Manual
Table Of Contents
- Introduction
- Supported Codecs and Formats
- The Sonnox Fraunhofer Pro-Codec
- Additional Information on Workflows
- Lossless Codecs (mp3-HD and HD-AAC)
- Description of Controls
- Presets and Project/Session Data Handling
- Preset Manager Toolbar
- Pro-Codec Signal and Control Flow Diagram
- Specifications
- Copyright and Acknowledgements
- Manual Revision History
- Platform Specific Supplement
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The FFT display shows the signal frequency content. The input signal is displayed in yellow,
whereas the red line indicates the spectral content of the difference signal of the selected
codec (ie. the difference between the input signal and the encoded/decoded output signal).
This is referred to as the DIFF signal.
Alternating between the CODEC and DIFF buttons on the output section allows monitoring
of the codec output or the audio that is removed by the encoding process.
The LOG-LIN button toggles the frequency scaling of the displayed graph between
logarithmic and linear.
It is possible to both scroll and zoom parameters in the display area:
• For frequency, use the left mouse button to scroll left and right, and zoom up and down.
• For level (dBs), use the right mouse button to scroll up and down, and zoom left and right.
For a stereo signal the LEFT, RIGHT or SUM can be selected for display.
3.3.1 The NMR indicator
Also featured in the FFT display is the NMR indicator line, predominantly green in the
screenshot on the previous page, which provides an indication of the frequency areas where
the difference between the codec output and the original input might be audible. The NMR
indicator can be disabled by clicking on the NMR button (above the display).
All lossy codecs will produce a very slightly different output from their input. Sometimes, if
you listen to the difference signal it can sound significant; however, the very nature of a
perceptual coder is that this difference signal should be inaudible (ie. 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) this NMR line turns red (see
right hand side of FFT display on previous page), indicating that the induced noise is possibly
audible. The training and sensitivity of the listener’s ears is also an obvious and variable
factor to take into account.
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