Sonnox Fraunhofer Codec Toolbox User Manual
Contents
1 Introduction.................................................................................................................................................. 1
2 Supported Codecs and Formats................................................................................................................ 2
3 Summary of Codec Features and Applications.........................................................................................3
4 Terminology................................................................................................................................................. 4
5 Codec Details............................................................................................................................................... 5
6 The Codec Toolbox Plug-In......................................................................................................................... 6
6.1.1 NMR Meter.................................................................................................................................... 8
6.1.2 Bit-stream OVERS Meter............................................................................................................... 9
6.1.3 Channel Configuration................................................................................................................. 10
6.1.4 Dither........................................................................................................................................... 10
6.1.5 Data Compression....................................................................................................................... 10
6.1.6 Internal Buffer Sizes..................................................................................................................... 11
6.2 Creating your Final Mix..................................................................................................................... 11
7 The Codec Toolbox Manager.................................................................................................................... 13
7.1 Folder Browser.................................................................................................................................. 14
7.1.1 Setting up a Root Folder.............................................................................................................. 14
7.1.2 Finding Audio Files on your System............................................................................................. 15
7.1.3 Supported File Types................................................................................................................... 16
7.2 File List............................................................................................................................................... 16
7.2.1 Selecting Multiple Files – Batch Processing................................................................................17
7.3 Encode-Decode Section.................................................................................................................... 18
7.3.1 Encoding...................................................................................................................................... 19
7.3.2 Dither........................................................................................................................................... 19
7.3.3 Decoding...................................................................................................................................... 20
7.4 Auditioning Audio Files in the Manager........................................................................................... 20
7.5 The Metadata Editor.......................................................................................................................... 21
7.5.1 Overview...................................................................................................................................... 21
7.5.2 Supported Tag Formats............................................................................................................... 23
7.5.3 Supported Tags............................................................................................................................ 24
7.5.4 Editing Text Tags.......................................................................................................................... 25
7.5.5 Adding Cover Art.......................................................................................................................... 25
7.5.6 Importing Tags from Another File................................................................................................. 26
7.5.7 Saving and Loading Metadata Presets........................................................................................27
7.5.8 The Metadata Lock Mechanism...................................................................................................29
8 Keyboard Shortcuts................................................................................................................................... 30
9 Workflow Example..................................................................................................................................... 31
10 Specifications.......................................................................................................................................... 32
10.1 Metadata Text Encoding.................................................................................................................. 32
10.2 Sample Rate and Bit Depth............................................................................................................. 33
10.3 Codec Sample Rate vs. Bit Rate..................................................................................................... 33
10.3.1 Sample Rate: 32 kHz................................................................................................................. 33
10.3.2 Sample Rate: 44.1 kHz.............................................................................................................. 35
10.3.3 Sample Rate: 48 kHz................................................................................................................. 38
11 Copyright and Acknowledgements........................................................................................................ 41
12 Commercial use of mp3 content............................................................................................................ 42
13 Supported Platforms............................................................................................................................... 43
14 System Requirements............................................................................................................................. 43
back to contents
1 Introduction
The Sonnox Fraunhofer Codec Toolbox is designed for real-time auditioning of audio signals by the
Fraunhofer codecs, in addition to offline decoding, encoding and metadata editing of the resulting
files.
Mixing engineers can produce compensated mixes optimised towards specific target codecs,
thereby ensuring maximum fidelity. Similarly, mastering engineers may audition material in the final
format, and produce compensated, optimised masters for final encoding and distribution.
The Codec Toolbox Plug-in provides an interface to choose from a range of codec types and
settings. When inserted on a DAW main output, the Toolbox plug-in allows real-time comparison
between the input signal and the encoded/decoded signal. The plug-in includes meters to indicate
input level and the presence of overloads caused by the encoding process. These will require
correction to ensure an optimised bit-stream level for the target codec. The NMR METER (Noiseto-Mask Ratio) will indicate the frequency range(s) where encoding artefacts and codec-induced
noise might be audible.
Having created your mix and bounced to WAV or AIFF, the Codec Toolbox Manager is where
offline encoding takes place, and where metadata can be added or edited. It is also possible to
decode previously compressed files to WAV or AIFF formats.
1
back to contents
2 Supported Codecs and Formats
Major codecs supported:
• MP3
• AAC-LC
• HE-AAC
• HE-AAC v2
• MPEG Surround
• Apple AAC (iTunes Plus; Mastered for iTunes) (Mac only)
Formats supported:
• Mono: MP3, AAC-LC, HE-AAC & HD-AAC
• Stereo: MP3, AAC-LC, HE-AAC, HE-AACv2 & HD-AAC,
• 5.1: AAC-LC, HE-AAC & HD-AAC, MPEG Surround
◦ L R C LFE Ls Rs (SMPTE/ITU)
2
back to contents
3 Summary of Codec Features and Applications
MP3
General purpose audio codec, compatible with most players.
Typical bit rate: 128 kbps (stereo)
AAC-LC (AAC Low Complexity)
High performance audio codec for excellent audio quality at low bit rates. Used for ISDB
television (Japan).
Typical bit rate: 128 kbps (stereo)
HE-AAC (High Efficiency AAC)
High performance audio codec for good quality at bit rates of 32–48 kbps per channel.
Used for XM Radio, mobile music downloads and Digital Radio Mondiale.
Typical bit rate: 64 kbps (stereo)
HE-AAC v2
High performance audio codec for good quality at bit rates of 16–24 kbps per channel.
Used for 3GPP music download, Digital Radio DAB+, and internet radio streaming to
mobile devices (e.g. iPhone).
Typical bit rate: 48 kbps (stereo)
HD-AAC (High Definition AAC)
Lossless audio codec with an optional lossy core. Used for music distribution and archival.
Typical bit rate: roughly half the bit rate of a 16-bit uncompressed WAV file.
Apple AAC
High performance audio codec for excellent audio quality at low bit rates. Used for Apple
iPod, iTunes etc.
Typical bit rate: 256 kbps VBR (stereo)
3
back to contents
4 Terminology
Bit rate
Number of bits transmitted or processed per unit of time. This is expressed here in kilobits
per second, or kbps.
CBR
Constant Bit Rate – bit rate remains the same for the duration of the audio signal
VBR
Variable Bit Rate – bit rate changes over time, based on the complexity of the signal. In this
case, the VBR value expressed is an average over the length of the file.
Encoder
In this context, an encoder converts an uncompressed LPCM audio stream into a smaller,
compressed format through the use of lossy compression (HD-AAC excluded).
Decoder
In this context, a decoder converts a compressed audio stream back into an uncompressed
LPCM audio stream.
Metadata
Categorical information about a file, such as the song Title, Artist and Album
Tag
One specific piece of metadata, such as the song Title
4
back to contents
5 Codec Details
Apple AAC iTunes Plus (Mastered for iTunes) (Mac only)
The addition of the Apple AAC codec allows real-time audition of files produced under the
Mastered for iTunes initiative that are destined for the iTunes store.
This codec is available for Mac computers only. It uses the same Apple codecs and re-samplers
that are used for the current iTunes Catalogue. It very specifically re-samples to 44.1 kHz if
necessary, and encodes as AAC-LC, 256 kbps, variable bit rate and maximum quality, which are
the settings used for the iTunes catalogue. For online audition, the signal is then resampled back
to the host DAW sample rate if necessary.
This option is available only for stereo configuration. There are no options to change the iTunes
codec settings because this would not be representative of the iTunes Plus standard. The Apple
codecs and re-samplers are components of the Mac OSX operating system, so can be upgraded
during an OSX update. On Windows computers, the closest approximation to the iTunes Plus
codec is the Fraunhofer AAC-LC codec set to VBR at 256kbps.
MPEG Surround (Fraunhofer)
MPEG Surround is a feature-rich open standard compression technique for multi-channel audio
signals. Operating on top of any core audio codec – including AAC, HE-AAC and MPEG Layer 2 –
the system provides a comprehensive feature set, including highest surround and stereo audio
quality, in addition to multi-channel support at stereo bit rates.
HD-AAC (Fraunhofer)
The HD-AAC codec from Fraunhofer has a very clever feature; the single compressed lossless file
includes a lossy core channel. It therefore acts as a lossless archival format, a lossless distribution
format for the masters, and a final playback format for both lossless and lossy decoders — and all
of this in a single file.
In the case of HD-AAC playback, if the decoder in your player has full HD-AAC capability, you will
be able to listen to a perfect replication of the original WAV file. However, the same HD-AAC file
will still play through a decoder that doesn’t have HD-AAC capability, and instead you will be
listening to the embedded lossy AAC channel.
5
back to contents
6 The Codec Toolbox Plug-In
The primary purpose of the Codec Toolbox Plug-In is to provide a way of monitoring your host
session material using the highly regarded Fraunhofer encoders, without the need for offline
processing.
By auditioning and comparing codecs in real-time, the plug-in enables you to make executive
decisions about the most appropriate codecs to use.
1. The INPUT SIGNAL METERS range from –40 to 0 dBFS, and are calibrated to provide
higher resolution in the range from –12 to 0 dBFS in order to be most useful for monitoring
final mix/master bus levels.
• The plug-in includes input sample peak metering and 16-bit clipping indication.
• Since the input signal is dithered and truncated to 16 bits, red clip lights indicate the
occurrence of hard clipping at the plug-in input.
• Metering options are provided for clip light Hold Time and to Force Channel
Configuration (see section 3.2). The options window is displayed by a right-click
inside the Input Meter area.
6
back to contents
2. Click inside the CODEC SELECTOR to reveal the codecs, modes and bit rates available
for the current sample rate and plug-in channel configuration. This allows fast selection of
different codec/setting combinations.
• The default codec settings are AAC-LC, 256 kbps, CBR (Constant Bit Rate).
• Selected codec settings are immediately reflected in the auditioned audio signal.
• Double-click a codec, mode or bit rate, or move the mouse cursor outside of the
selector to close the window.
• Selecting VBR (Variable Bit Rate) will re-generate the bit rate list. The available bit
rates may not be the same as for CBR bit rates. In this case, the Toolbox Plug-In will
provide the closest possible match to the previously selected CBR bit rate.
3. The NMR METER (Noise-to-Mask Ratio) provides an indication of the frequency areas
where the difference between the codec output and the original input might be audible.
4. The bit-stream OVERS meter monitors the peak sample level of the output of the decoder.
This provides an indication of the potential for signal overload when the encoded signal is
decoded in an end-user’s playback device.
5. The LAUNCH MANAGER button allows you to launch the Manager directly from within the
Plug-In.
6. The INPUT/CODEC button is used to smoothly switch the audition path of the plug-in
between the selected codec output and the input signal (dithered and truncated to 16-bits).
The signal being monitored is indicated by INPUT (blue) and CODEC (green).
• By default, this button is set to the CODEC position.
7. The STATUS PANEL displays additional information about the codec. Some Codecs
specify a particular sample rate, either for some or all bit rates they support. When one of
these configurations is selected, the STATUS PANEL will specify whether up-sampling or
down-sampling is being carried out by the plug-in.
Changing the session/project sample rate can change the available bit rates for the selected
codec. In this case, the closest-possible available bit rate will be selected.
Changing the channel configuration of the plug-in can change the codecs that are available to
select. If the previously selected codec is unavailable for the new channel configuration, the codec
settings will revert to default (AAC-LC, CBR, 256 kbps).
7
back to contents
6.1.1 NMR Meter
The NMR METER (Noise to Mask Ratio) provides an indication of the frequency areas where the
difference between the codec output and the original input might be audible.
All lossy codecs will produce a very slightly different output from their input. The very nature of a
perceptual coder is that this difference should be inaudible (i.e. masked by the output signal). You
can choose to trade off more data compression (and smaller files) against increased audibility of
artefacts and codec-induced noise. Theory states that this codec-induced noise should be
inaudible when the NMR indicator is green.
Under some circumstances (codec, frequency and input signal dependent) one or more of the
NMR LEDs will turn orange, indicating the frequency range where encoding artefacts and codecinduced noise might be audible. The listening environment, training and sensitivity of the listener’s
ears are also variable factors that must be taken into account.
It is possible to make very quick comparisons of a selection of different bit rates while auditioning
music and monitoring the NMR METER for such potential artefacts.
The NMR calculation is less accurate for parametric codecs (those that use enhancements such as
Parametric Stereo or Spectral Band Replication). HE-AAC and HE-AAC v2 use parametric
enhancements to achieve very high compression ratios. The NMR METER is still enabled for these
codecs, because it can still give an indication of the frequency areas that might require
examination.
Note that the NMR METER is not present if the selected codec is lossless (i.e. mp3-HD or HDAAC). The NMR meter is not valid or displayed for frequencies above 16 kHz, and is not supported
at a sample rate of 32 kHz.
NMR Frequency Ranges (to the nearest 1Hz)
8
back to contents
6.1.2 Bit-stream OVERS Meter
Any form of filtering can, under certain circumstances, increase the peak level of the signal. If your
input is hot, this can potentially produce overloads when the signal is decoded. This effect can be
very easily demonstrated with this plug-in.
The bit-stream OVERS meter can be used to monitor this potential for overload. The post-decoder
level is continually monitored, and the meter indicates levels over 0 dBFS. The bit-stream OVERS
clip LED will indicate that a clip event has occurred. Right-click inside the OVERS meter or clip
LED to select the told time for the clip light and meter peak indicator.
The mix level should be reduced by the amount required to avoid any overloads being indicated.
This may be done manually by lowering the overall mix level, or through use of a Limiter, for
example the Sonnox Oxford Limiter.
It is important to note that the indicated bit-stream OVERS metering and clip LED are provided as
a guide only. If a segment of audio is being looped or cycled, these maximum values are not
exactly repeatable from one loop to the next. Furthermore, in some host applications, repeatedly
rewinding to the beginning of the timeline/audio file will also not result in repeatable maximum
values. The discrepancies in both cases should be minor, and not all audio or codecs will suffer
this.
There is a highly technical reason for this, stemming from the difficulty of synchronizing the start
point of the buffer that is used to input data to the codecs.
9
back to contents
6.1.3 Channel Configuration
In most DAW hosts, the Codec Toolbox plug-in can automatically detect the number of channels
whether it is inserted on a mono, stereo or 5.1 surround track. Some hosts, however, have no
method of passing channel configuration information to the plug-in, which subsequently defaults to
a surround configuration.
To overcome this limitation, the Toolbox plug-in provides an independent method to force the
channel configuration of the plug-in to match that of the host. The options window is displayed by a
right-click inside the Input Meter area. These options are only available when the plug-in is
instantiated on a six-channel track, or on mono and stereo tracks in host DAWs where they are
required.
6.1.4 Dither
The encoders in the plug-in will accept an input signal with greater than 16-bit precision, but in
such cases the signal will be dithered and truncated to 16-bits prior to the encoding process.
The plug-in will not introduce dither at the 16-bit level if the input to the plug-in has been already
been dithered and truncated to 16-bits.
6.1.5 Data Compression
All of the available codecs compress an audio data bit-stream. Different codecs compress using
different algorithms, and will compress to very different degrees.
HE-AAC is optimized for the best quality at very low bit rates, and will produce very small files
(potentially around one hundredth of the input file size). Lossless encoders, in contrast, are not so
effective at compressing data, and will produce files that are around half the size of the input. The
familiar mp3 codecs typically produce compression factors of around 12.
Remember that using perceptual coding is always a trade-off between more accurate reproduction
of the original signal and a higher compression ratio and smaller files.
10
back to contents
6.1.6 Internal Buffer Sizes
For most codecs, the plug-in uses internal buffer sizes of 1024 samples for up to 48kHz operation
and 2048 samples for 48kHz. We recommend that the buffer sizes of the sound card, and thus of
the host application, are set to match these figures. Buffer sizes for the HE-AAC and HE-AAC v2
codecs are twice these figures (so 2048 samples for up to 48kHz operation).
The plug-in runs most efficiently and smoothly when supplied with sample buffers of 1024 samples
or multiples thereof. Smaller buffer sizes than 1024 samples can cause CPU spiking, which
different hosts may have a different tolerance to.
6.2 Creating your Final Mix
When working on finalising your mix or master processing, insert the Toolbox plug-in as the last
insert on your master output.
The Toolbox plug-in should be placed after your final limiter and dithering processor.
Use the NMR METER to help assess the areas of your mix that may be affected by the effects of
lossy compression. You may adjust areas of your mix, or adjust your Codec, Mode and Bit Rate
until you find a suitable balance between audio quality and amount of data compression.
(Remember, lower bit rates equate to greater data compression).
Play your mix or master from start to finish.
It is important to pay attention to the bit-stream OVERS meter. If this meter registers greater than 0
dBFS (red), it indicates that your mix or master has the potential to clip the DAC of the end-user’s
playback device, leading to undesirable distortion.
The sound of hard or soft clipping can be desirable for certain programme material. However in
such cases, it is much wiser to impart this desired sound by using a suitable clipping processor
prior to your final dither processing. This will ensure sonic consistency across various playback
devices.
To accommodate for bit-stream OVERS, simply reduce signal level prior to your final dither
processing, by enough to prevent the Toolbox plug-in OVERS meter from registering greater than 0
dBFS.
11
back to contents
When you have decided on suitable codec settings, and optimised your mix/master levels
accordingly:
1. Bypass or disable the Codec Toolbox plug-in
2. Bounce to uncompressed WAV or AIFF and save the resulting file to your chosen folder.
3. Open the Codec Toolbox Manager. This can either be done by clicking the Manager icon at
the top right of the plug-in, or by opening the application directly from disk.
12
Loading...