File Formats
HouseCurve can read/write any files that are visible from the Files app. This includes local storage on the iPhone/iPad, but also iCloud, Samba, DropBox, OneDrive, etc.
To use a file from a website, download it to the local iPhone/iPad storage and then select from within HouseCurve.
To transfer files, you can just use HouseCurve to save to the desired location. Or you can save to the local storage and then share with text message, email, AirDrop, etc.
Curves
A space, tab or comma delimited text file with a frequency (Hz) followed by a gain (dB) on each line. A third phase value may be included but is ignored. Lines starting with non-numeric characters are ignored. Frequencies must be listed in increasing order. HouseCurve will interpolate a curve from 20-20000 Hz using the values provided. The file extension may be txt or frd.
Measurements
Saved measurements can be exported as impulse responses for use in other tools. The file format is a monural WAV. Samples are 32-bit floating point. The impulse response peak will appear at 250 ms, when no delays are present. The file is padded out to 1 second in length.
Filters
HouseCurve supports the same filter formats as REW. These are quasi-standard, but may not work with all equalizers. When trying this out for the first time, turn the volume down as a precaution. For support, questions and suggestions, please reach out.
Biquad Coefficients
A text file containing biquad transfer function coefficients b0, b1, b2, a1, a2 where a0 is normalized to 1.0, and the signs of a1, a2 are flipped. This format depends on the selected sample rate. The file extension is txt.
This format is compatible with miniDSP hardware. For other equalizers (ex: CamillaDSP), the signs of a1 and a2 need to be flipped.
Parametric EQ Settings
A text file containing human-readable equalizer settings (frequency, gain, Q). See format for more information. The file extension is txt.
This format is meant for systems with a parametric equalizer, such as Volumio, HifiBerry, Equalizer APO, etc.
Impulse reponses
FIR and PEQ filters can be exported as impulse responses for use in audio systems with a convolution engine (aka “convolver”). The system must support at least 500 ms long FIR filters (ex: 24000 samples or “taps” at 48000 KHz). Systems such as Roon, moOde, CamillaDSP, Volumio have this capability. Beware that some systems support only short FIR filters, such as the miniDSP-2x4HD.
The file format is a monural WAV. Samples are 32-bit floating point. The length of the file is 500 ms. With PEQ filters, the impulse peak is at first sample (zero delay). FIR filters have the impulse peak at 250 ms. This is to accommodate some pre-ringing in the filter.
Test signal
A stereo WAV formatted audio file containing the “chirp” and “sweep” sounds. Samples are 32-bit floating point. The sample rate is 44.1 KHz. See externally played sweeps for more information.