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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5.1 Auditioning Lossless Codecs
The two lossless codecs from Fraunhofer have 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, for example, if the decoder in your player has full HD-
AAC capability, you will be able to listen to 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 lossy embedded AAC channel.
5.1.1 HD-AAC (24-bit / 16-bit lossless)
It is possible to audition in real time the HD-AAC codec. If the HD-AAC codec is selected,
and its MON button enabled, the audition point is post the HD-AAC encoder-decoder.
You will notice that the DIFF signal in the FFT display will drop below -144dB. (HD-AAC
is lossless to 24 bits, so the DIFF signal has an amplitude smaller than 24 bits down. If the
input signal to the codec is quantised to 24 bits, either by dither and truncation, or because it
is unprocessed data from a 24-bit input file, the diff signal will drop below -180dB).
While encoding/auditioning an HD-AAC signal, attention should be paid to the lossy core.
We recommend selecting the appropriate core codec in an adjacent codec window, which
will allow correct auditioning of the lossy codec in the HD-AAC channel, and will also allow
correct overload monitoring and mitigation.
The HD-AAC lossy core takes the parameters:
Bitrate Selectable from 96kbps to 192kbps
Mode CBR
Quality Medium
However, remember that if the BITSTREAM LEVELS TRIM function is used to mitigate
the core codec overload, and if that same trim value is applied to the HD-AAC encoder input,
then both the lossless and the lossy data streams will be trimmed.
Also note that, under normal circumstances, if the lossless codec’s Bitstream Level Trim is
non-zero to avoid clipping in the lossy chain for an offline encode that uses the online trim
values, then the resulting decoded output file will not be lossless because the level has
changed.