Dolby Issue 3
Dolby Laboatoies, Inc Copoate Headquates Dolby Laboatoies, Inc. 100 Poteo Avenue San Fancisco, CA 94103-4813 USA Telephone 415-558-0200 Fax 415-863-1373 www.dolby.com Euopean Headquates Dolby Laboatoies, Inc. Wootton Bassett Wiltshie SN4 8QJ England Telephone (44) 1793-842100 Fax (44) 1793-842101 Dolby, Po Logic, and the double-d symbol ae egisteed tademaks of Dolby Laboatoies. Suound EX is a tademak of Dolby Laboatoies. Issue 3 2005 Dolby Laboatoies, Inc. All ights eseved. S05/14660/16797
Dolby Laboatoies, Inc. A Guide to Dolby Metadata Metadata povides unpecedented capability fo content poduces to delive the highest quality audio to consumes in a ange of listening envionments. It also povides choices that allow consumes to adjust thei settings to best suit thei listening envionments. In this document, we fist discuss the concept of metadata: Metadata oveview We then discuss the thee factos contolled by metadata that most diectly affect the consume s expeience: Dialogue level Dynamic ange contol (DRC) Downmixing Finally, we define each of the adjustable paametes, and povide sample combinations: Individual paametes Metadata combinations 1 Metadata Oveview Dolby Digital and Dolby E ae both data-ate eduction technologies that use metadata. Metadata is caied in the Dolby Digital o Dolby E bitsteam, descibing the encoded audio and conveying infomation that pecisely contols downsteam encodes and decodes. In nomal opeation, the encoded audio and metadata ae caied togethe as a data steam on two egula digital audio channels (AES3, AES/EBU, o S/PDIF). Metadata can also be caied as a seial data steam between Dolby E and/o Dolby Digital equipment. Metadata allows content povides unpecedented contol ove how oiginal pogam mateial is epoduced in the home. Dolby Digital is a tansmission bitsteam (sometimes called an emission bitsteam) intended fo delivey to the consume at home though a medium such as DTV o DVD. It consists of a single encoded pogam of up to six channels of audio descibed by one metadata steam. The consume s Dolby Digital decode epoduces the pogam audio accoding to the metadata paametes set by the pogam ceato, and accoding to settings fo speake configuation, bass management, and dynamic ange that ae chosen by the consume to match his specific home theate equipment and envionmental conditions. 1
Dolby Laboatoies, Inc. Dolby E is a distibution bitsteam capable of caying up to eight channels of encoded audio and metadata. The numbe of pogams anges fom one single pogam (Pogam Config: 5.1) to eight individual pogams on a single Dolby E steam (Pogam Config: 8 1). Each pogam is discete, with its own metadata in the Dolby E steam. Some metadata paametes in a Dolby E steam automatically configue a Dolby Digital encode at the point of tansmission, while othes affect only the consume s Dolby Digital decode opeation. Dolby E is a pofessional technology used fo boadcast applications, such as pogam oigination and distibution; the Dolby E bitsteam caies the entie metadata paamete set. Dolby Digital, used fo consume applications, such as tansmission to the home o fo DVD authoing, employs a subset of the full metadata paamete set called Dolby Digital metadata; the Dolby Digital bitsteam caies only those paametes necessay fo pope decoding by the consume. Metadata is fist inseted duing pogam ceation o masteing, and is caied though tansmission in a boadcast application o diectly onto a DVD. The metadata povides contol ove how the encoded bitsteam is teated at each step on the way to the consume s decode. Hee s an example of how it woks: In a boadcast tuck paked outside a football stadium, the pogam mixe chooses the appopiate metadata fo the audio pogam being ceated. The esulting audio pogam, togethe with metadata, is encoded as Dolby E and sent to the television station via fibe, micowave, o othe tansmission link. At the eceiving end of this tansmission, the Dolby E steam is decoded back to baseband audio and metadata. The audio pogam and the metadata ae monitoed, alteed, o e-ceated as othe elements of the pogam ae added in pepaation fo boadcast. This new audio pogam/metadata pai, eencoded as Dolby E, leaves the postpoduction studio and passes though the television station to Maste Contol, whee many incoming Dolby E steams ae once again decoded back to thei individual baseband digital audio/metadata pogams. The audio pogam/metadata pai that is selected to ai is sent to the tansmission Dolby Digital encode, which encodes the incoming audio pogam accoding to the metadata steam associated with it, theeby simplifying the tansmission pocess. Finally, the Dolby Digital signal is decoded in the consume s home, with metadata poviding the infomation fo that decoding pocess. Though the use of metadata, the mixe in the tuck has been able to contol the home decode fo the spoting event, while segments such as news beaks, commecials, and station IDs ae similaly decoded, each using metadata caied within each individual segment. This contol, howeve, equies the poduce to set the metadata paametes coectly, since they affect impotant aspects of the audio and can seiously compomise the final poduct if set impopely. Although most metadata paametes ae tanspaent to consumes, cetain paametes affect the output of a home decode, such as downmixing fo a specific speake configuation, o when the consume chooses Dynamic Range Contol to avoid distubing family and neighbos. 2
Dolby Laboatoies, Inc. Figue 1 shows a 5.1 + 2 Pogam Config, consisting of a 5.1-channel pogam and a two-channel seconday audio pogam (SAP). Pogam Souce 5.1-Channel Pogam Two-Channel (Steeo) Pogam Multichannel Monito System DP570 Multichannel Audio Tool in 5.1+2 Pogam Config Metadata L/R C/LFE Ls/Rs Lt/Rt DP571 Dolby E Encode in 5.1+2 Pogam Config The Dolby E bitsteam contains both the 5.1- and two-channel pogams encoded audio, and each pogam's metadata. Distibution Decoded Dolby E bitsteam delives both the 5.1- and two-channel pogams encoded audio along with coesponding metadata. The Dolby Digital bitsteam contains a single pogam s encoded audio and coesponding metadata. DP572 Dolby E Decode Metadata DP569 Dolby Digital Encode SAP o Visual Desciptive Dolby Two- Channel Encode Boadcast Cable, Satellite, o Teestial Consume Figue 1 Metadata Flow fom Poduction to Consume In the simplest tems, thee ae two functional classifications of metadata: Pofessional: These paametes ae caied only in the Dolby E bitsteam. They ae used to automatically configue a downsteam Dolby Digital encode, allowing maximum contol by the content poduce ove how the encoded bitsteam is teated at each step on the way to the consume s decode. Consume: These paametes ae caied in both the Dolby E and the Dolby Digital bitsteam. The consume s Dolby Digital decode uses these paametes to ceate the best possible audio pogam possible on each consume s playback system. Consume paametes include the DRC values, which ae ultimately enabled by the end use s selection, as discussed in Section 3, Dynamic Range Contol. 3
Dolby Laboatoies, Inc. Both types of metadata can be examined, modified, o passed though duing encoding. Table 1 lists the active metadata paametes and indicates whethe the paamete is Pofessional o Consume. Table 1 Metadata Paametes Extended Bitsteam Infomation paametes ae in italics. Metadata Paamete Pofessional Consume Pogam Configuation Pogam Desciption Text Dialogue Level Channel Mode LFE Channel Bitsteam Mode Line Mode Compession RF Mode Compession RF Ovemodulation Potection Cente Downmix Level Suound Downmix Level Dolby Suound Mode Audio Poduction Infomation Mix Level Room Type Copyight Bit Oiginal Bitsteam Pefeed Steeo Downmix Lt/Rt Cente Downmix Level Lt/Rt Suound Downmix Level Lo/Ro Cente Downmix Level Lo/Ro Suound Downmix Level Dolby Suound EX Mode A/D Convete Type DC Filte Lowpass Filte LFE Lowpass Filte Suound 3 db Attenuation Suound Phase Shift Special Paametes Thee ae othe pofessional paametes included in the Dolby E bitsteam that ae not unde diect use contol, such as Timecode and Pitch Shift. 4
Dolby Laboatoies, Inc. Timecode Dolby E bitsteams cay timecode infomation in hous:minutes:seconds:fames fomat. Pitch Shift The Pitch Shift paamete can be geneated automatically by a Dolby E decode to contol the Dolby Model 585 Time Scaling Pocesso. If the input to the Dolby E decode is not at nomal play speed (as with vaispeed o pogam play), then the Pitch Shift Code paamete indicates the amount of audio pitch shifting equied to estoe the oiginal pogam pitch. 2 Dialogue Level Dialogue Level (also known as dialogue nomalization o dialnom) is pehaps the single most impotant metadata paamete. The Dialogue Level setting epesents the long-tem A-weighted aveage level of dialogue within a pesentation, Leq(A). This level can be quantified with the Dolby Model LM100 Boadcast Loudness Mete. When eceived at the consume s Dolby Digital decode, this paamete setting detemines a level shift in the decode that sets, o nomalizes, the aveage audio output of the decode to a peset level. This aids in matching audio volume between pogam souces. In boadcast tansmission, the pope setting of Dialogue Level ensues that the consume eceives a standad listening level, so switching channels o watching a television pogam though the commecial beaks doesn t equie adjusting the volume. Using the same standad fo all content, whethe conveyed by boadcast television, DVD, o othe media, enables the consume to switch between souces and pogams while maintaining a comfotable and consistent listening level. The pope setting of the Dialogue Level paamete also enables the Dynamic Range Contol pofiles chosen by the content poduce to wok as intended in less-thanoptimal listening envionments, and is essential in any content poduction, whethe it is fo tansmission in a boadcast steam o fo diect distibution to consumes, as with DVDs. Note: Pogams without dialogue, such as an all-music pogam, still equie a caeful setting of the Dialogue Level paamete. When setting the paamete fo such content, it is useful to compae the pogam to the level of othe pogams. The goal is to allow the consume to switch to you pogam without having to adjust the volume contol. 5
Dolby Laboatoies, Inc. The Scale The scale used in the Dialogue Level setting anges in 1 db steps fom 1 to 31 db. Contay to what you might assume at fist, a setting of 31 epesents no level shift in the consume s decode, and 1 epesents the maximum level shift. Hee s why: Dolby Digital consume decodes nomalize the aveage output level that is, the output level aveaged ove time using the equivalent loudness method, Leq(A) to 31 dbfs (31 db below 0 db full-scale digital output) by applying a shift in level based on the Dialogue Level paamete setting. Note: The 31 dbfs Leq(A) should not be confused with the station efeence level (often 18 o 20 dbfs). It is common to have diffeent Leq(A) values fo pogam mateial that has the same efeence level. An aveage loudness level of 31 dbfs Leq(A) is quite compatible with facilities unning at a vaiety of efeence levels. When a decode eceives an input signal with a Dialogue Level setting of 31, it applies no level shift to the signal because this indicates to the decode that the signal aleady matches the taget level and theefoe equies no shift. In contast, a loude pogam equies a shift to match the 31 db standad. When the Dialogue Level paamete setting is 21, the decode applies a 10 db level shift to the signal. When the setting is 11, it applies a 20 db level shift, and so on. A Simple Rule: 31 + (dialogue level value) = Shift applied Example: 31 + ( 21) = 10 db The most impotant point to emembe is that in setting the Dialogue Level paamete, you ae poviding you listene with an essential sevice. Fo you listenes, setting this level popely means: The volume level is consistent with othe pogams. The DRC pofiles you make available to them wok as you intend. Once dialogue level is set, you can set up DRC pofiles to futhe benefit the consume. 3 Dynamic Range Contol Diffeent home listening envionments pesent a wide ange of equiements fo dynamic ange. Rathe than simply compessing the audio pogam at the tansmission souce to wok well in the pooest listening envionments, Dolby Digital encodes calculate and send Dynamic Range Contol (DRC) metadata with the signal. 6
Dolby Laboatoies, Inc. This metadata can then be applied to the signal by the decode to educe the signal s dynamic ange. Though the pope setting of DRC pofiles duing the masteing pocess, the content poduce can povide the best possible pesentation of pogam content in vitually any listening envionment, egadless of the quality of the equipment, numbe of channels, o ambient noise level in the consume s home. Many Dolby Digital decodes offe the consume the option of defeating the Dynamic Range Contol metadata, but some do not. Decodes with six discete channel outputs (full 5.1-channel capability) typically offe this option. Decodes with steeo, mono, o RF-emodulated outputs, such as those found on DVD playes and set-top boxes, often do not. In these cases, the decode automatically applies the most appopiate DRC metadata fo the decode s opeating mode. The Dolby Digital steam caies metadata fo the two possible opeating modes in the decode. The opeating modes ae known as Line mode and RF mode due to the type of output they ae typically associated with. Line mode is typically used on decodes with six- o two-channel line-level outputs and RF mode is used on decodes that have an RF-emodulated output. Full-featued decodes allow the consume to select whethe to use DRC and if so, which opeating mode to use. The consume sees options such as Off, Light Compession, and Heavy Compession instead of None, Line mode, and RF mode. Advanced decodes may also allow custom scaling of the DRC metadata. All that needs to be done duing metadata authoing, o encoding, is selection of the dynamic ange contol pofiles fo Line mode and RF mode. The pofiles ae descibed in the following sections. Note: While the use of DRC modes duing decoding is a consume-selectable featue, the Dialogue Level paamete setting is not. Theefoe, setting the Dialogue Level paamete popely is essential befoe peviewing a DRC pofile. Line Mode Line mode offes these featues: Low-level signal boost compession scaling is allowed. High-level signal cut compession scaling is allowed when not downmixing. The nomalized dialogue level is epoduced fom the decode at a constant loudness level of 31 dbfs Leq(A), assuming the Dialogue Level paamete is set coectly. Line-level o powe-amplified outputs fom two-channel set-top decodes, twochannel digital televisions, 5.1-channel digital televisions, Dolby Digital A/V suound decodes, and outboad Dolby Digital adaptes use Line mode. 7
Dolby Laboatoies, Inc. Consume contol of the dynamic ange is limited when downmixing. Poducts with steeo o mono outputs do not usually allow consume scaling of Line mode. This is because these devices ae usually downmixing (fo example, when eceiving a 5.1-channel signal). Howeve, in these poducts, the consume may have a choice between Line mode and RF mode. RF Mode In RF mode, high- and low-level compession scaling is not allowed. When RF mode is active, that compession pofile is always fully applied. RF mode is designed fo poducts (such as set-top boxes) that geneate a downmixed signal fo connection to the RF/antenna input of a television set; howeve, it is also useful in situations whee heavy DRC is equied fo example, when small PC speakes ae used fo DVD playback. In RF mode, the oveall pogam level is aised 11 db, this esults in dialogue being epoduced at a level of 20 dbfs Leq(A), while the peaks ae limited to pevent signal oveload in the D/A convete. By limiting headoom, sevee ovemodulation of television eceives is pevented. The 11 db gain povides an aveage loudness level that compaes well with existing analog television boadcasts. In some situations it may be necessay to futhe constain signal peaks above the aveage dialogue level so that thee is less than 20 db headoom. The selection of a suitable RF mode pofile achieves this. 8
Dolby Laboatoies, Inc. Dynamic Range Contol Pofiles Six peset DRC pofiles ae available to content poduces: Film Light, Film Standad, Music Light, Music Standad, Speech, and None. Each is applied in the patten shown in Figue 2. Low Output Level High Dialogue Level Setting Boost Range Null Band Centeed at the Dialogue Level Setting Ealy Cut Range Unity Gain Cut Range Low Input Level High Figue 2 DRC Pofile In each case, the cente of the null band is assigned to the egion suounding o adjacent to the Dialogue Level paamete setting, and the DRC pofile is applied in elation to that level. Hee ae the details of the ange fo each pofile. Film Light Max Boost: 6 db (below 53 db) Boost Range: 53 to 41 db (2:1 atio) Null Band Width: 20 db ( 41 to 21 db) Ealy Cut Range: 26 to 11 db (2:1 atio) Cut Range: 11 to +4 db (20:1 atio) Film Standad Max Boost: 6 db (below 43 db) Boost Range: 43 to 31 db (2:1 atio) Null Band Width: 5 db ( 31 to 26 db) Ealy Cut Range: 26 to 16 db (2:1 atio) Cut Range: 16 to +4 db (20:1 atio) Music Light (No ealy cut ange) Max Boost: 12 db (below 65 db) Boost Range: 65 to 41 db (2:1 atio) Null Band Width: 20 db ( 41 to 21 db) Cut Range: 21 to +9 db (2:1 atio) 9
Dolby Laboatoies, Inc. Music Standad Max Boost: 12 db (below 55 db) Boost Range: 55 to 31 db (2:1 atio) Null Band Width: 5 db ( 31 to 26 db) Ealy Cut Range: 26 to 16 db (2:1 atio) Cut Range: 16 to +4 db (20:1 atio) Speech Max Boost: 15 db (below 50 db) Boost Range: 50 to 31 db (5:1 atio) Null Band Width: 5 db ( 31 to 26 db) Ealy Cut Range: 26 to 16 db (2:1 atio) Cut Range: 16 to +4 db (20:1 atio) None No DRC pofile selected. The dialogue level paamete (dialnom) is still applied. These choices ae available to the content poduce fo both Line mode and RF mode. The content poduce chooses which of these pofiles to assign to each mode; when the consume o decode selects a DRC mode, the pofile chosen by the poduce is applied. In addition to the DRC pofile, metadata can limit signal peaks to pevent clipping duing downmixing. This metadata, known as oveload potection, is inseted by the encode only if necessay. Fo example, conside a 5.1-channel pogam with signals at digital full-scale on all channels being played though a steeo, downmixed linelevel output. Without some fom of attenuation o limiting, the output signal would obviously clip. Coect setting of the Dialogue Level and DRC pofiles nomally pevents clipping and unnecessay application of automatic oveload potection. Note: DRC pofile settings ae dependent on an accuate dialogue level setting. Impope setting of the dialogue level paamete may esult in excessive and audible application of oveload-potection limiting. 4 Downmixing Downmixing is a function of Dolby Digital that allows a multichannel pogam to be epoduced ove fewe speake channels than the numbe fo which the pogam is optimally intended. Simply put, downmixing allows consumes to enjoy a DVD o digital television boadcast without equiing a full-blown home theate setup. As with steeo mixing whee the mix is monitoed in mono on occasion to maintain compatibility, multichannel audio mixing equies the enginee to efeence the mix to fewe speake channels to ensue compatibility in downmixing situations. In this way, Dolby Digital, using the metadata paametes that contol downmixing, is an equal oppotunity technology, in that evey consume who eceives the Dolby Digital data steam can enjoy the best audio epoduction possible, egadless of the playback system. 10
Dolby Laboatoies, Inc. It is impotant to conside the output signals fom each piece of equipment that can eceive a Dolby Digital pogam in the home. Table 2 shows the output types fom diffeent equipment. Table 2 Outputs fom Dolby Digital Signal Pocessing Equipment Output Equipment Digital 5.1-Channel Analog Two-Channel Analog RF Remodulated 5.1-channel amplifie The standad home theate A/V amp 5.1-channel decode High-end DVD playe DVD playe PC Includes games consoles (some units) High-end set-top box Often HDTV Set-top box Usually SDTV IDTV TV set with an integated digital TV tune High-end TV Lage sceen TV with a 5.1-channel speake system Set-top boxes, used to eceive teestial, cable, o satellite digital television, typically offe an analog mono signal modulated on the RF/Antenna output, a line-level analog steeo signal, and an optical o coaxial digital output. DVD playes offe an analog steeo and a digital output, and some offe a six-channel analog output (fo a 5.1- channel pesentation). Potable DVD playes offe analog steeo, headphone, and digital outputs. DVD playes in computes and game consoles offe a digital output as well as analog steeo, headphone, and possibly six-channel analog outputs. 5.1- channel amplifies, decodes, and eceives have six-channel analog outputs and possibly six speake-level outputs. In all of these cases, a Dolby Digital decode ceates the analog audio output signal. In the case of the set-top box o DVD playe, the analog steeo output is a downmixed vesion of the Dolby Digital data steam. The digital output delives the Dolby Digital data steam to eithe a downsteam decode o an integated amplifie with Dolby Digital decoding. 11
Dolby Laboatoies, Inc. In each of these devices, the analog steeo output is one of two diffeent steeo downmixes. One type is a steeo-compatible Dolby Suound downmix, of the multichannel souce pogam that is suitable fo Dolby Suound Po Logic decoding. This kind of downmix is also called Po Logic o Left total/right total (Lt/Rt). The othe type is a simple steeo epesentation (called Left only/right only, o Lo/Ro) suitable fo playback on a steeo hi-fi o on headphones, and fom which a mono signal is deived fo use on an RF/Antenna output. The diffeence between the downmixes is how the Suound channels ae handled. The Lt/Rt downmix sums the Suound channels and adds them, in-phase to the Left channel and out-of-phase to the Right channel. This allows a Dolby Suound Po Logic decode to econstuct the L/C/R/S channels fo a Po Logic home theate. The Lo/Ro downmix adds the Left and Right Suound channels discetely to the Left and Right speake channels, espectively. This peseves the steeo sepaation fo steeo-only monitoing and poduces a mono-compatible signal. In all downmixes, the LFE channel is not included. On most home equipment, the consume can use the poduct s use inteface to choose the appopiate steeo output fo his playback system. The mono signal feeding the RF/Antenna output is usually deived fom the Lo/Ro downmix. Thee ae sepaate metadata paametes that goven the Lo/Ro and Lt/Rt downmixes. Cetain metadata paametes allow the enginee to select how the steeo downmix is constucted and which steeo analog signal is pefeed, but Lt/Rt is the default selection in all consume decodes. See Section 5, Paamete Definitions, fo moe infomation on individual paametes. Duing downmixing, as we have seen, the adjustment of Dynamic Range Contol paametes is limited. Boadly speaking, the steeo outputs use the Line mode compession pofile while the mono signal uses RF mode compession. As with dynamic ange contol, downmixing is ultimately dependent upon each consume s unique listening envionment. While the enginee must optimize the multichannel mix fo epoduction in an ideal listening envionment, it is also impotant to peview the mix in downmixing conditions to ensue compatibility with diffeent playback systems when selecting the downmixing metadata paametes. These peviews can be achieved in eal time using the DP570 Multichannel Audio Tool. 12
Dolby Laboatoies, Inc. 5 Paamete Definitions This section explains both pofessional and consume metadata paametes in geate detail. Metadata paametes include: Univesal paametes Extended Bitsteam Infomation (Extended BSI) paametes Extended BSI paametes ae active only when both the poduce chooses to use them and the consume s decode is capable of eading them. All decodes can successfully decode a metadata steam without Extended BSI paametes, and Extended BSI paametes tanslate seamlessly to decodes that ead only univesal paametes. Note: Univesal paametes include both pofessional and consume metadata. Table 1 in Section 1 shows the pofessional/consume distinction. Extended BSI paametes include only consume paametes. 5.1 Univesal Paametes All univesal paametes ae suppoted by Dolby E encodes and decodes; all except Pogam Configuation and Pogam Desciption Text ae suppoted by all Dolby Digital encodes and decodes. Pogam Configuation This paamete detemines how the audio channels ae gouped within a Dolby E bitsteam. Up to eight channels can be gouped togethe in individual pogams, whee each pogam contains its own metadata. The default setting is 5.1 + 2. Table 3 shows all the available configuations. 13
Dolby Laboatoies, Inc. Table 3 Pogam Configuation Settings Pogam Configuations 5.1 + 2 4 + 2 5.1 + 2 1 4 + 2 1 4 + 4 3 2 4 + 2 2 2 2 + 2 1 4 + 2 + 2 1 2 + 4 1 4 + 4 1 6 1 4 2 4 3 2 + 2 1 2 + 2 2 2 + 4 1 2 + 2 1 2 + 6 1 4 1 8 1 7.1 5.1 7.1 Scn Pogam Desciption Text This paamete is a 32-chaacte ASCII text field that allows the metadata autho to ente a desciption of the audio pogam. Fo example, this field may contain the name of the pogam (Movie Channel Pomo), a desciption of the pogam souce (Football Main Feed), o the pogam language (Danish). Dialogue Level The Dialogue Level paamete is discussed in Section 2, Dialogue Level. Channel Mode This paamete (also known as Audio Coding mode) indicates the active channels within the encoded bitsteam and affects both the encode and consume decode. This paamete instucts the encode which inputs to use fo this paticula pogam; it tells the decode what channels ae pesent in this pogam so the decode can delive the audio to the coect speakes. The setting is descibed as X/Y, whee X is the numbe of font channels (Left, Cente, Right) and Y the numbe of ea (Suound) channels. The availability of cetain channel modes depends on the Dolby Digital encode data ate and whethe the LFE channel is pesent. Fo example, you can t have a mono steam with an LFE channel (1.1!) o a 3/2 steam at 96 kbps. Appopiate data ates ae shown in the definition of each setting. Note: The pesence of the LFE channel is indicated though a diffeent metadata paamete (see LFE Channel). 14
Dolby Laboatoies, Inc. Channel Mode Setting Definition and Data Rate 1+1 Dual mono (not valid fo DTV boadcast o DVD poduction) 1/0 Mono Fom 56 kbps, usually 96 kbps 2/0 Steeo Fom 96 kbps, usually 192 kbps 3/0 Fom 256 kbps 2/1 Fom 256 kbps 3/1 Fom 320 kbps 2/2 Fom 320 kbps 3/2 Fom 384 kbps, often 448 kbps LFE Channel The status of the LFE Channel paamete indicates to a Dolby Digital encode whethe an LFE Channel is pesent within the bitsteam. Channel mode detemines whethe the LFE Channel paamete can be set. You must have at least thee channels to be able to add an LFE channel. LFE Channel Setting Enabled Disabled Bitsteam Mode This paamete descibes the audio sevice contained within the Dolby Digital bitsteam. A complete audio pogam may consist of a main audio sevice (a complete mix of all the pogam audio), an associated audio sevice compising a complete mix, o one main sevice combined with an associated sevice. To fom a complete audio pogam, it may be (but aely is) necessay to decode both a main sevice and an associated sevice using a maximum total bit ate of 512 kbps. Refe to the Guide to the Use of the ATSC Digital Television Standad, Document A/54 (see www.atsc.og) fo futhe infomation. Although a detailed desciption of each option follows, in pactice, most pogamming uses the default setting, Complete Main. An example of an exception to this ule is a special kaaoke DVD, o an emegency sevice within digital television. 15
Dolby Laboatoies, Inc. Bitsteam Mode Setting Complete Main (CM) Main M&E (ME) Assc. Visual Imp. (VI) Assc. Hea Imp. (HI) Assc. Dialogue (D) Assc. Commentay (C) Assc. Emegency (E) Assc. Voice Ove (VO) Main Sv Kaaoke (K) Definition CM flags the bitsteam as the main audio sevice fo the pogam and indicates that all elements ae pesent to fom a complete audio pogam. Cuently, this is the most common setting. The CM sevice may contain fom one (mono) to six (5.1) channels. The bitsteam is the main audio sevice fo the pogam, minus a dialogue channel. The dialogue channel, if any, is intended to be caied by an associated dialogue sevice. Diffeent dialogue sevices can be associated with a single ME sevice to suppot multiple languages. This is typically a single-channel pogam intended to povide a naative desciption of the pictue content to be decoded along with the main audio sevice. The VI sevice may also be a complete mix of all pogam channels, compising up to six channels. This is typically a single-channel pogam intended to convey audio that has been pocessed fo inceased intelligibility and decoded along with the main audio sevice. The HI sevice may also be a complete mix of all pogam channels, compising up to six channels. This is typically a single-channel pogam intended to povide a dialogue channel fo an ME sevice. If the ME sevice contains moe than two channels, the D sevice is limited to only one channel; if the ME sevice is two channels, the D sevice can be a steeo pai. The appopiate channels of each sevice ae mixed togethe (equies special decodes). This is typically a single-channel pogam intended to convey additional commentay that can be optionally decoded along with the main audio sevice. This sevice diffes fom a dialogue sevice because it contains an optional, athe than a equied, dialogue channel. The C sevice may also be a complete mix of all pogam channels, compising up to six channels. This is a single-channel sevice that is given pioity in epoduction. When the E sevice appeas in the bitsteam, it is given pioity in the decode and the main sevice is muted. This is a single-channel sevice intended to be decoded and mixed to the Cente channel (equies special decodes). The bitsteam is a special sevice fo kaaoke playback. In this case, the Left and Right channels contain music, the Cente channel has a guide melody, and the Left and Right Suound channels cay optional backing vocals. Line Mode Compession Pofile Line mode is discussed in Section 3, Dynamic Range Contol. RF Mode Compession Pofile RF mode is discussed in Section 3, Dynamic Range Contol. 16
Dolby Laboatoies, Inc. RF Ovemodulation Potection This paamete is designed to potect against ovemodulation when a decoded Dolby Digital bitsteam is RF modulated. When enabled, the Dolby Digital encode includes pe-emphasis in its calculations fo RF Mode compession. The paamete has no effect when decoding using Line mode compession. Except in ae cases, this paamete should be disabled. RF Ovemodulation Potection Setting Enabled Disabled Cente Downmix Level When the encoded audio has thee font channels (L, C, R), but the consume has only two font speakes (left and ight), this paamete indicates the nominal downmix level fo the Cente channel with espect to the Left and Right channels. Dolby Digital decodes use this paamete duing downmixing in Lo/Ro mode when Extended BSI paametes ae not active. Cente Downmix Level Setting Definition 0.707 ( 3 db) default The Cente channel is attenuated 3 db and sent to the Left and Right channels. 0.596 ( 4.5 db) The Cente channel is attenuated 4.5 db and sent to the Left and Right channels. 0.500 ( 6 db) The Cente channel is attenuated 6 db and sent to the Left and Right channels. Suound Downmix Level When the encoded audio has one o moe Suound channels, but the consume does not have suound speakes, this paamete indicates the nominal downmix level fo the Suound channel(s) with espect to the Left and Right font channels. Dolby Digital decodes use this paamete duing downmixing in Lo/Ro mode when Extended BSI paametes ae not active. Suound Downmix Level Setting Definition 0.707 ( 3 db) default The Left and Right Suound channels ae each attenuated 3 db and sent to the Left and Right font channels, espectively. 0.5 ( 6 db) Same as above, but the signal is attenuated 6 db. 0 ( 999 db) The Suound channel(s) ae discaded. 17
Dolby Laboatoies, Inc. Dolby Suound Mode This paamete indicates to a Dolby Digital decoding poduct that also contains a Dolby Po Logic decode (fo example a 5.1-channel amplifie), whethe o not the two-channel encoded bitsteam contains a Dolby Suound (Lt/Rt) pogam that equies Po Logic decoding. Decodes can use this flag to automatically switch on Po Logic decoding as equied. Dolby Suound Mode Setting Not Dolby Suound Dolby Suound Not Indicated Definition The bitsteam contains infomation that was not encoded in Dolby Suound. The bitsteam contains infomation that was encoded in Dolby Suound. Afte Dolby Digital decoding, the bitsteam is decoded using Po Logic. Thee is no indication eithe way. Audio Poduction Infomation This paamete indicates whethe the mixing level and oom type values ae valid. If Yes, then a eceive o amplifie could use these values as descibed below. If No, then the values in these fields ae invalid. In pactice, only high-end consume equipment implements these featues. Audio Poduction Infomation Setting Yes No Definition Mixing Level and Room Type paametes ae valid. Mixing Level and Room Type paametes ae invalid and should be ignoed. Mixing Level The Mixing Level paamete descibes the peak sound pessue level (SPL) used duing the final mixing session at the studio o on the dubbing stage. The paamete allows an amplifie to set its volume contol such that the SPL in the eplay envionment matches that of the mixing oom. This contol opeates in addition to the dialogue level contol, and is best thought of as the final volume setting on the consume s equipment. This value can be detemined by measuing the SPL of pink noise at studio efeence level and then adding the amount of digital headoom above that level. Fo example, if 85 db equates to a efeence level of 20 dbfs; the mixing level is 85 + 20, o 105 db. Mixing Level Setting 80 to 111 db in 1 db incements 18
Dolby Laboatoies, Inc. Room Type The Room Type paamete descibes the equalization used duing the final mixing session at the studio o on the dubbing stage. A Lage oom is a dubbing stage with the industy standad X-cuve equalization; a Small oom has flat equalization. This paamete allows an amplifie to be set to the same equalization as that head in the final mixing envionment. Room Type Setting Not Indicated Lage Small Copyight Bit This paamete indicates whethe the encoded Dolby Digital bitsteam is copyight potected. It has no effect on Dolby Digital decodes and its pupose is puely to povide infomation. Copyight Bit Setting Yes No Oiginal Bitsteam This paamete indicates whethe the encoded Dolby Digital bitsteam is the maste vesion o a copy. It has no effect on Dolby Digital decodes and its pupose is puely to povide infomation. Oiginal Bitsteam Setting Yes No 19
Dolby Laboatoies, Inc. Note: The paametes DC Filte, Lowpass Filte, LFE Lowpass Filte, Suound 3 db Attenuation, and Suound Phase Shift appea afte the Extended BSI paametes on Dolby E and Dolby Digital equipment menus. DC Filte This paamete detemines whethe a DC-blocking 3 Hz highpass filte is applied to the main input channels of a Dolby Digital encode pio to encoding. This paamete is not caied to the consume decode. It is used to emove DC offsets in the pogam audio and would only be switched off in exceptional cicumstances. DC Filte Setting Enabled Disabled Lowpass Filte This paamete detemines whethe a lowpass filte is applied to the main input channels of a Dolby Digital encode pio to encoding. This filte emoves highfequency signals that ae not encoded. At the suitable data ates, this filte opeates above 20 khz. In all cases it pevents aliasing on decoding and is nomally switched on. This paamete is not passed to the consume decode. Lowpass Filte Setting Enabled Disabled LFE Lowpass Filte This paamete detemines whethe a 120 Hz eighth-ode lowpass filte is applied to the LFE channel input of a Dolby Digital encode pio to encoding. It is ignoed if the LFE channel is disabled. This paamete is not sent to the consume decode. The filte emoves fequencies above 120 Hz that would cause aliasing when decoded. This filte should only be switched off if the audio to be encoded is known to have no signal above 120 Hz. LFE Lowpass Filte Setting Enabled Disabled Suound 3 db Attenuation The Suound 3 db Attenuation paamete detemines whethe the Suound channel(s) ae attenuated 3 db befoe encoding. The attenuation actually takes place inside the Dolby Digital encode. It balances the signal levels between theatical 20
Dolby Laboatoies, Inc. mixing ooms (dubbing stages) and consume mixing ooms (DVD o TV studios). Consume mixing ooms ae calibated so that all five main channels ae at the same sound pessue level (SPL). To maintain compatibility with olde film fomats, theatical mixing ooms calibate the SPL of the Suound channels 3 db lowe than the font channels. The consequence is that signal levels on tape ae 3 db loude. Theefoe, to convet fom a theatical calibation to a consume mix, it is necessay to educe the Suound levels by 3 db by enabling this paamete. Suound 3 db Attenuation Setting Enabled Disabled Suound Phase Shift This paamete causes the Dolby Digital encode to apply a 90-degee phase shift to the Suound channels. This allows a Dolby Digital decode to ceate an Lt/Rt downmix simply. Fo most mateial, the phase shift has a minimal impact when the Dolby Digital pogam is decoded to 5.1 channels, but it povides an Lt/Rt output that can be decoded with Po Logic to L, C, R, S, if desied. Howeve, fo some phasecitical mateial (such as music) this phase shift is audible when listening in a 5.1- channel fomat. Likewise, some mateial downmixes to a satisfactoy Lt/Rt signal without needing this phase shift. It is theefoe impotant to balance the needs of the 5.1 mix and the Lt/Rt downmix fo each pogam. The default setting is Enabled. Suound Phase Shift Setting Enabled Disabled 5.2 Extended Bitsteam Infomation Paametes In esponse to equests fom content poduces, Dolby Laboatoies modified the definitions of seveal metadata paametes fom thei oiginal definition as descibed in ATSC document A/52. The evised definitions allow moe infomation to be caied about the audio pogam and also allow moe choices fo steeo downmixing. When the metadata paametes caied in Dolby Digital wee fist descibed, they wee geneically called Bitsteam Infomation, o BSI. We efe to the additional paamete definitions as Extended BSI. Because the evised definitions affect metadata paametes that wee not used by the consume decodes, all decodes will be compatible with the evised bitsteam. Newe decodes that ae pogammed to detect and decode the new paametes will be able to implement the new featues Extended BSI povides. 21
Dolby Laboatoies, Inc. Poducts that allow emulation of the effects of metadata, such as the DP570, nomally have a featue that allows emulation of a new (o compliant) decode o a legacy decode. Pefeed Steeo Downmix Mode This paamete allows the poduce to select eithe the Lt/Rt o the Lo/Ro downmix in a consume decode that has steeo outputs. Consume eceives ae able to oveide this selection, but this paamete povides the oppotunity fo a 5.1-channel soundtack to play in Lo/Ro mode without use intevention. This is especially useful on music mateial. Pefeed Steeo Downmix Mode Setting Not Indicated Lt/Rt Pefeed Lo/Ro Pefeed Lt/Rt Cente Downmix Level This paamete indicates the level shift applied to the Cente channel when adding to the left and ight outputs as a esult of downmixing to an Lt/Rt output. Its opeation is simila to the cente downmix level in the univesal metadata. Lt/Rt Cente Downmix Level Setting 1.414 (+3.0 db) 1.189 (+1.5 db) 1.000 (0.0 db) 0.841 ( 1.5 db) 0.707 ( 3.0 db) 0.595 ( 4.5 db) 0.500 ( 6.0 db) 0.000 ( 999 db) 22
Dolby Laboatoies, Inc. Lt/Rt Suound Downmix Level This paamete indicates the level shift applied to the Suound channels when downmixing to an Lt/Rt output. Its opeation is simila to the suound downmix level in the univesal metadata. Lt/Rt Suound Downmix Level Setting 0.841 ( 1.5 db) 0.707 ( 3.0 db) 0.595 ( 4.5 db) 0.500 ( 6.0 db) 0.000 ( 999 db) Lo/Ro Cente Downmix Level This paamete indicates the level shift applied to the Cente channel when adding to the left and ight outputs as a esult of downmixing to an Lo/Ro output. When Extended BSI paametes ae active, this paamete eplaces the Cente Downmix Level paamete in the univesal paametes. Lo/Ro Cente Downmix Level Setting 1.414 (+3.0 db) 1.189 (+1.5 db) 1.000 (0.0 db) 0.841 ( 1.5 db) 0.707 ( 3.0 db) 0.595 ( 4.5 db) 0.500 ( 6.0 db) 0.000 ( 999 db) 23
Dolby Laboatoies, Inc. Lo/Ro Suound Downmix Level This paamete indicates the level shift applied to the Suound channels when downmixing to an Lo/Ro output. When Extended BSI paametes ae active, this paamete eplaces the Suound Downmix Level paamete in the univesal paametes. Lo/Ro Suound Downmix Level Setting 0.841 ( 1.5 db) 0.707 ( 3.0 db) 0.595 ( 4.5 db) 0.500 ( 6.0 db) 0.000 ( 999 db) Suound EX Mode This paamete is used to identify the encoded audio as mateial encoded in Suound EX TM. This paamete is only used if the encoded audio has two Suound channels. An amplifie o eceive with Dolby Digital Suound EX decoding can use this paamete as a flag to switch the decoding on o off automatically. The behavio is simila to that of the Dolby Suound Mode paamete. Suound EX Mode Not Indicated Not Suound EX Dolby Suound EX A/D Convete Type This paamete allows audio that has passed though a paticula A/D convesion stage to be maked as such, so that a decode may apply the complementay D/A pocess. A/D Convete Type Setting Standad HDCD 24
Dolby Laboatoies, Inc. 6 Metadata Combinations Table 4 povides examples of combinations of paametes that could be used as a peset. Note: These paamete settings ae povided as examples to demonstate that diffeent settings can be saved, named, and bought up as needed fo quick use in diffeent situations. The settings ae not ecommendations, but could be used as a stating point fom which to ceate you own metadata values. Table 4 Examples of Possible Metadata Settings (Extended Bitsteam Infomation paametes ae in italics.) Paamete Action Film (5.1) Dama (Lt/Rt) Local News (Mono) Music (5.0) Live Spoting Events (5.0) Pogam Configuation 5.1+2 o 5.1 5.1+2, 4 2, o 3 2 4 2, 3 2, 8 1, o 6 1 5.1+2 o 5.1 5.1+2 o 5.1 Pogam Desciption Film Dama News Music Spots Dialogue Level 27 db 27 db 20 db 15 db 18 db Channel Mode 3/2L 2/0 1/0 3/2 3/2 LFE Channel Enabled N/A N/A Disabled Disabled Bitsteam Mode Complete Complete Complete Complete Complete Main Main Main Main Main Line Mode Po Film Music Film Light Speech Standad Standad Film Standad RF Mode Po Film Music Film Light Speech Standad Standad Film Standad RF Ovmd Potect Disabled Disabled Disabled Disabled Disabled Cente Dwnmix 0.707 db 0.707 db 0.707 db N/A N/A Lev ( 3 db) ( 3 db) ( 3 db) Snd Dwnmix Lev 0.707 db 0.707 db 0.707 db N/A N/A ( 3 db) ( 3 db) ( 3 db) Dolby Snd Mode N/A Dolby Suound N/A N/A N/A Audio Pod Info Yes Yes No Yes No Mixing Level 101 db 90 db N/A 95 db N/A Room Type Lage Small N/A Lage N/A Copyight Yes Yes Yes Yes Yes Oiginal Bitsteam Yes Yes Yes Yes Yes Pefeed Steeo Lt/Rt Lt/Rt Lo/Ro Lt/Rt N/A Downmix Pefeed Pefeed Pefeed Pefeed Lt/Rt Cente Downmix Level 0.707 ( 3 db) 1.0 (0 db) N/A 0.707 ( 3 db) N/A 25
Dolby Laboatoies, Inc. (Extended Bitsteam Infomation paametes ae in italics.) Paamete Action Film (5.1) Dama (Lt/Rt) Local News (Mono) Music (5.0) Live Spoting Events (5.0) Lt/Rt Suound Downmix Level Lo/Ro Cente Downmix Level Lo/Ro Suound Downmix Level Dolby Suound EX Mode 0.707 ( 3 db) 0.595 ( 4.5 db) N/A 0.707 ( 3 db) N/A N/A N/A N/A N/A N/A N/A N/A Dolby Suound EX N/A 0.707 ( 3 db) 0.595 ( 4.5 db) N/A N/A N/A N/A A/D Convete Type Standad Standad Standad Standad Standad DC Filte Enabled Enabled Enabled Enabled Enabled Lowpass Filte Enabled Enabled Enabled Enabled Enabled LFE Lowpass Filte Enabled N/A N/A N/A N/A Snd 3 db Atten Enabled N/A N/A Disabled Disabled Snd Phase Shift Enabled N/A N/A Enabled Enabled 26