achieve uniform loudness / Avoid level changes: between program segments between channels, signal sources ynamic range control Capability to deliver both: wide dynamic range for audio enthusiast narrow dynamic range for general listeners ownmixing Serve mono, 2 ch and 5.1 ch listeners with the same bit stream 27

28 Typical audio signals 0 dbfs ACTION MOVIE RAMA SPORTS SYMPHONY ROCK NEWS -10 dbfs -20 dbfs -30 dbfs -40 dbfs AVERAGE IALOG SIGNAL PEAKS 28

29 How we broadcast audio today 0 dbfs ACTION MOVIE RAMA SPORTS SYMPHONY ROCK NEWS -10 dbfs -20 dbfs -30 dbfs -40 dbfs AVERAGE / IALOG SIGNAL PEAKS 29

30 Typical audio signals 0 dbfs -10 dbfs ACTION MOVIE RAMA SPORTS SYMPHONY ROCK NEWS dbfs -30 dbfs dbfs AVERAGE IALOG SIGNAL PEAKS 30

31 Normalized audio signals 0 dbfs ACTION MOVIE RAMA SPORTS SYMPHONY ROCK NEWS -10 dbfs -20 dbfs -30 dbfs -40 dbfs AVERAGE IALOG SIGNAL PEAKS 31

32 ynamic range control dbfs 0 Original Signal Hi Fi Stereo Reproduction Mono TV Reproduction HIGH LEVEL YNAMICS LOW LEVEL YNAMICS

33 ownmixing Optimize downmix at decoder Mono compatible Surround compatible Match level between 2ch and 5.1 ch content Avoid clipping / overload of downmix 14 db buildup in level of mono downmix! 33

34 ownmixing: One Bit-stream for all OLBY IGITAL ENCOER V TERRESTRIAL CABLE SATELLITE A SINGLE BITSTREAM ELIVERE TO MANY RECEIVERS SET-TOP BOX IGITAL PASS THROUGH Lt / Rt OWNMIX STEREO OWNMIX IGITAL HOME THEATER 5.1 ISCRETE HOME THEATER PRO LOGIC HI-FI VCR STEREO, HEAPHONES MONO OWNMIX TV RF REMO 34

35 Implementation Status of Consumer Features olby igital (AC-3) First system designed to include these features Universal implementation MPEG Layer II olby igital feature set recently copied and documented in ETR-154 Annex Negligible implementation MPEG-2 2 AAC Some specifications to enable in specification Negligible implementation No coordinating entity to ensure consistency 35

36 Licensing for MPEG Layer II Layer II Basic patent only license for CE manufacturers No support with know-how 36

37 Licensing for AC-3 Patent plus know-how license for CE manufacturers. No royalty on IC s Reference code provided Comprehensive design manual Extensive support of licensees Support during design phase Test and verification of all product models Visit licensees twice per year 37

38 Licensing for AAC Basic patent-only license issued by olby For patents owned by AT&T, olby, Frauenhofer,, Sony Know-how can be purchased for an extra charge olby will offer a know-how package olby support for AAC will not be as extensive as olby support for AC-3 ue to relative market sizes 38

39 License fees - 2ch product US $ Low Med High CE Company Sales Volume Layer II (patent) AC-3 (patent+knowhow) AAC (patent) 39

40 License fees - 5.1ch product US $ Low Med High CE Company Sales Volume Layer II (patent) AC-3 (patent+knowhow) AAC (patent) 40

41 olby igital Marketplace olby igital Units (Cumulative) 2 channel Radio 2-channel TV 5-channel TV V-Video units V-ROM units 5.1 channel units 70,000,000 60,000,000 50,000,000 40,000,000 30,000,000 20,000,000 10,000, /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 41

42 olby igital at home Set Top Box V Player TV Set Gaming Platform olby igital ecoder + 6 channel amp Common Interconnect: IEC

43 Growth in 5.1 ch olby igital A/V Receivers - Cumulative Millions AC-3 Layer II AAC (est) 43

44 V players with olby igital 44

45 Full 5.1 ch olby igital receiver 45

46 olby igital in a box 46

47 Major considerations for selection of audio coding for TV 5.1 channel audio is very important - the future of audio is surround AAC and AC-3 3 score better than MPEG LII Based on technical attributes and market success Compatibility with other 5.1 ch media (V) AC-3 3 scores best MPEG Layer II has failed in 5.1 AAC -???? (perhaps) 47

48 Is AAC a viable 5.1 ch solution? Only current likely application for 5.1 ch AAC is ISB in Japan The market for 5.1 ch AAC products must be substantial before AAC is well supported Limited application areas of 5.1 ch AAC Subset of any market uses 5.1 ch vs 2ch Unclear if 5.1ch AAC will reach critical mass olby will provide some support for AAC 5.1 ch but much less than the support we give AC-3 3 (due to relative market sizes and generated revenue) 48

49 Logical Conclusions AAC is the best technical solution Coding efficiency AC-3 3 offers best balance of all factors Cost Complexity Support Interoperability Consumer recognition and acceptance 49

50 Audio in TV Systems ATSC olby igital (AC-3) is sole audio solution VB Layer II 2ch stereo mandated Option to include AC-3 ISB AAC mandated Could be modified to include AC-3 3 as alternative 50

51 Conclusions and Recommendations A TV system should be able to offer 5.1 ch audio (even if transmissions start with stereo or mono) From a 5.1 ch audio viewpoint: ATSC with AC-3 3 is a solid choice VB with the AC-3 3 option is a solid choice Important to mandate this option in all receivers to avoid wasting bits on MPEG-1 1 simulcast ISB with AAC is a unknown Risk could be eliminated by specifying ISB with AC-3 51

52 on t forget the audio 52

53 Audio Systems for TV Thank You Tony Spath olby Laboratories England