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MegaVoice Audio Processing
Overview of MegaVoices
Bible Book Introductions
Audio processing for the MegaVoice is a multi-step process. Here's an
- Source recordings are made, frequently by missionaries on the field, or
by nationals. The quality of these source recordings may limit the
compression ratio used in the final encoding process by MegaVoice, so it's
important that these recordings be the highest quality possible--even though
they will later be sampled down to roughly "telephone quality" audio.
- Recordings are converted to WAV files by "chapter" or other desired
- WAV files are filtered, preparing their audio qualities for high
- WAV files are split into small files and named hierarchically,
corresponding to the three levels of forward/back buttons on the MegaVoice
- After final processing of WAV files, these are sent to MegaVoice for
- The compiled files are ready to be loaded on the Ambassador units.
- Ambassadors can be ordered from MegaVoice pre-loaded by project
- The compiled project files can be returned from MegaVoice, ready to
load on the Scribe from a computer, then loaded onto Ambassador units.
Now for the details.
NOTE: the procedures below should be considered as a
DRAFT version ("alpha" or "beta"), to be refined through testing and usage.
1. Sound Recordings
Made in the field....
2. Recordings Converted to WAV chapter files
Rip Audio Files
Using Creative Mediasource player, rip files from audio
Album Luke (book or major division on MegaVoice)
In Tools > Settings > Audio CD/Rip tab > Rip Format: Wav,
Mono, 44100 kHz, 16 Bits Per Sample
Recordings are placed in:
C:\My Music\Cabecar\Album directory (where Album name is specified above)
Resulting files are BIG (about 5MB per minute of
recording), so have lots of hard disk space available.
Using the ReName file utility
can be downloaded from
for ease of use, put a copy in each directory where you want
to use it
use F2 to go to Expert mode
locate an Album (book) directory, and rename files in
project numberdetermined by MegaVoiceuse zeros as placeholders
sequential number for purpose of this MegaVoice projectdetermines
order of major divisions on the player
cb = Cabecar
sequential numberingdetermines order tracks are played. Note that
if you have an intro section, numbering will not correspond to
chapter numbers in Bible
The above format is actually the format for chapter
titles in the final processed files, but it in the intermediate stage it
works well to label the entire chapters this way.
3. Filtering WAV files
Using NCH Swift Sound WavePad
I am using WavePad v 3.00 from NCH Swift Sound (http://nch.com.au/wavepad/index.html),
a program that sells for around $50-75. I already had this program on my
computer, so I thought I would see if it has the capabilities required for to
prepare files for the MegaVoice devices.
I am outlining in detail the procedures I am using to
prepare sound files for MegaVoice in order to confirm that they are adequate,
for myself and other team members here to follow, and even to offer as a viable
alternative to Adobe Audition if the results are in fact adequate. Potential
More cost efficient (15% of the cost of Audition)
Batch processing capabilities
batch script can be saved for reuse
reduces potential for human error
decreases time required
more efficient use of disk space (no intermediate files required)
(I will also note that Audacity will have Batch processing
available in its next release (1.3), and even has a built in Speech processing
script which appears to have similar parameters to the MegaVoice procedures.
This might provide another option in the future, but the current Beta release
1.3.0b is very unstable and useless at this point.)
Our source material was available on audio CD. This
material was ripped using Creative MediaSource v 3.20.79 to a file/directory
structure, saving the output as PCM wav 16-bit mono files sampled at 44.1 kHz.
Source files are saved to
File Names: 00000-Luk001-nfC001.wav for chapter 1
Output files (generated below) are placed in
Batch Processing in WavePad
Batch processing in WavePad is set up as a 3-step process
in the interface to specify: 1) files to to be processed, 2) batch commands, 3)
output format and directory.
The Batch processor can be accessed in at least 3 ways: an
icon on the icon bar, a command link on the left-hand command bar, and under the
Tools menu (see screen shot). Any of these goes directly to Step 1.
Batch Converter Step 1:
Use the Add Files button (the Add Folder button
appears to have a bug in it and does not end up processing any filessee
Batch Converter Step 2:
Browse up to
C:\My Music and locate Speech8:
<<NOTE: later save in subdirectory with filesfor
convenience and so can reproduce same settings>>
Initially, the commands shown must be added using the
Add button. The settings shown are set by double-clicking the
Command or clicking its Settings button. However, see below regarding
the Equalizer settings.
The Commands can be re-ordered by dragging and dropping the
Commands in the list.
After the commands have been set up, they can be saved for
reuse by clicking Save As and specifying an appropriate name. Note the
location where this file is saved for future reference. These files can also be
transferred to others for their use. In the future, the saved set of commands
is loaded by opening the saved batch file.
Click Next when Commands are properly entered.
I have used Auto Trim to take off leading and trailing
silences in the source files so that appropriate silences could then be added on
using MegaVoice standards. I also put Noise Reduction ahead of these steps so
that the Auto Trim command would function properly.
I have inserted Amplify in 2 places since the Normalize
doesn't seem to be working well. Depending on the level of the source file, 90%
x 90% may work well, or 80% x 80%.
The Equalizer settings appear to be saved on a
program-level basis, and are NOT retained by the Batch Script File. Therefore,
these settings most be opened and set the first time through, and should be
verified prior to re-running any batch procedure. Opening the Equalizer
Settings (by double-clicking the Equalizer Command line, or by clicking
the Settings button) reveals:
The HighPass setting is used with the Logarithmic
Mode. While the settings are displayed graphically, the actual parameters must
also be reviewed. These are revealed by clicking on the Settings button:
The Pass Frequency determines the top bend point,
and subtracting the Slope Length determines the bottom bend point. The
Amplitude determines the percentage of the filter below the bottom bend
point. Thus the example above runs at 33% from 0 up to 100 Hz, then slopes up
to 2000 Hz where it reaches 100%.
I have tried a higher pass frequency using my source
materials (such as 4000 following MegaVoice's example in Step 6, Figure 5), but
the results did not seem as clear audibly.
Batch Converter Step 3:
Here the format is chosen as .wav and the output
folder is specified. In addition, the Format Options button reveals the
following options for wav files:
The Format and Attributes must be chosen as
PCM and 8.00 kHz, 16 Bit, Mono, and these settings can be saved as MegaVoice
for future use using the Save As button (so in the future, this option
will show up in the Name list).
Processing time seems quite reasonable, and results appear
to be good. Batch processing of the book of Genesis took 8 minutes on a 5(?)
year old 1.4 GHz AMD Athlon machine with 512 MB RAM.
4. WAV files split and named hierarchically
The open source audio editing program Audacity (available at
provides the best capabilities for splitting the filtered WAV files into the
smaller segments that correspond to each press of the forward/back button keys.
Use of version 1.2.x has proven stable and is described below. (Early Beta
versions proved unstable, but also promise the possibility of batch processing
in the future, which could potentially replace use of WavePad above.)
There are two methods for splitting speech files, while music files are split
- Speech files can be manually tagged for splitting at actual paragraph
breaks using a transcript of the recording. Expected processing time
is 3 times actual play time.
- Speech files can be tagged for splitting using a semi-batch process by
identifying natural breaks in the speech patterns in the recording.
Expected processing time is less than actual play time.
- Music files can be split automatically based on approximately 20 second
The procedures below are for method #2, but could be adapted for method #1.
Overview of processing:
- load chapter file into Audacity
- use Analyze > Silence Finder to identify potential breaks in the
- different settings may be needed in different parts of the chapter
depending on the nature of the text or due to changes in readers
- resulting files must be < 1MB in size, which equates to about 1 min
play time. Therefore, segments must be < 50 seconds.
- to be most useful, segments should be about 20 seconds
- beginning of chapter must be tagged so that a file will be created
- use File > Export Labels to save the tags for potential later
- use File > Export Multiple along with careful naming schema to
split the file out into numerous files according to the targeted
- some renaming of files using the rename utility is still required
- a final tidying filtering pass is used. Resulting files are ready
for upload to MegaVoice.
Details to follow...
Sample of WAV file naming structure:
00000-Luk001-nfC001.wav||chapter title ("chapter 1" + header if
00000-Luk001-nfC002.wav||chapter title - note that if introductory
material is included as "chapter 1" (above), then this file name "C002"
actually corresponds to Chapter 1 of the book.|
Note: every level of file must be present. If there is not a chapter
title, for instance, a 0.1 second silence file must be inserted with that name.
5. WAV files sent to MegaVoice
MegaVoice should be contacted in advance of the above processing so that the
project can be put in their queue. While their actual processing
turnaround time can be quite rapid, they have a significant queue of projects to
be processed, and the lead time required may be several weeks or a more.
6. Compiled files ready to load on Ambassadors
Copyright (c) 2006-2008 Joe A. Friberg