Fast FFT-based deconvolution for accurate IR extraction
Automatic input conversion: Accepts any WAV sample rate, bit depth, or channel count
Optional output IR length: Specify output IR length in milliseconds with --length-ms
96kHz 24-bit WAV file support for high-quality audio processing
Multiple output formats with configurable sample rates and bit depths
Minimum Phase Transform (MPT) option for reduced latency IRs
Automatic silence trimming and normalization
Modular design with separate packages for WAV I/O and convolution
Robust error handling and validation

Installation

# Clone the repository
git clone <repository-url>
cd valhallir-convoluter

# Build the application
go build -o valhallir-convoluter

Usage

Basic IR Generation

Generate a standard impulse response from sweep and recorded files (any WAV format):

./valhallir-convoluter --sweep sweep.wav --recorded recorded.wav --output ir.wav

With Minimum Phase Transform

Generate both regular and minimum phase IRs:

./valhallir-convoluter --sweep sweep.wav --recorded recorded.wav --output ir.wav --mpt

This creates:

ir.wav - Standard impulse response
ir_mpt.wav - Minimum phase transform version

Limit Output IR Length

Trim or zero-pad the output IR to a specific length (in milliseconds):

./valhallir-convoluter --sweep sweep.wav --recorded recorded.wav --output ir.wav --length-ms 100

This will ensure the output IR is exactly 100 ms long (trimming or zero-padding as needed).

Different Output Formats

Generate IRs in different sample rates and bit depths:

# 44kHz 16-bit (CD quality)
./valhallir-convoluter \
  --sweep sweep.wav \
  --recorded recorded.wav \
  --output ir_cd.wav \
  --sample-rate 44100 \
  --bit-depth 16

# 48kHz 32-bit (studio quality)
./valhallir-convoluter \
  --sweep sweep.wav \
  --recorded recorded.wav \
  --output ir_studio.wav \
  --sample-rate 48000 \
  --bit-depth 32 \
  --mpt

# 96kHz 24-bit (high resolution)
./valhallir-convoluter \
  --sweep sweep.wav \
  --recorded recorded.wav \
  --output ir_hires.wav \
  --sample-rate 96000 \
  --bit-depth 24

Advanced Options

./valhallir-convoluter \
  --sweep sweep.wav \
  --recorded recorded.wav \
  --output ir.wav \
  --mpt \
  --sample-rate 48000 \
  --bit-depth 24 \
  --normalize 0.95 \
  --trim-threshold 0.001 \
  --length-ms 50

Command Line Options

Flag	Description	Default	Required
`--sweep`	Path to sweep WAV file (any format)	-	Yes
`--recorded`	Path to recorded WAV file (any format)	-	Yes
`--output`	Path to output IR WAV file	-	Yes
`--mpt`	Generate minimum phase transform IR	false	No
`--sample-rate`	Output sample rate (44, 48, 88, 96 kHz)	96000	No
`--bit-depth`	Output bit depth (16, 24, 32 bit)	24	No
`--normalize`	Normalize output to peak value (0.0-1.0)	0.95	No
`--trim-threshold`	Silence threshold for trimming (0.0-1.0)	0.001	No
`--length-ms`	Output IR length in milliseconds (trim or zero-pad)	-	No

File Requirements

Input Files

Format: Any uncompressed WAV file
Sample Rate: Any (will be automatically resampled to 96kHz for processing)
Bit Depth: Any (16, 24, 32-bit supported; will be converted to float64 internally)
Channels: Any (mono, stereo, or multi-channel; will be converted to mono by averaging channels)

Output Files

Format: WAV files
Sample Rate: 44kHz, 48kHz, 88kHz, or 96kHz (set by --sample-rate)
Bit Depth: 16-bit, 24-bit, or 32-bit (set by --bit-depth)
Channels: Mono (1 channel)

Technical Details

Input Conversion

All input files are automatically converted to mono, 96kHz, float64 for processing
Stereo or multi-channel files are averaged to mono
Sample rates are resampled to 96kHz using linear interpolation
Bit depths are normalized to float64

Output IR Length

If --length-ms is set, the output IR (and MPT IR) will be trimmed or zero-padded to the specified length in milliseconds
If not set, the full IR is used

Deconvolution Process

FFT-based deconvolution of recorded signal by sweep signal
Regularization to prevent division by zero
Silence trimming to remove leading/trailing silence
Normalization to prevent clipping

Minimum Phase Transform

Uses real cepstrum method for accurate minimum phase conversion
Reduces latency by minimizing pre-ringing
Maintains frequency response while optimizing phase characteristics
Suitable for real-time applications like guitar amp modeling

Output Format Options

Sample Rates: 44.1kHz (CD), 48kHz (studio), 88.2kHz, 96kHz (high-res)
Bit Depths: 16-bit (CD), 24-bit (studio), 32-bit (high-res)
File Sizes: 16-bit ≈ 50% smaller, 32-bit ≈ 33% larger than 24-bit

Dependencies

urfave/cli - CLI framework
go-audio/wav - WAV file I/O
go-dsp/fft - FFT implementation
gonum - Numerical computing

Examples

Guitar Cabinet IR (CD Quality)

# Generate IR from guitar cab sweep and recording (any WAV format), 50ms length
./valhallir-convoluter \
  --sweep guitar_cab_sweep.wav \
  --recorded guitar_cab_recorded.wav \
  --output cab_ir_cd.wav \
  --sample-rate 44100 \
  --bit-depth 16 \
  --length-ms 50 \
  --mpt

Room Acoustics IR (Studio Quality)

# Generate room impulse response
./valhallir-convoluter \
  --sweep room_sweep.wav \
  --recorded room_recorded.wav \
  --output room_ir_studio.wav \
  --sample-rate 48000 \
  --bit-depth 24

High-Resolution IR (Mastering)

# Generate high-resolution IR for mastering
./valhallir-convoluter \
  --sweep mastering_sweep.wav \
  --recorded mastering_recorded.wav \
  --output mastering_ir.wav \
  --sample-rate 96000 \
  --bit-depth 32 \
  --length-ms 100 \
  --mpt

Troubleshooting

Common Issues

"File is not a valid WAV file" error

Check that files are uncompressed WAV format
Avoid MP3, FLAC, or other compressed formats

"Invalid sample rate" error (output)

Use only supported output sample rates: 44100, 48000, 88200, 96000
Check the --sample-rate flag value

"Invalid bit depth" error (output)

Use only supported output bit depths: 16, 24, 32
Check the --bit-depth flag value

Performance

Processing time depends on file length
FFT-based deconvolution is much faster than time-domain methods
Large files (>1GB) may take several minutes
Higher bit depths require more memory but don't significantly affect processing time

License

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Contributing

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