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PostPosted: Sat Sep 12, 2009 10:34 pm 
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Encoding MLP Streams for DVD-Audio (using SurCode MLP)

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SOFTWARE REQUIRED

NOTE: There is currently NO FREE SOFTWARE available to encode MLP audio audio streams for surround sound playback. All software listed below is commercial software.



FILE FORMATS and NAMING CONVENTIONS

Music on DVD-Audio discs is created with files at various bit-rates, but most common bit-rates are 24-bits/48,000Hz (a.k.a. "24/48") and 24-bits/96,000Hz (a.k.a. "24/96"). MLP encoders 'encapsulate' the data of many files into one 'stream' file meeting the requirement of DVD-Audio specifications. The files you use to encode these audio streams should be prepared to meet this standard. Here is a general run-down of requirements for your .wav files, and how your individual mono .wav files should be prepared.

  • 1 or more mono .wav, .aif or .aiff files are required.
    NOTE: Only .wav files are mentioned for the purpose of this guide.
  • SurCode MLP encoders will accept up to 6 files (Lf, Rf, C, LFE, Ls, Rs)
  • Individual mono .wav files should all be of equal length and bit-depth
  • For ease of authoring, individual mono .wav files intended for authoring within a single DVD-Audio disc should be saved at the same bit-depth and frequency rate, such as 24/48 (24-bits, 48,000Hz) or 24/96 (24-bits, 96,000Hz). There are exceptions to this but they are not covered in this guide.

  • Individual mono .wav files output from another program should be saved and named appropriately to make it easier to remember what you are working with. All files must have a unique name and a .wav extension
  • For compatibility with all programs, avoid using spaces in your directory names and your file names
  • Use a simple numbering method to keep your files in the order of channels to be encoded
  • Here is an example list of 6 files that will be encoded:
    1. 01_Audio_2496_00.wav (Front Left)
    2. 01_Audio_2496_01.wav (Front Right)
    3. 01_Audio_2496_02.wav (Center)
    4. 01_Audio_2496_03.wav (LFE)
    5. 01_Audio_2496_04.wav (Surround Left)
    6. 01_Audio_2496_05.wav (Surround Right)
    -or-
    1. 01_Audio_2496_FL.wav
    2. 01_Audio_2496_FR.wav
    3. 01_Audio_2496_C.wav
    4. 01_Audio_2496_LFE.wav
    5. 01_Audio_2496_SL.wav
    6. 01_Audio_2496_SL.wav
  • There are 6 files in a normal 5.1 audio stream, one for each playback channel, however, you can choose to not use the LFE channel and only have 5 files. In this case you should still use the naming convention of *_04.wav and *_05.wav (or *_SL.wav and *_SR.wav) for the rear channels (if you don't understand why, don't worry about it. You'll understand later!)
  • You can encode a 'Quad' MLP stream by loading only the 4 required channels, FL/FR/SL/SR. Likewise, you can encode a 3-channel "front only" MLP stream by loading only the FL/C/FR channels. With SurCode MLP Encoder you can create MLP streams consisting of anything from "1-channel mono" in the Center channel only, up to 5.1 channel surround

    NOTE: Different programs will automatically output different filename formats similar to those shown in the example lists above. Some programs start output at number 0 thru number 5, others start output at number 1 thru number 6. It's up to you to make sure they're named properly for each individual channel. While you're outputting your files from the other program, remember to try avoiding the use of spaces and special characters. If your program does not include the "_" underscore character before the channel identification in the file name, it's a good idea to include the "_" underscore as the last character of your output file name (like "01_Audio_2496_.mlp") so that your files are easier to read and locate by filename alone! (Steinberg Nuendo is one such program that does not append the "_" underscore character before appending the channel identification prefix to the filename)


THE ENCODING PROCESS

The MLP encoding process is quite simple, however, for proper encoding the MLP encoding process requires a few extra steps compared to the steps required to encode DTS streams. This guide was written using Minnetonka's SurCode MLP Encoder. Additional help is available in the manuals provided with the purchased software.

Screenshot of SurCode MLP Encoder:


  1. Click the [Left Front...] button, locate and select your mono .wav file for the Left Front channel, then click the [Open] button
  2. Click the [Right Front...] button, locate and select your mono .wav file for the Right Front channel, then click the [Open] button
  3. Click the [Center...] button, locate and select your mono .wav file for the Center channel, then click the [Open] button
  4. Click the [SubBass LFE...] button, locate and select your mono .wav file for the LFE channel, then click the [Open] button
    NOTE: If you choose to NOT use the LFE channel, do not load this file! If you have already loaded the file, but the .wav file contains no audio, you can click the [C] button (directly to the right of the filename field) to clear the selection. It is suggested to leave this filename field blank if you do not have audio data in the LFE channel so that more bit data can be allocated to the remaining channels (this is exclusive to MLP encoding)
    NOTE: If you are NOT encoding with an LFE channel, see step 8 below for selecting the proper [Channel Assignment] grouping!
  5. Click the [Left Surr...] button, locate and select your mono .wav file for the Left Surround channel, then click the [Open] button
  6. Click the [Right Surr...] button, locate and select your mono .wav file for the Right Surround channel, then click the [Open] button
  7. Click the [Destination...] button, then locate a directory or folder to save your output file.
    • In the [File name] field, enter a name for the output file, identifying it as a MLP or DVD-Audio file and ending in ".mlp", such as "01_Audio_2448_DVD-A.mlp" (try to remember to not use spaces or special characters)
    • The [Save as type] drop-down is automatically set on [MLP Encoded Files (*.mlp) and cannot be changed]
    • Click the [Save] button

  8. Use the [Channel Assignment] drop-down to set the channel grouping.
    • Channel Assignment groups allocate data in groups (or pairs) of channels
    • Available channel groups will change depending on the frequency rate of your mono files. Not all groups are available for all frequency rates. Higher frequency rates result in less available channel grouping assignments
    • Select the proper [Channel Assignment] group for the type of encoding. Here is a screen-shot of all available channel groups within the DVD-Audio specification:
    • If you are NOT encoding with the LFE channel, then you should select the group combination labeled: [(Group 1) Lf, Rf, (Group 2) C, Ls, Rs] ... The LFE button should become un-available. This is how you know that you'll be re-allocating the remaining available data NOT used for the LFE channel, and allocating it towards the other channels

      Example of proper [Channel Assignment] group without LFE Channel:

  9. If you are ready to encode, press the [Encode] button!
    • To encode the entire set of files from start to end, make sure the "Start:" time is set to 00:00:00.00 and the "End:" time is set to the ending time of the file(s).
    • To reset the "Start:" or "End:" time, press the [R] button to the right of the appropriate time field
    • To encode only a portion of the files (such as a single track from a full-length CD) you can optionally set the "Start:" and "End:" times by typing in the appropriate time value. In this scenerio, be sure to not miss any samples by always including the same sample in the "End:" time when you set the next "Start:" time. For example, if Song 1 starts at 00:00:00 and ends at 00:04:55.99, then the next song (Song 2) would start at 00:04:55.99 and end at a later time such as 00:09:22.49 ... then the next song (Song 3) would start at 00:09:22.49 and end at a later time (and so on).
    • If you have already setup your [Device Options] (10.2 below) then you can listen to a all-channels preview to select the correct time for starting or ending an encoding. While listening, press the [S] button to the right of the "Start:" or "End:" fields to set the time of that field
    • If you are encoding individual songs from a full-length CD (or from files loaded that include multiple songs) then you MUST change the destination song name BEFORE pressing the [Encode] button, otherwise your previously encoded material will be overwritten!

  10. To setup the [Device Options] or [Encoder Options], click [Options] from the top menu

    • 10.2: [Device Options]: This area is where you setup the Playback Options related to your soundcard. Some soundcards do not properly expose their output channels and therefore cannot be used to playback the encoded/saved output file.
      • Set the [L/R] option to use your Front Left and Front Rear speaker channels
      • Set the [LR/RR] option to use your Surround Left and Surround Right speaker channels
      • Set the [C/LFE] option to use your Center and LFE speaker channels
      • Set the [Downmix] option to use your Front Left and Front Right speaker channels. The [Downmix] selection is used to preview a downmixed playback AFTER encoding has completed and is not meant for hearing surround output.
      • Click the [OK] button after changing any of these options
      • NOTE: Not all soundcards (Creative, for example) will expose the stereo pairs for surround playback. In some cases you can use alternate drivers for your soundcard to expose these pairs. If your card does not expose the stereo pairs, do not worry, you just won't be able to preview the encoded surround playback directly from SurCode, but you might still be able to listen to the "downmixed" encoding directly within SurCode
      • The "downmix" can only be played AFTER the encoding has completed.
      • To listen to the downmixed part of an .mlp encoded file, make sure (a) the encoder settings option is set to [X] Play back downmix, and (b) the main window is selected to play tne [X] Destination file
      • To listen to the surround mix BEFORE encoding, make sure the main window is selected to play the [X] Source

    • 10.3 thru 10.5: [Encoder Options]: This area is where you setup the encoding options for creating the MLP stream. Do not be intimidated by this screen!

      The [MLP Encode Options] window is divided into 3 sections: (a) Downmix, (b) Re-Bit, and (c) Verification and Playback

      • 10.3: Downmix:
        • The Downmix settings are individualized for the Left and Right stereo downmix channels
        • For the Left Downmix channel, the Right Front [On/Off] AND Right Surround [On/Off] options should always be set to [Off] (so that none of the Right Front or Right Surround signals end up in the downmixed Left channel
        • For the Right Downmix channel, the Left Front [On/Off] AND Left Surround [On/Off] options should always be set to [Off] (so that none of the Left Front or Left Surround signals end up in the downmixed Right channel
        • Enter the appropriate downmix coefficients for each channel
        • You might need to experiment, and each disc/song might require different downmix coefficients
        • Downmix coefficients can be reset to default by clicking the [Restore Defaults] button
        • The results of downmix coefficients can only be heard AFTER the encoding has completed. To listen to the downmix, make sure that the [Encoder Options] window is set to [X] Play Downmix, and that the Main window is set to play the [X] Destination file (a.k.a. the completed/encoded .mlp file)

        • If you choose to NOT include a downmix option for your DVD-Audio titles, simply un-check the "[X] Downmix" option.

      • 10.4: Re-Bit:
        • In general, the Re-Bit option is not used, however, for completeness purposes this guide discusses the basics of Re-Bit technology
        • Use the Re-Bit options at your own risk!
        • Re-Bit is a technique used to lower the available bits of one (or more) channel(s) and re-allocate those bits to the other encoded channels
        • Per-channel bit-depth allocation is exclusive to MLP encoding
        • Example Usage: If you have 6 mono files with 24-bit bit-depth, but the Center channel only has a limited amount of audio (wind noise, abstract non-important sounds, etc.) then you may decide to use less bits for the center channel by using Re-Bit to reduce the amount of bits for that channel
        • Example Usage: If you have 6 mono .wav files, all with 24-bit bit-depth, and you want to encode all tracks at 16-bits, then you would set each Re-Bit value to "-8".
          NOTE: This is NOT recommended! If you want to encode a 16-bit MLP track, then you should output your original mono .wav files at 16-bits!!!
        • Re-Bit will never reduce the available bit-depth for any channel to an amount below 16-bits


      • 10.5: Verification and Playback:
        • The options here are self-explanatory
        • It does not take any more or less time to verify while encoding than it does to verify after encoding
        • If you so desire, you can output an additional set of mono .wav files that represent the decoded playback files. (this is generally only used for technical purposes to verify that the decoded files will be the exact same as the original input files)

  11. The [ > ] playback button is used in the following manners:

      BEFORE ENCODING:
    • If you have setup your [Device Options] (10.2 above) then you can listen to a multi-channel preview before encoding by selecting the "[X] Source" option for playback. While listening the the pre-encoded source files, you can press the [S] button to the right of the "Start:" and "End:" time fields to set either of those fields to the current playback time.

      AFTER ENCODING:
    • If you have finished encoding a file AND you have setup the [Device Options] (10.2 above) for surround playback on your sound card, then you can choose the [Destination] option to playback your encoded stream in surround before importing the stream to a DVD authoring software
    • You can listen to a multi-channel encoded file OR a downmixed version of the encoded file by selecting the "[X] Destination" option.
    • To listen to the multi-channel encoded .mlp file, make sure the [Encoder Options] window is set to "[X} Play back individual channels"
    • To hear the downmixed version of the encoded .mlp file, make sure the [Encoder Options] window is set to "[X] Play back Downmix"

    • Use the Playback controls to perform the following operations:
      • [ |< ] Skip-to-Start of audio
      • [ << ] Rewind audio playback
      • [ >> ] Fast-Forward audio playback
      • [ [] ] Stop audio playback
      • [ > ] Play audio (or Resume Play)

  12. AFTER ENCODING you are presented with two dialogs:
    • The Encoding Log:

    • The "Encoding Log" shows extended information about the encoding process and output. Take special notice at the section after the words "Encoder initialisation: Succeeded". You might be presented with more lines if something went wrong during the encoding process.
    • Regardless of any errors that may occur, in most cases the last line will read "Encoder: encoding: succeeded!". This does NOT mean that you have encoded a DVD-Audio Compliant .mlp stream! (see "Verification Log" below!)

    • The Verification Log:

    • The "Verification Log" shows extended information about the verification process. Your encoded output file MUST be within specifications to ensure proper playback. If, for some reason or another, your file is NOT within proper specifications you might be presented with information in the Verification Log that explains why. In the scenerio above the last line reads "Verify: stream: failed". The reason is noted in the line above which reads "Verify: the downmix has clipped". In this situation you will need to lower the downmix coefficients found in the [Encoder Options] dialog, then re-encode until you achieve an output encoding without errors. (The last line of the Verify log should ALWAYS read "Verify: stream: passed."


AUTHORING A DVD-AUDIO DISC

Once you have finished encoding your files, you're ready to import your .mlp streams into your DVD-Audio authoring software, then author a DVD-Audio for playback on a Home Theater System capable of playing DVD-Audio discs. This guide does not cover the authoring or burning of DVD-Audio discs, so you'll need to visit another guide:

Guide: How to author a simple Music DVD-Audio with DiscWelder Chrome II (not available yet)

Similar Guide: Encoding DTS .WAV's for DTS CD's (Using SurCode DVD Pro)
Similar Guide: Encoding DTS Streams for DVD Authoring (using SurCode DVD Pro)

Click Here for Comments, Feedback & Discussion

Change History:
2009-09-12: Initial Guide Published

This Guide is Copyrighted © 2009, SurroundByUs.com


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