Custom control of frequencies
It is planned to offer the possibility to load custom FIR filters for all the codecs and all the sampling rates.
This is useful for personalized audio output and hearing corrections. The filters will be generated from XML text files containing the relative sensitivity of each ear at different frequencies (as the audiogram data).
The FIR filters will be dynamically generated and loaded at startup and will be applied in the Fourier domain (fast convolutions).
The equalize.exe utility
On Windows, an utility called equalize.exe will be provided. This utility will allow to test the functions of the frequency equalization.
From a WAVE file, it will encode and then decode with the selected codec. During the decompression, it will apply the selected settings for the equalization. The play.exe utility or an other WAVE file player will be used to read the output file.
The equalize.exe utility will allow to know the parameters that correspond to your own needs. Run the utility without parameter to have the list of all the available parameters.
The equalize.exe utility will support the uncompressed PCM codecs (pcm8, pcm16, pcm32 and pcm48, for the 8, 16, 32 and 48 kHz sampling rates).
For the treatments, the FFT and inverse FFT transformations will be performed on the decoder side.