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SurCode MLP - Owners ManualTable of Contents

1 Introduction to SurCode MLP 1Why Encode? 2How It Works 2ReBit 4Compression Amounts 4DVD-A Playing Time 4Two-channel Downmix 4Error Detection 4Channel Assignment 5File Types 5MLP Logs 5

2 Getting Started 7Open SurCode MLP 7

Name The File 7Select A Destination 8Select Files To Encode 9Press The Encode Button 9Listen To The MLP File 9Other Options 9

3 Main Screen 10Menu Bar 10Setup 11Options 11Help 11Destination 12Channel Assignment 12Soundfiles 12Clear 13Group Number 13Channel Bit/Sample Rate 13

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Mute/Solo 14Channel Name 14Encode Section 14Playback Section 15

4 Options 16Device Options 16Encoder Options 16Downmix Section 18ReBit Section 18Verification/Playback Section 18

5 Soundfiles 19Entering Soundfiles 19Clearing Soundfiles 20Channel Bit- and Sample-Rates 20Channel Assignment 20Channel Group Indicator 21

6 Downmix 22What Is Downmixing? 22Downmix Defaults 22Left/Right Downmix 23Channel Coefficients 24Channel Phase 24

Channel Mute 24Restore Defaults 25Downmix Clipping 25Downmix Parameters 25

7 Channel Assignment 26Why Use Groups? 26

Channel Assignments 27Assignment Options 27

8 Encode Section 28Encode Start and End Time 29

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The Encode Button 29The Stop Button 29

10 Playback Section 30

Source/Destination Select 30Transport Controls 31Current Location 31

11 Verification/Playback Section 32Verify Select 32Write Decoded File Select 33

Playback Select 33MLP Logs 33

12 ReBit (Bit-Depth Reduction) 34Why Is Bit-Depth Reduction Needed? 34Why Is SurCode MLPs ReBit Needed? 35How ReBit Works 36

The ReBit Section 37Manual Bit-Depth Reduction 37Automatic Bit-Depth Reduction 38ReBit Step Order 38Time Savings 39Worst-Case Scenario 40

13 Appendix A - Tables 41Compression Amounts 41DVD-A Playing Time 41Channel Assignments 42

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TECHNICAL SUPPORT:Please Read This Manual First!

[email protected]

Minnetonka Audio Software, Inc.

17113 Minnetonka Blvd. Suite 300Minnetonka, MN 55345

PH 952-449-6481Hours: 10:00AM - 6:00PM CST Mon.-Fri.

FAX 952-449-0318www.minnetonkaaudio.com

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Introduction to SurCode MLP

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1 Introduction to SurCode MLPWelcome to SurCode MLP the best way to encode high-resolution audio files for the DVD-Audio format. SurCode

MLP utilizes licensed encoding algorithms from MeridianInc. MLP stands for Meridian Lossless Packing, which isan encoding system designed to compress high-resolutionaudio files with bit-for-bit accuracy. Unlike the perceptual,or lossy audio data reduction systems used in DVD-Videoauthoring, MLP guarantees not to alter the final decoded

signal in any way. Instead, it simply packs the audio datamore efficiently into a smaller data rate.SurCode MLP is an intuitive Windows-based program thatsimplifies the steps involved in encoding a set of one or more audio files, while automatically verifying the accuracyof the resulting MLP file.

While this manual covers the wide number of choices andoptions built into SurCode MLP, please note that simplyentering soundfiles into their respective channels and hittingthe Encode button is all that is neccessary for most

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productions, as the default settings in SurCode MLP are based on industry standards and norms (see the GettingStarted chapter).

1.1 Why Encode?

MLP encoding has two primary benefits:

1. It minimizes the size of the compressed file, allowinga larger amount of audio to be stored on the DVD-Adisc.

2. It can reduce the maximum instantaneous peak datarate.

This second benefit is very important for DVD-Audio,which has an upper limit of 9.6Mbps (megabits per second).For example, six channels of 24-bit, 96kHz Linear PCM(Pulse Code Modulation) audio has a data rate of 13.82Mbps, which is much greater than the data throughputof the DVD-Audio system. This high data rate would alsolimit the playing time to approximately 45 minutes. MLPencoding can reduce the worst-case data rate to 9.6 Mbps,extending the playing time to the industry standard of 74minutes, as well as allowing bit-accurate high-resolutionsix-channel audio.

1.2 How It Works

Because MLP was originally designed with consumer applications in mind, one of its design aims was that any

complexity must be in the encoder instead of the decoder.The design of the decoder ensures that it will remainlossless regardless of hardware platform or processor implementation. In addition, the decoder is driven by

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information in the bitstream, allowing improved versions of the encoder to be developed without becomingincompatible with the installed base of decoders. MLP

encoding uses a combination of three methods to reduce thedata rate:

1. Lossless matrixing is used to reduce the correlation between channels.

2. Lossless waveform prediction is used to reduce theinter-sample correlation.

3. Entropy coding is used to reduce the data rate by effi-ciently encoding the most likely occurring values in theaudio data.

SurCode MLP does not make any assumptions about theassignment of channels, or the correlation betweenchannels, but takes advantage of whatever redundancy is inthe overall signal to encode the data using the smallest

possible bandwidth.In addition to these procedures for reducing the data rate,MLP uses stream buffering to reduce the variations in the

transmitted data rates, and absorb transients that are hard tocompress, in order to assure a maximum instantaneous peak data rate. The buffer allows the peak data rate to beminimized for virtually all practical audio data.If the audio data cannot be compressed within the specified

peak data rate, SurCode MLP will signal an error. The pro-

ducer can then use one or more options for reducing the datarate, or reducing the total space used by the recording, suchas Minnetonkas ReBit, described next.

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1.3 ReBitMinnetonka Audio Software has implimented a uniquetime-saving feature in SurCode MLP called ReBit thatenables users, in exteme cases, to avoid the necessity of re-mastering their material in order to pass through the MLPencoding process (see the ReBit chapter).

1.4 Compression AmountsSee Table 1 in Appendix A - Tables.

1.5 DVD-A Playing TimeSee Table 2 in Appendix A- Tables.

1.6 Two-channel Downmix

Content providers will often want to make a two-channel

version of a multi-channel audio stream available on aDVD-A disc, for consumers who only have two-channel playback capability.SurCode MLP provides an elegant and simple solution to

providing a two-channel downmix. The encoder includeslossless matrixing, which can encode a two-channel

downmix as a linear combination of the multi-channel mixand encode this alongside the multi-channel version on theDVD-A disc (see the Downmix chapter).

1.7 Error Detection

MLP also has powerful built-in error detection that allowsrapid recovery from bit-stream errors, and prevents anyerroneous noises, clicks, or pops following data errors.

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1.8 Channel Assignment

DVD-Audio supports up to six channels in one of 21combinations of channel assignments (see Table 3 in

Appendix A- Tables).The Channel Assignment combinations place thechannels into two groups, referred to as Group 1 and Group2. The significance of the group is that the sample-rates can

be specified independently for each group. However, thesample-rates within each group must be the same, and theGroup 2 sample-rate must be an even multiple of Group 1(see the Channel Assignment chapter).The DVD-Audio channel assignments 8 to 12 are almostidentical to the channel assignments 13 to 17, and differ only in the way the channels are grouped.

1.9 File Types

SurCode MLP processes data from one or more input files,with WAV and AIFF audio file formats directly supported. Note:

SurCode MLP does NOT support the Multi-Channel WAVfile format (Multiple mono WAV files must be used as inputto the encoder).

1.10 MLP Logs

A feature of SurCode MLP is the Encode Log (see Figure 1-1) generated by each encode pass. It gives you specificinformation about file types and rates, durations, andwhether the encode passed (including verification). WhenReBit (Bit-Depth Reduction) is active, the Log includes the

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steps taken in ReBit (see the ReBit chapter). The log can be saved for further reference.

Note: There is also a Verifier Log generated by SurCodeMLP after the Verify stage (see the Verification/Playback Section chapter).

Figure 1-1

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2 Getting Started

2.1 Open SurCode MLP

When you open SurCode MLP, you will see the MainScreen, shown in Figure 2-1 (see the Main Screen chapter also)..

Figure 2-1

2.2 Name The File

You will need to name the MLP file (the file that willcontain the encoded MLP stream). The MLP file type is notselectable and has a default in the Save as type: window

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to MLP Encoded Files (*.mlp). This is because SurCodeMLP only produces MLP files. SurCode MLP willautomatically add an .mlp extension to your file name,

unless it sees a previously entered .___-type extension.Do not to change this unless you specifically want adifferent extension. Many programs (including MinnetonkaAudios discWelder CHROME) look for the .mlp extensionwhen authoring.

2.3 Select A DestinationClick on the Destination button (under the SurCodeLogo) to bring up the screen for Select A File (see Figure2-2).

Figure 2-2Browse in the Save in window (by clicking on the arrow

button on the right side of the window) to select the folder or volume where you wish to save your MLP file, then enter

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a suitable name for the MLP file in the File name window.After clicking the Save button, the MLP file name will bedisplayed in the SurCode MLP title bar.

2.4 Select Files To Encode

Clicking on the Channel Name button (Left Front, RightFront, etc.) opens up a browse window, where you canselect the soundfiles you wish to enter in the selectedchannel (enter the left soundfile into the Left Front

channel, etc.) Continue entering soundfiles into eachchannel that you have source soundfiles for.

2.5 Press The Encode Button

When all the source soundfiles have been entered into their respective channels, press the Encode button in the lower-left side of the screen. SurCode MLP will encode your files,automatically setting the options and assignments to thedefault values based on industry standards.

2.6 Listen To The MLP File

You can check the encoded file by playing it back using thetransport controls in the lower right side of the screen (itwill have been verified for accuracy automatically). Selectthe Destination button under the controls, and pressPlay.

2.7 Other Options

The remainder of this manual describes encoding optionsand features that may be used to customize the encoding

process.

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3 Main ScreenThe SurCode MLP Main Screen is where your soundfileswill go to be encoded or played (see Figure 3-1).

Figure 3-1

3.1 Menu BarThis is a standard Windows menu bar, with the followingcomponents:

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3.1.1 Setup

This is where you will find the standard Windowscommands New, Open, Save, Save As, Recent

Projects, and Exit. If these commands are unfamiliar toyou, please consult the Windows Manual.

3.1.2 Options

The Encoder Options section found in this menu bar selection is important in setting the parameters for encoding

if you decide to use settings other than the default parameters (see Figure 3-2).

Figure 3-2Also found in this menu bar selection is Device Options,which allows you to set the devices for audio playback (seethe Options chapter).

3.1.3 HelpThis is a standard Windows menu bar selection, with Sur-Code Help (which opens the SurCode MLP Manual inHTML form), SurCode Web Site (which connects you tothe Minnetonka Audio Software web site via your Internet

connection), and About SurCode MLP (which has ver-sion, copyright, and contact information).

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3.2 DestinationThe Destination button allows you to set up the encodedfile destination folder or volume, as well as the encoded filename (see the Getting Started chapter).

3.3 Channel AssignmentThis drop-down list allows you to specify the type of chan-nel assignment combination that fits your project. There are21 combinations of channel assignment/group assignment,and you may choose the type of combination for your

project (see Table 3 in Appendix A - Tables and theChannel Assignment chapter), or SurCode MLP willchose the combination automatically based on the channelsoundfiles you enter (automatic combination selection is thedefault setting).

3.4 SoundfilesThis set of browsable windows with corresponding channel

buttons (Lf, Rf, Center, LFE, Ls, and Rs) is where you willenter the soundfiles for these channels (see the Soundfileschapter).

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3.8 Mute/SoloThese buttons Mute (M) or Solo (S) the six individual chan-nels during playback (see Figure 3-4).

Figure 3-4

3.9 Channel NameThese are the Browse for Soundfile buttons for the 5.1

Surround channels (see Figure 3-4). When a Channel Name button is pressed, a browse window opens for soundfileselection for that channel. Double-clicking on a soundfile

places it into that channels window (see the Soundfileschapter)

3.10 Encode SectionThis section contains the Encode button, the Stop but-ton , the Start Time Set and Reset buttons, and the End Time

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Set and Reset buttons, as well as the Start and End Timewindows (see the Encode Section chapter).

3.11 Playback Section

This section contains the playback transport controls, the playback location (time) indicator, and the Source/Destina-tion selector (see the Playback Section chapter).

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Figure 4-2

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4.2.1 Downmix Section

This section allows you to choose whether or not to includea downmix in your MLP encoded stream, and what the

individual channel parameters within that downmix will be(see the Downmix chapter).

4.2.2 ReBit Section

This section allows you to reduce the bit-depth of any or allof the six channels in extreme cases where encoding within

the 9.6Mbps DVD data rate is not possible without alteringthe source files (see the ReBit chapter).

4.2.3 Verification/Playback Section

This section allows you to specify two optional modes of verification (standard verification is automatic and non-defeatable), and one of two types of soundfile playback (seethe Verification/Playback chapter).

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5 Soundfiles

5.1 Entering SoundfilesEntering your source soundfiles in SurCode MLP is veryeasy - simply click on the Channel Name button (see Fig-ure 5-1) and browse through the available volumes and filesfor the soundfiles you wish to encode (see Figure 5-2). Thendouble-click on the soundfile that corresponds to theselected channel name (i.e., select the Left soundfile for theLeft Front window).

Figure 5-1Enter all the rest of your soundfiles in their respective win-dows by clicking on the Channel Name buttons and double-clicking the appropriate soundfiles to enter them. If you donot have soundfiles for some of the channels, simply leavethem blank. SurCode MLP will automatically re-configurethe Channel Assignment choices to reflect the channels thatare filled (see Section 5.4, Channel Assignment).

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Figure 5-2

5.2 Clearing SoundfilesTo clear a soundfile from a channel window, click on theChannel Clear button next to that channels window.

5.3 Channel Bit- and Sample-RatesSurCode MLP shows you the bit-rate and sample-rate infor-

mation for the channel soundfiles in the Bit/Sample Rateswindows. Standard digital audio numbering is followedhere, which is bit-rate number/sample-rate number.

5.4 Channel AssignmentThere are 21 combinations of Channel Assignments (see

Table 3 in Appendix A -Tables and the Channel Assign-ment chapter) involving two different Groups. This allowsyou to place channels with lower sample-rates in a secondgroup, as long as two conditions are met:

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1. The Group 2 channels must all have the same sample-rate (this is also true for Group 1).

2. The second groups sample-rate must be an even mul-

tiple of the first groups; for example, if Group 1 is at96kHz and Group 2 is at 48kHz, then Group 2 is exactlyone-half the sample-rate (Fs) of Group 1.

SurCode MLP automatically limits the choices of channel-to-group assignments to those applicable to the number anddesignation of channels that have soundfiles entered. For

example, if you place a soundfile in the Center channel,SurCode MLP will allow only the Group combinations witha C in the available choices.

Note: If you are using ONLY a Mono soundfile in a track, itMUST be assigned to the Center (C) channel (Channel

Assignment Option 0), not to the Left (or Right) channel.5.5 Channel Group IndicatorThese windows indicate which Group (1 or 2) the associ-ated channel is assigned to (see the Channel Assignmentchapter).

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6 Downmix

6.1 What Is Downmixing?

The purpose of downmixing is to allow consumers withoutsurround audio capabilities to listen to your surround mixesin stereo. Some producers include a separately-mixed stereotrack in the DVD-Audio disc, but this uses more disc space.SurCode MLP provides a simple solution to providing a 2-channel (stereo) downmix. The encoder includes lossless

matrixing, which can encode a two-channel downmix as alinear combination of the multi-channel mix and encode thisalongside the multi-channel version on the DVD-A disc.The advantage of this approach is that the producer canlisten to the downmix at the encoding stage with theknowledge that it will be delivered bit-for-bit to the end user at the decoding stage. Another advantage is that a two-channel-only playback device does not need to decode themulti-channel stream, and needs only to decode the stereo.

6.2 Downmix Defaults

SurCode MLP defaults to Downmix On, and to industrystandard downmix coefficient values (shown in Figure 6-1).To encode a downmix using values other than the defaults,you will need to specify the new values for each channel inthe Channel Coefficient windows. These coefficient valuescan be determined by listening to the surround mix on anaudio workstation or mixing console, blending the tracksinto a stereo mix, and determining the desired balance. Theresulting channel fader settings can then be applied to therespective Downmix Channel Coefficient settings directly

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in dB, as well as any phase (polarity) reversal and/or channel mutes.

Figure 6-1

6.3 Left/Right DownmixThis section, which is found in the Options Menu Bar section (Menu Bar > Options > Encoder Options) allowsyou to choose whether or not to include a downmix in your MLP encoded stream by clicking on the Downmix Select

checkbox (the default is On), and what the individualchannel coefficients within that downmix will be (seeFigure 6-1).

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6.3.1 Channel Coefficients

The Channel Coefficient values are entered into the LeftMix and Right Mix Channel Coefficient windows via the

up/down buttons (located next to the coefficient windows).These coefficients determine the relative levels (that is,relative to the levels of the source surround mix soundfiles)of each channel in the encoded stereo downmix, and theyare entered in decibels (dB). Decibel entry is effective

because the relative dB levels can be read directly fromaudio console or workstation channel fader settings. Therange of values for the channel coefficients is from (plus)6dB (increased gain) to minus infinity (maximumattenuation, or Off).

6.3.2 Channel Phase

The Channel Phase In/Out button (actually a 0/180 degree polarity button) reverses the phase (polarity) of theindividual channels. The 0 setting is in-phase, the outsetting is 180 degrees out-of-phase (reverse polarity).

6.3.3 Channel Mute

The Channel Mute (On/Off) button is useful for quicklyreducing the coefficient values down to minus infinity(Off) for alternate channel stereo assignment (i.e., Lf toLeft Mix, Rf to Right Mix; and Ls to Left Mix, Rs to RightMix). The On/Off button toggles between Off and theOn value shown in the Channel Coefficient window.

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6.3.4 Restore Defaults

This button resets all downmix parameters to their defaultvalues (which are shown in Figure 6-1).

6.3.5 Downmix Clipping

The downmix process does NOT prevent clipping of thestereo output signal, because that may be the artistic intent.When clipping occurs, the signal is not clipped in the fullmulti-channel MLP stream (which continues to operate

losslessly) but in the DVD-Audio player. If the downmix isclipped, the file WILL encode (i.e. it is not a Fatal Error,which would cause the encoder to stop), but the Encode Logwill indicate that the downmix has Saturated. Verificationof this encoded file will fail, with the reason for failure inthe Verifier Log noted as Downmix Clipped. Saturationand Clipped are terms for the same thing.Note: Gain added in any of the Channel Coefficientwindows (the available gain is 6dB) will possibly clip thedownmix playback - use caution when adding gain, andalways listen to the encoded MLP file to make sure the

downmix is free of clipping (unless that is the artisticintention).

6.4 Downmix Parameters

The Downmix output is at the same sample-rate as thesoundfiles in Group 1, and it is always at 24-bit, even if thesource soundfiles are at 16- or 20-bit. The Downmix outputis also always in the stereo format.

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7 Channel AssignmentSurCode MLP allows the user the choice of defining thechannel-to-group assignments, or letting the program auto-

matically determine the assignments based on the userssoundfile entries (see the Soundfiles chapter). The avail-able combinations are shown in the Channel AssignmentOptions Window, which is activated by the Channel Assign-ment Options Pull-down button on the right side of theChannel Assignment Window (see Figure 7-1).

Figure 7-1

7.1 Why Use Groups?The reason for the assignment of channels into two groupsis the capability of mixing two different sample-rates (thesample-rate within a group must be the same for all chan-nels). For example, the Lf, Rf, and C channels may be at96kHz resolution in Group 1, and the Ls, Rs, and LFE chan-nels may be at 48kHz resolution in Group 2. However, the

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sample-rate for Group 2 must be an even multiple of thesample-rate in Group 1, for example Group 1=96kHz,Group 2=48kHz..Note: Channel bit-depths may be different within the twogroups.

7.2 Channel Assignments

DVD-Audio supports up to six channels in one of 21combinations of channel assignments based on number andtypes of channels (see Table 3 in Appendix A - Tables)

7.3 Assignment OptionsSurCode MLP will make the assignment option choice for you based on the channels you enter into the channel win-dows. This process is automatic.However, you may wish to set up the Group assignmentcombination manually, either after entering a single sound-file, or after all your soundfile entries are done. If you waituntil all your soundfiles are entered, the combinationoptions will be limited to the applicable choices. For exam-

ple, if the source soundfiles you have entered include Lf, Rf,LFE, and C channels, SurCode MLP will limit the optionchoices to those with these channels in the combination.This lessens the possibility of error in channel assignmentgroup combinations. Note that there will be channels in theavailable combination options that you have NOT entered(to allow further channel entry, if desired), but each of theoptions will include those channels already entered.Note: If you are using ONLY a Mono soundfile in a track, itMUST be assigned to the Center (C) channel (ChannelAssignment Option 0), not to the Left (or Right) channel.

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8 Encode SectionOnce the soundfiles have been placed (see the Soundfilechapter) and the encoded file destination specified (see the

Getting Started chapter), you are ready to encode thesoundfiles into an MLP stream, unless you wish to changethe defaults of any of the following:

1. The encoder options (see the Options chapter)

2. The downmix coefficients (see the Downmix chap-ter)

3. The channel assignment (see the Channel Assign-ment chapter)

If your project is ready to encode, simply press the StartEncode button (see Figure 8-1) and wait for the finishedMLP file.

Figure 8-1

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8.1 Encode Start and End TimeYou can encode the entire soundfile length (which is thedefault setting), or encode only a section of the soundfile byspecifying a different start and end time in the Start Timeand End Time windows (see the Caution below).Additionally, you can set the encode Start or End times atthe current playback location with the Set buttons (see Fig-ure 8-1).If you want the soundfile encode to start at 00:00:00.00(which is the Start Time default), you can press the Reset

button next to the Start Time window. Pressing the Reset button next to the End Time window resets the End Time tothe length of the soundfiles (which is the End Time default).Note: Time location in SurCode MLP is numbered asHours: Minutes: Seconds. Fractions (hundredths).CAUTION:You can directly enter the time values in the Start Time andEnd Time windows; however, if you do so you will lose thethousandths decimal place, which is not shown in thewindows (00:00:00.000). This may result in a loss of sam-

ples at the start or end of the current project, depending onwhich window you edited by direct entry.

8.2 The Encode ButtonThis button starts the encoding process.

8.3 The Stop ButtonThis button stops the encoding process. This will result inan incomplete but playable MLP stream, which can be usedto test various settings in the encoder before committing toan entire soundfile encode (which can take a long time withlarge soundfiles and slow computers).

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9 Playback SectionSurCode MLP allows you to playback your soundfiles fromthe Source, or from the Destination. (see Figure 9-1).

Figure 9-1

9.1 Source/Destination SelectIf you chose Source with the Source/Destination Selectradio-style buttons, the imported source files are played

through the output devices selected in the Device Optionswindow (Menu Bar > Options > Device Options), followingthe selected track assignments (see the Options chapter).If you chose the Destination button, the DestinationMLP file is decoded and played. In addition, while playing

back the decoded MLP file, SurCode MLP will verify that

the file is a valid MLP stream (see the Verification/Play- back Section chapter). If the MLP stream is not valid, anerror message is generated.

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9.2 Transport ControlsThe control buttons, from left to right, are: Return To Zero(the start of the soundfile), Rewind, Fast Forward, Stop, andPlay. These function similarly to tape transport controls.

9.3 Current LocationThis windows indicates the current location of the playback in Hours: Minutes: Seconds only (no fractions of a second).

Note: Time location in SurCode MLP is numbered asHours: Minutes: Seconds. Fractions (hundredths).

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10 Verification/Playback Section

10.1 Verify SelectSurCode MLP automatically verifies that the encoded MLPstream is identical to the source files. In the Encoder Options section (Menu Bar > Options > Encoder Options),there are two available modes in the Verify Select section,selectable with radio-style buttons (see Figure 10-1):

1. Verify after encoding is complete (the default set-

ting), or:2. Verify on-the-fly while encoding.

The Verify-on-the-fly mode is faster than the Verify after encoding is complete, but is useful mainly for test puposes,

becuase it verifies only the data in the buffer, not the actualdata written to disc. The Verify after encoding is completemode is the only true bit-for-bit verification between thesource soundfiles and the disc data.

Figure 10-1

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10.2 Write Decoded File SelectAdditionally, SurCode MLP can write decoded Wave fileswhile verifying, for later quality reference. These Wave filesare written as decoded stereo pairs (Lf/Rf, C/LFE, Ls/Rs,Downmix) that are placed in the same folder as the MLPDestination (encoded) file. These files can be imported by asound editing program, including the program that createdthe source soundfiles, for waveform quality comparison if desired. Simply check the Write decoded wave files whileverifying box (see Figure 10-1).

10.3 Playback SelectSurcode MLP allows you to playback the decoded MLPstream in one of two modes (also see the Playback Sec-tion chapter):

1. Playback individual channels mode (the multi-channel MLP stream), or:

2. Playback downmix mode (the stereo MLP down-mix).

The selection is made by pressing the appropriate radio-style button (shown in figure 10-1).

Note: Playback of the MLP stream is possible only after encoding.

10.4 MLP LogsA feature of SurCode MLP is the Encode Log (see theIntroduction chapter) generated by each encode pass.There is also a Verifier Log generated by SurCode MLPafter the Verify stage.

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11 ReBit (Bit-Depth Reduction)

11.1 Why Is Bit-Depth Reduction Needed?In certain rare cases of highly un-correlated source materialor very large source bandwidth requirements (for example,six channels of completely random noise at 24-bit, 96kHzresolution), the MLP process cannot pack the original chan-nel data into the 9.6Mbps maximum data bandwidth of theDVD-Audio specification and remain Lossless. In thesecases, SurCode MLP will generate an error message andabort the encoding process at the point the material failed toencode properly (see Figure 11-1).

Figure 11-1The result is that the original tracks themselves must bealtered BEFORE encoding, to enable SurCode MLP to pack the material into an MLP stream. There are several ways todo this alteration:

1. Reduce the bit-depth of one or more channels, such asfrom 24-bit to 22-bit.

2. Filter one channels frequency bandwidth to low-passonly, or LFE (Low Frequency Effect, commonly calledthe Subwoofer channel) if this has not been donealready as part of the 5.1 Surround mix process. Note

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that the LFE channel is frequency-limited in the 5.1 Sur-round mode, but other surround modes may use six full-range channels (6.0 Surround, for example).

3. Reduce the audio bandwidth; for example, by filter-ing information above an arbitrary frequency, such as40kHz when sampling at 96kHz.

4. Use Minnetonka Audios exclusive feature calledReBit, which can manually or automatically reducethe effective bit-depth on a per-channel basis from

within SurCode MLP.All of these options will increase the amount of compres-sion that SurCode MLP can achieve, thus increasing the

playing time or reducing the peak data rate. However, onlyone of these choices works within SurCode MLP: ReBit.

11.2 Why Is SurCode MLPs ReBit Needed?Minnetonka Audio designed SurCode MLP to be able to

process all cases of highly un-correlated source material or very large source bandwidth requirements from within the

program using ReBit, for three reasons:

1. To save the time necessary to export the originalmaterial to a separate program for reducing bit-depth,frequency bandwith, or both.

2. To eliminate the need for requesting the source mate-rials producers to do this process themselves.

3. To ensure that the changes made to the material aresufficient to allow the MLP process to encode the mate-rial without further changes (and to ensure that excess

bit-depth reduction is not done).

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11.3 How ReBit WorksThe ReBit process reduces the effective bit-depth of selected channels by resetting the Least-Significant Bits (or LSB - the 24th bit, the 23rd bit, etc.) to zero, either manu-ally or automatically, in 2-bit steps. This reduces the amountof data compression necessary to encode the channel, with-out reducing the actual number of bits (which is why this isknown as effective bit-depth reduction). The significanceof this is that if the DVD-A player has a 24-bit indicator,it will stay lit.ReBit is a lossy process, because it reduces the actual bit-depth resolution of one or more channels before encoding(the MLP encoding process itself remains Lossless). If thesource material has failed the encode process, the originalsoundfiles must be altered or be removed from the DVD-Audio disc. In these rare cases, ReBit is an effective solu-tion.Another consideration is that the ReBit process (in theAutomatic mode) affects the LFE channel first, and thenoccasionally the Ls/Rs channels, and typically by only 2-4

bits. The LFE channel is often frequency-limited in 5.1 sur-round playback to 120Hz low-pass, and the reduction of

effective bit-depth on this channel is very nearly inaudible.Likewise, the Surround channels are frequently reproduced

by less-than-full-bandwidth speakers, and the reduction of effective bit-depth on these channels is also nearly inaudi-

ble.

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11.4 The ReBit SectionTo enable the ReBit process, check the Reduction Select

box. (see Figure 11-1).

Figure 11-2

11.4.1 Manual Bit-Depth ReductionThere are two modes in ReBit - manual and automatic. If you wish to set the bit-depth reduction parameters manually,use the up-down buttons next to each of the individual chan-nel Reduction Amount windows. The most common prac-tice is to start by reducing the LFE channel bit-depth first,

because this change is usually inaudible due to LFE/Sub-woofer channel low-pass filtering during playback (in 5.1surround mode). Subsequent bit-depth reduction can be per-formed on the Surround channels (Ls and Rs) in 2-bit incre-ments if the LFE channel bit-depth reduction fails to reducethe data sufficiently to pass the encode process. Usually theLf, Rf, and C channels will not need to be reduced.

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11.4.2 Automatic Bit-Depth ReductionThe strength of ReBit is the ability to automatically reducethe data rate by following pre-set steps calculated to causethe least audible change to the source material. ReBit cyclesthrough effective bit-depth reduction and re-encoding stepsuntil the material passes the encode process - the bit-depthreduction goes no farther than necessary.To apply Automatic Bit-Depth Reduction, check the Auto-matic Reduction Select box, then click on the OK but-ton, and then the Encode button on the Main Screen.Note:The Automatic setting also re-configures each ChannelReduction window to the Maximum bit-depth reductionamount. You must enter the maximum number of bits youwant to reduce each channel by - ReBit will do nothing if the Reduction Amount Maximum windows all remain atzero. ReBit will fully reduce each channel by the enteredamount only if it is necessary. This allows you to set theeffective bit-depth from a 24-bit file down to a minimum of 16-bits (a setting of 8 in the Reduction Amount Maxi-mum window, i.e. 24 minus 8=16). For example, you couldset the Lf/Rf and Center Maximums to 2 and the rest of the

channel Maximums to 8, ensuring that the front and center channels would not be reduced below a minimum of 22-biteffective resolution, while the other 3 channels could bereduced down to a minimum of 16-bit effective resolution.

11.4.2.1 ReBit Step Order

In ReBit, there are 16 successive steps in the automatic pro-cess of resetting the Least Significant Bits (LSB) to zero,two bits at a time, with an encoding restart between eachstep - a failed encode will initiate the next LSB reset step.

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The sequence of automatic bit-depth reduction steps isshown in the table below.

Note: Effective bit-depth minimum is16-bits.

11.4.2.2 Time SavingsThe time saved by the ReBit Automatic mode can be sig-nificant, because the MLP encode process itself can be

Table 1: Effective Bit-Depth per Channel (24-bit files)

Step Lf Rf C Ls Rs LFE1 24 24 24 24 24 22

2 24 24 24 24 24 20

3 24 24 24 22 22 20

4 24 24 24 20 20 20

5 24 24 24 20 20 18

6 24 24 24 18 18 18

7 24 24 24 18 18 16

8 24 24 24 16 16 16

9 24 24 22 16 16 16

10 24 24 20 16 16 16

11 24 24 18 16 16 16

12 24 24 16 16 16 16

13 22 22 16 16 16 16

14 20 20 16 16 16 1615 18 18 16 16 16 16

16 16 16 16 16 16 16

Step Shaded Channels have been Bit-Depth Reduced

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time-consuming, depending on the amount of material andthe host computers speed and RAM. The ability to solvethe problem of highly un-correlated source material or verylarge source bandwidth requirements from within SurCodeMLP can save time as well as extended re-mastering. ReBitAutomatic eliminates the need to manually alter the mate-rial, re-encode, then repeat the alter/re-encode cycle until it

passes the encode process.

11.4.3 Worst-Case Scenario

In encode-failure testing, worst-case scenario source sound-files - consisting of six channels of 24-bit, 96kHz randomnoise, which failed the encode process immediately - wereused to step ReBit Automatic through the LSB resetsequence.With the Maximum channel coefficients set to8 (or a possible effective minimum of 16-bits), ReBit

went through eight steps before the random noise files passed the encode process. That translates into no change onthe Lf, Rf, and C channels, and an effective bit-depth in theLFE and Ls/Rs channels of 16-bits. The front and center channels retained their 24/96 resolution and the surroundand LFE channels were reduced to 16/96 resolution - not

ideal, but the random noise passed.An Encode Log is generated by Surcode MLP duringencoding, and the successive ReBit steps are shown in thislog. The log can be saved for further reference (see theIntroduction chapter).Most cases of music, or speech with music, will not proceed

through any significant number of processing steps, if any.SurCode MLPs ReBit is really a worst-case scenario prob-lem-solver - you very likely will never need it, but its goodto have if you do.

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Appendix A - Tables

41

12 Appendix A - Tables

12.1 Compression AmountsThe following table gives examples of the typical compres-sion that can be realized with different audio bit- and sam-

ple-rates,

12.2 DVD-A Playing TimeThe following table gives examples of playing times onDVD-Audio that can be obtained with different channel,

bit-rate, and sample-rate combinations.

Bit-Rate Sample-Rate Minimum Typical

16-bit 48kHz 0% 50%

20-bit 96kHz 40% 55%24-bit 96kHz 38% 52%

24-bit 192kHz 43% 50%

Table 1: Compression Amounts

Number Of Channels Bit-Rate Sample-Rate Play Time

6 Chan. 24-bit 96kHz 86 min.

5.1 Chan. 24-bit 96kHz 100 min.

2 Chan. 24-bit 192kHz 2 hours

2 Chan. 24-bit 96kHz 4 hours

2 Chan. 16-bit 44.1kHz 12 hours1 Chan. 16-bit 44.1kHz 25 hours

Table 2: DVD-A Playing Time

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Appendix A - Tables

42

12.3 Channel AssignmentsDVD-Audio supports up to six channels in one of 21 combi-nations of channel assignments.

# Ch. 0 Ch. 1 Ch. 2 Ch. 3 Ch. 4 Ch. 5 # InGrp. 1

# InGrp. 2

0 M 1 0

1 L R 2 0

2 Lf Rf S 2 1

3 Lf Rf Ls Rs 2 2

4 Lf Rf LFE 2 1

5 Lf Rf LFE S 2 2

6 Lf Rf LFE Ls Rs 2 3

7 Lf Rf C 2 1

8 Lf Rf C S 2 2

9 Lf Rf C Ls Rs 2 3

10 Lf Rf C LFE 2 2

11 Lf Rf C LFE S 2 3

12 Lf Rf C LFE Ls Rs 2 4

13 Lf Rf C S 3 1

14 Lf Rf C Ls Rs 3 215 Lf Rf C LFE 3 1

16 Lf Rf C LFE S 3 2

17 Lf Rf C LFE Ls Rs 3 3

18 Lf Rf Ls Rs LFE 4 1

19 Lf Rf Ls Rs C 4 1

20 Lf Rf Ls Rs C LFE 4 2

Group 1 Group 2

Table 3: Channel Assignments

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Appendix A - Tables

Table 3 Key: M= MonoL= stereo Left

R= stereo RightLf= Left frontRf= Right frontC= Center LFE= Low Frequency Effect (commonly called Subwoofer)S= Surround

Ls= Left surroundRs= Right surround

The DVD-Audio channel assignments 8 to 12 are almostidentical to the channel assignments 13 to 17, and differ only in the way the channels are grouped (the Center Chan-

nel changes Groups).

Note: The sample-rates of the channels in the two Groups must beeven multiples, i.e. 96kHz/48kHz, or 88.2kHz/44.1kHz.

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