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4.8.2 Example 2. Different session sample rates and incompatible codec bitrates
Using WaveLab 7, set up two wav files in the tabbed windows in the audio file workspace.
One is stereo 24-bit 32kHz, and is currently selected and playing. The unselected tab has a
stereo 24-bit 48kHz wav file associated with it.
A Sonnox Fraunhofer Pro-Codec is instantiated. As the HD-AAC codec does not support
32kHz, the HD-AAC option does not appear in the codec selection window.
The transport is stopped, and the 48kHz file is selected. The user now tries to select the HD-
AAC codec, but it is still not available as an option. After the transport is set to play, the
codec can be changed to HD-AAC. The file plays normally and the plug-in and codec
perform normally.
The transport is stopped, and the 32kHz file is re-selected. Now, if the transport is set to play,
the codec will receive invalid audio data, and the plug-in will substitute an AAC-LC codec.
Quit and re-start WaveLab 7. Select a 32kHz wav but do not press PLAY. Instantiate the Pro-
Codec. At this moment the plug-in has not picked up the correct session data because
WaveLab has not been set to play. The plug-in has been defaulted to 44.1kHz. Note it is
possible now to select HD-AAC but, if this is done, the plug-in will substitute an AAC-LC
when PLAY is pressed (as above).
Now try to load a Preset saved from a 32kHz session. A warning message indicates that there
is an incompatible sample rate (the plug-in thinks it is 44.1kHz). To progress, press PLAY,
then STOP, and then load the Preset.
4.8.3 Summary
These complications arise mostly when low sample rates (32kHz) are combined with low
bitrate codecs; or when high sample rates are combined with high bitrates.
Generally Pro Tools, Logic, Cubase, and Nuendo are among the hosts that are immune to this
behaviour, but Sequoia, Samplitude and WaveLab are examples of hosts that can exhibit
these issues.
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.