To Quickly create a Dolby Digital file from an AIFF or WAV Master:
• Launch A.Pack—unless you have modified the A.Pack preferences, the Instant Encoder will open (see Fig. 6-18a).
• In the Audio Tab, adjust the Settings for the file desired:
– Leave Target SystematDVD-Video.
– Set Audio Coding ModetoStereo 2/0.
– Set Data Rateto192 Kbpsfor Stereo.
– Set Dialog Normalizationto–31; hit ENTER.
– Leave Bitstream Modeat “Complete Main.”
• In the Bitstream Tab, leave the settings unchanged.
• In the Preprocessing tab, turn Compression Off.
• In the same tab, turn RF Overmodulation ProtectionOff.
• Load the file to be encoded into A.Pack’s file grid source tabs—drag files into tabs, or click a channel’s tab to open a Dialog box.
• Click Encode; Set the Destination Location and Final File Name.
NOTE!
Failure to Load an Input File will cause an error mes- sage (see Fig. 6-18b).
Figure 6-18b — “No Input File” warning dialog.
Preparing to use A.Pack
(Additional detailed information about using A.Pack can be found by consulting Appendix B of the DVD Studio Pro 2 or 3 Helpfile.)
IMPORTANT!
AIFF or WAV (PCM) files for DVD use must be at the 48 KHzsample rate. If you are importing sound from a CD library, be sure to Exportthe captured 44.1 KHz file to 48 KHz using the QuickTime Pro player.
Using the A.Pack Instant Encoder
To create a Dolby Digital encode using the Instant Encoder window, you will need to make settings choices in the three available tabs that organize sets of parameters. Note that the manner of changing set- tings is common to both the Instant Encoderand the Batch List.
In the Audio Tab:
• Set the Target System(always DVD Video).
• Set the Audio Coding Mode(channel configuration).
• Set the Data Rate(the Encode Bit Rate).
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Figure 6-18a — A.Pack Instant Encoder Window.
• Set the Dialog Normalization Setting.
• Set the Bit Stream Mode(a MetaData label).
In the Bitstream Tab:
• If this is a 5.1 encode, set the Center Downmix level.
• If this is a 5.1 encode, set the Surround Downmix level.
• If this is an Lt/Rt encode, set Dolby Surround mode.
• If a Copyright Exists,check the checkbox.
• If this is the Original Bitstream,check the checkbox.
• If needed, check the Audio Production Informationbox.
• Set the Peak Mixing Level, based on mixing room info.
• Set the Room Type, based on mixing room information.
In the Preprocessing Tab:
• Set/Verify the Compression setting.
• Set/Verify the General settings.
• Set/Verify the Full Bandwidth Channels settings.
• Set/Verify the LFE Channel setting.
• Set/Verify the Surround Channels settings.
The File Grid (Input Channels):
• Load the Source files into the appropriate Grid locations: Left into Left, Right into Right, etc. (See Fig. 6-19.)
Figure 6-19 — A.Pack Input Grid in Surround 5.1 Mode.
Loading the File Grid
Before encoding can take place, the File Grid Channels must be loaded with the source files required for the encode. To do so, click on a Channel in the Grid, and use the File Dialog box to locate the file for that channel, or… (easier) drag and drop a file onto the proper channel in the Grid. Select the appro- priate channel from within the file if a dialog is offered. (Mono files will not require choosing a channel from within the file. AIFF files are fre- quently stereo, and will offer this choice to be made).
TIP!
Use the Batch List(detailed later) when you have a lot of files to convert and wish to do so all at once or unattended. The Instant Encoderwill require manually loading each file and setting the job parameters by hand.
Settings Preferences in the Audio Tab (in Detail)
Setting the Target System
To properly use A.Pack, you have to identify the sys- tem for which the Audio bitstream is being created:
DVD-Video, DVD-Audio, or Generic AC-3. The proper selection is always DVD-Video(see Fig. 6-20 and 6-21).
Figure 6-21 — The Target System.
Setting the Audio Coding Mode
• Audio Coding Modedefines the channel configuration of the Dolby Digital bitstream you are encoding. It can vary from Mono to 5.1 with or without LFE. NOTE that Dolby denotes the channel configuration as a two digit series, i.e., 3/2, or 2/0, where the first digit indicates the number of Front Channels (1, 2, or 3) and the second digit indicates the number of surround channels (0, 1, or 2) (see Fig. 6-22).
Most DVD audio programs are usually Stereo (2/0) or 5.1 Surround (3/2 w/LFE).
• Select the desired Audio Coding Modepop- up to indicate the number of channels you are encoding—Standard Stereo is 2/0 (L, R).
Some programs you encode may be 5.1 or other channel configurations.
• If you are using the LFE channel, check the Enable Low Frequency Effectscheckbox.
Leave it off if you are not doing a format that requires it.
• Once you’ve selected the Audio Coding Mode, you MUST continue on to verify or set the Data Rate.
Setting the Data Rate (the All-Important Encode Rate)
Setting a Data Ratefor Encoding Audio is analo- gous to setting the MPEG Encode rate for Video (see Fig. 6-23). The accepted standard rates for AC-3 are 192 kBps for Stereo and 384 kBps for 5.1. Note that the allowable encode rates displayed in the pop-up will vary depending on the Audio Coding Mode (channel configuration) you have selected.
WARNING!
Under nocircumstances should a Dolby Digital data rate everexceed 448 Kbps for DVD. You’ll probably find Dolby Digital encode rates below 192 kbps unsat- isfactory for Stereo Sound files, but possibly workable for Mono sound files. Rates under 96 Kbps are not recom- mended for use at all.
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Figure 6-20 — The Audio Tab.
Figure 6-22 — The Audio Coding Mode pop-up.
Figure 6-23 — The Data Rate (encode rate) pop-up.
Setting the Dialog Normalization Setting
This is probably THE most misunderstood function in A.Pack! Dialog Normalization is a setting in the Dolby AC-3 spec that allows the Decoder to dynami- cally adjust the playback level, as needed (see Fig. 6- 24). The setting programmed at the time of encode tells the Decoder how much attenuation to add during playback. For typical Stereo files that have already been leveled, this function may be better left disabled.
Figure 6-24 — The Dialog Normalization parameter.
• To set the Dialog Normalizationvalue, click in the field and adjust the value. Valid values are from –1 to –31. To disablethe Dialog Normalization function, set it to –31.
• You MUSTbe sure to hit “ENTER” or
“RETURN” after entering the value, to close the field. If not, the value may not be set properly. To verify, check the file’s MetaData once your encode has been completed. (See the section on Monitoring your Dolby Digital encodes further on in this chapter).
Setting the Bit Stream Mode Parameter
Figure 6-25 — The Bit Stream Mode pop-up.
Dolby “MetaData” (labels or information) may be programmed into the AC-3 file, to define the purpose of this particular Audio bitstream. These labels include Complete Main, Music and Effects, Commentary, Dialog, and more. (See Fig. 6-25.)
• To set the Bit Stream mode, click on the Bit Stream Modepop-up, and select the desired label. In many cases, Complete Main is the appropriate setting—it is always the default value. In any case, this setting does NOT affect the way in which the Dolby Decoder reproduces the bitstream. It’s just a label.
(See Fig. 6-26.)
Settings in the Bitstream Tab (in Detail)
Figure 6-26 — The Bitstream Tab.
If this is a 5.1 encode, set the Center Downmix Level:
The Center channel of a Surround Sound bitstream can be mixed into the Analog Left/Right Stereo Outputs of your DVD player, attenuated per the downmix level programmed in at the time of encod- ing. Setting this parameter controls the level of the Center channel present in the final Stereo Downmix.
Figure 6-27 — Setting the Center Downmix parameter.
• To set the Center Downmixlevel, click on the Center Downmix pop-up and select the appropriate setting. (See Fig. 6-27.)
In many cases, the default setting of -3.0 dB may be perfectly appropriate. For further information, you may wish to consult the Dolby Metadata GuidePDF, available from the Dolby website. We’ve included it in the Dolby folder on the accompanying DVD.
If this is a 5.1 encode, set the Surround Downmix Level:
This parameter controls the level of the Left and Right Surround channels in the final Stereo Downmix.
Figure 6-28 — Setting the Surround Downmix.
Surround Sound bitstreams can output their mono or stereo surround information from the Analog Front Left/Right Outputs of your DVD player, if this infor- mation is encoded into the bitstream.
• To set the Surround Downmixlevel, click on the Surround Downmix pop-up and select the appropriate setting. (See Fig. 6-28.) In many cases, the default setting of -3.0 dB may be perfectly appropriate. At this setting, the left and right surround channels are each attenuated 3 dB and sent to the left and right front channels, respectively.
At –6 dB, the output routing is the same as –3dB, but the signal is attenuated 6 dB. At the –°°dB (Infinity) setting, the surround channel(s) are discarded.
If this is an Lt/Rt encode, set Dolby Surround mode:
Dolby Surround Mode is a special two-channel con- figuration, which actually contains FOUR channels of discrete audio information: Left, Center, Right, and a Mono Surround channel, electronically matrixed into two channels. These files are known by
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the special code Lt/Rt(Left Total/Right Total). If the file is Lt/Rt, setting this property can cause a Dolby Surround Pro Logic decoder to engage in order to properly decode four-channel Dolby Surround infor- mation encoded in the file’s two channels.
Figure 6-29 — Dolby Surround Mode.
Dolby Surround Mode would only be required if the original sound mix was a four-channel mix contain- ing L, C, R, and mono Surround) that has been processed by a Dolby Matrix encoder. If this is true, then set the Dolby Surround Mode property to Dolby Surround Encoded. (See Fig. 6-29.)
If the original sound mix was NOT a four-channel mix with mono surround, then Dolby Surround Mode is NOT required, and this property should be set to NOT Indicated, or NOT Dolby Surround Encoded. If you are NOT sure about this setting, leave it Not Indicated. Odds are you will be correct. It may also be possible to use this setting to decode files prepared in the Ultra-Stereo format, since that is a similar matrixed L, C, R, S format as Dolby Surround.
If a Copyright Exists, check the designated checkbox:
Figure 6-30 — The Copyright and Content checkboxes.
Dolby MetaData can contain a flag bit to indicate if the audio content of the bitstream is currently under Copyright. (See Fig. 6-30.)
• The Default setting is “on.” To turn this flag
“off,” click on the Copyright Exists checkbox to uncheck it. Click again to check it if needed.
If this is an Original Bitstream, check the checkbox:
Dolby Metadata can contain a flag bit to indicate if the audio content of the bitstream is the Original Dolby Bitstream, or a copy. (See Fig. 6-30.)
• The Default setting is “on,” meaning this is the original bitstream created of this content. To denote this is not the original bitstream, click on the Content is Original checkbox, to uncheck it. Click again to check it if needed.
If appropriate, check the Audio Production Information box:
Figure 6-31 — Setting Audio Prod’n Info.
The default of this parameter is OFF, but by turning it ON, it is possible to advise Dolby Digital decoders that the accompanying reference information is valid, and it may be used to adjust playback levels. (See Fig. 6-31.)
Set the Peak Mixing Level, based on mixing info:
This parameter defines the Peak mixing level used during the surround mix, but is only referenced by the decoder if the Audio Production Information is checked on.
Set the Room Type, based on mixing room information:
This parameter defines the Type of mixing room or stage used during the surround mix, but is only ref- erenced by the decoder if the Audio Production Information is checked on. The Large room X-curve parameter would be checked if the audio file was cre- ated in a traditional theatrical mixing (dubbing) stage, whose audio characteristics follow the Academy Curve—a specific equalization curve that attenuates high frequencies to emulate the playback characteristics of a movie theater.
Settings in the Preprocessing Tab
Setting the Compression Factor
A.Pack can apply different types of Program Compression to assist in leveling out the dynamic range (not always a good thing), depending on the kind of program you are encoding—Film, Music, or Speech. You may find, however, that turning Compression off may be the right solution for mate- rial that is already dynamically leveled or doesn’t have large dynamic range swings.
• To apply a Program Compressiontype, or to deselect Compression, click on the
Compressionpop-up (as shown in Fig. 6-32) and drag to select your choice.
Setting the RF Overmodulation Protection
• According to Dolby Labs, this parameter is designed to protect against overmodulation
when a decoded Dolby Digital bitstream is RF modulated. When enabled, the Dolby Digital encoder includes pre-emphasis in its calculations for RF Mode compression. The parameter has no effect when decoding using Line Mode compression.
NOTE! Except in rare cases, this parameter should be disabled.
A.Pack can set or disable the RF Overmodulation Protection bit through a simple checkbox. Check if carefully, as it usually defaults to “On.”
• The Default is “on” (enabled). (See Fig.
6-33.) To disable the RF Overmodulation Protection bit, deselect the check box for this parameter.
NOTE that in recent versions of A.Pack, this may default to OFF.
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Figure 6-32 — Setting the Compression parameter.
Figure 6-33 — Setting the RF Overmodulation parameter.
Setting the Digital Deemphasis Parameter
Believe it or not, there is NO official Dolby explana- tion for this parameter in the Dolby Metadata Guide.
(See Fig. 6-34.)
• Since the parameter defaults to off, it’s best to leave it that way.
Setting the Low-Pass Filter (for Full Bandwidth Channels)
According to Dolby Labs, this parameter determines whether a lowpass filter is applied to the main input channels of a Dolby Digital encoder prior to encod- ing (see Fig. 6-35). This filter removes high-fre- quency signals that are not encoded. At the suitable data rates, this filter operates above 20 kHz. In all cases, it prevents aliasing on decoding and is nor- mally switched on. This parameter is not passed to the consumer decoder.
• To deselect Apply Low-Pass Filter(which defaults to “on”), click on the checkbox to deselect it (see Fig. 6-35).
Figure 6-34 — Setting the Digital Deemphasis parameter.
Figure 6-35 — Setting the Low-Pass Filter parameter.
Setting the DC Filter (for Full BW Channels)
According to Dolby Labs, this parameter determines whether a DC blocking 3 Hz highpass filter is applied to the main input channels of a Dolby Digital encoder prior to encoding. It is used to remove DC offsets in the program audio and would only be switched off in exceptional circumstances. This parameter is not carried to the consumer decoder.
• To deselect Apply DC Filter(which defaults toon), click on the checkbox to deselect it (see Fig. 6-36).
Figure 6-36 — Setting the Full BW Channels DC Filter parameter.
Setting the Low-Pass Filter (for LFE Channel)
According to Dolby Labs, this parameter determines whether a 120 Hz 8th order lowpass filter is applied to the LFE channel input of a Dolby Digital encoder prior to encoding. It is ignored if the LFE channel is disabled. This parameter is not sent to the consumer
decoder. The filter removes frequencies above 120 Hz that would cause aliasing when decoded. This fil- ter should only be switched off if the audio to be encoded is known to have no signal above 120 Hz.
• To deselect Apply Low-Pass Filter (which defaults to “on”), click on the checkbox to deselect it (see Fig. 6-37).
Figure 6-37 — Setting the LFE Low-Pass Filter parameter.
Setting the Surround Phase Shift
According to Dolby Labs, “This parameter causes the Dolby Digital encoder to apply a 90-degree phase shift to the surround channels.” This allows a Dolby Digital decoder to create an Lt/Rt downmix simply.
For most material, the phase shift has a minimal impact when the Dolby Digital program is decoded to 5.1 channels, but provides an Lt/Rt output that can be Pro Logic decoded to L, C, R, S, if desired.
However, for some phase-critical material (such as music), this phase shift is audible when listening in 5.1 channels. Likewise, some material downmixes to 157
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a satisfactory Lt/Rt signal without needing this phase shift. It is therefore important to balance the needs of the 5.1 mix and the Lt/Rt downmix for each program.
The default setting is Enabled.
• To disable the Apply 90-degree Phase-Shift to Surround Channelsparameter, click on the Apply 90-degree Phase-Shift checkbox (as shown in Fig. 6-38) to uncheck the selection.
Figure 6-38 — Setting the Surround Phase-Shift parameter.
Setting the 3 dB Attenuation in Surround Channels
According to Dolby Labs, the Surround 3 dB Attenuationparameter determines whether the sur- round channel(s) are attenuated 3 dB before encod- ing. The attenuation actually takes place inside the Dolby Digital encoder (in this case, A.Pack). It bal- ances the signal levels between theatrical mixing rooms (dubbing stages) and consumer mixing rooms (DVD or TV studios). Consumer mixing rooms are calibrated so that all five main channels are at the same sound pressure level (SPL). For compatibility
reasons with older film formats, theatrical mixing rooms calibrate the surround channels 3 dB lower in SPL than the front channels. The consequence is that signal levels on tape are 3 dB louder. Therefore, to convert to a consumer mix from a theatrical calibra- tion, it is necessary to reduce the surround levels by 3 dB by enabling this parameter.
• To apply the Surround Attenuation, click on theApply 3dB Attenuationcheckbox, shown in Figure 6-39.
Figure 6-39 — Setting the 3dB Surround Attenuation parameter.
Using the A.Pack Batch List
Use the Batch List(see Fig. 6-40) to encode multiple AIFF or WAV files into AC3 in an unattended man- ner. If you have used Compressor, Cleaner, or Media Cleaner Pro, you are probably familiar with the batch process concept. It saves you time, by freeing you up to continue your creative work while the computer does the AC-3 encoding automatically, unattended.
To use the A.Pack Batch List process:
• Select File > New Batch List…from the menu (Fig. 6-41) or open an existing Batch List with the Open…command.
Figure 6-41 — The Batch List command.
• A new Batch List will open with a default
“Job” created; (see Fig. 6-42). Each individual Encode will use a separate “Job”
in the batch list. Each entry in the Batch List has space for the details to be programmed.
• Modify the Audio Coding Modein the same way you configured the Instant Encoder. In theAudio Tabof the Batch List, select the desired configuration from the Audio Coding Mode pop-up.
• Load the Source File(s)into the appropriate channel tabs. This can be done by clicking on a “Select” button and then navigating to a file, or by dragging and dropping a file onto a channel box.
• Select the destination and filename of the completed encode using the “Set Output”
button. The Checkbox will enable or disable this file in the Batch.
• Adjust the encode Job settings in the Settings Tabs, in the same manner as you would adjust the settings in the Instant Encoder.
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Figure 6-40 — A.Pack Batch List.