Sonnox Fraunhofer Pro-Codec User Manual

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9.3 Codec Specifications

9 SPECIFICATIONS

doesn’t support the sample rate at any bit rate, the codec will default to AAC-LC at the
closest bit rate.

To illustrate this behaviour, consider a stereo session at 48 kHz with three codecs

selected. If the session configuration is changed to mono at 32 kHz, the plug-in will make
the following codec selections:

Selected Codecs

Substituted Codecs

Reason

Session

Session

Stereo 48 kHz

Mono 32 kHz

Codec 1

HE-AAC 128 kbps

HE-AAC 56 kbps

HE-AAC 128 kbps not
supported at 32 kHz.

Codec 2

HE-AAC v2 56 kbps

AAC-LC 56 kbps

HE-AAC v2 is stereo
only.

Codec 3

HD-AAC 160 kbps

AAC-LC 96kbps

HD-AAC

not sup-

ported at 32 kHz.

To avoid these problems after changing the session configuration, it is advisable when

using affected host applications to press

PLAY, then STOP, before instantiating the

plug-in or loading a plug-in Preset. This will ensure that session sample rate and channel
configuration data are flushed through the plug-in correctly.

It is also advisable to save Presets for the plug-in at a variety of session sample rates and
channel configurations.

To illustrate this further, consider the following examples. WaveLab 7 is used in these

examples because it has the powerful ability to easily select and play files with different
sample rates. Several other applications exhibit the same behaviour.

Example 1: Different session sample rates and compatible codec bit rates

WaveLab 7 is an example of an application that only provides session configuration

information to a plug-in when there is an active audio data stream (i.e. the transport is set
to play).

Using WaveLab 7, make three mono 24 bit wav files available via the tabbed windows in
the audio file workspace. One is 32 kHz, and is currently selected and playing. The
unselected tabs have a 44.1 kHz wav file and a 22.05 kHz wav file available.

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