Spectrice is a spectral freezing tool, mostly intended for freezing the spectral character of a sample in preparation for looping.
No libraries are required, only a compiler. The Makefile might need adjusting, however, if your target platform is not Windows, or you need to adjust the architectural features (eg. disable AVX, FMA, etc.).
After adjusting the Makefile as needed, run make all to build the tool.
Spectrice uses WAV files for input/output, in 8-bit PCM, 16-bit PCM, 24-bit PCM, or 32-bit IEEE floating-point formats.
The processing library itself works on 32-bit floating-point blocks of data, however, and can be used standalone.
spectrice Input.wav Output.wav [Options]
Options:
| Option | Effect |
|---|---|
-blocksize:X |
Set transform block size. (Default: 8192, Minimum: 16, Maximum: 65536) |
-nhops:X |
Set number of hops per transform block. (Default: 8. Minimum depends on window type) |
-window:X |
Set analysis+synthesis window function. |
Can be any of: sine, hann, hamming, blackman, nuttall. (Default: Nuttall) |
|
-freezexfade:X |
Set number of samples to crossfade/blend prior to the freeze point. (Default: 0) |
-freezepoint:X |
Set the point at which the freezing effect is at full strength. (Default: 0, but this is useless) |
-freezefactor:X |
Set strength of freezing effect. (Default: 1.0) |
-nofreezeamp |
Do not freeze amplitude (useless by itself; combine with freezephase. |
-freezephase |
Freeze the phase step. |
-format:default |
Set the output file format (PCM8, PCM16, PCM24, FLOAT32, or default). |
- Due to limitations in STFT re-synthesis, loops might 'pop' at the boundaries. Increasing the number of hops, or moving the loop to a zero-crossing after freezing might help.
- Using small or overly-large transform sizes might result in strange freezing characteristics. This may be useful for effects, but might not be desired.
- A number of different windows are provided, as they all provide different pros and cons; it may be necessary to experiment with the window type and number of hops.
- Phase step freezing isn't perfect, as this can't capture small deviations caused by off-center frequencies during DFT analysis. In practice, this can result in an "infinitely evolving" waveform.
- Decompose signal using STFT (using a centered DFT algorithm based on DCT-IV and DST-IV).
- Transform Re/Im pairs into Amplitude/Phase.
- Apply freezing:
- Interpolate amplitude from the last segment based on the freezing ratio and crossfade time (without
-nofreezeamp). - Interpolate phase step from the last segment based on the freezing ratio and crossfade time (with
freezephase).
- Interpolate amplitude from the last segment based on the freezing ratio and crossfade time (without
- Transform back to Re/Im pairs.
- Apply inverse STFT.
Add WAV file support.Added 2022/12/14- Add support for freezing only a specified loop section, with correct handling of wrapping behaviour.
- Ruben Nunez - Initial work - Aikku93
Spectrice is released under the GPLv3 license. See the LICENSE file for full terms.
- Huge thanks to
musicalmanfor testing and providing ideas to implement.