Merge pull request 'Add linear fade-out to IRs with --fade-ms option (default 5ms); update README and CLI' (#1) from feature/fade-out into main

Reviewed-on: #1

README.md

@@ -7,6 +7,7 @@ A CLI tool for processing WAV files to generate impulse responses (IR) from swee
 - **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
+- **Automatic fade-out:** Linear fade-out at the end of the IR to avoid clicks (default 5 ms, configurable with --fade-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
@@ -57,6 +58,16 @@ Trim or zero-pad the output IR to a specific length (in milliseconds):
 
 This will ensure the output IR is exactly 100 ms long (trimming or zero-padding as needed).
 
+### Fade-Out to Avoid Clicks
+
+By default, a 5 ms linear fade-out is applied to the end of the IR to avoid clicks. You can change the fade duration:
+
+```sh
+./valhallir-deconvolver --sweep sweep.wav --recorded recorded.wav --output ir.wav --fade-ms 10
+```
+
+This applies a 10 ms fade-out at the end of the IR.
+
 ### Different Output Formats
 
 Generate IRs in different sample rates and bit depths:
@@ -116,6 +127,7 @@ Generate IRs in different sample rates and bit depths:
 | `--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 |
+| `--fade-ms` | Fade-out duration in milliseconds at end of IR (default 5) | 5 | No |
 
 ## File Requirements
 
@@ -143,6 +155,10 @@ Generate IRs in different sample rates and bit depths:
 - 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
 
+### Fade-Out
+- By default, a 5 ms linear fade-out is applied to the end of the IR (and MPT IR) to avoid clicks
+- You can change the fade duration with `--fade-ms`
+
 ### Deconvolution Process
 1. **FFT-based deconvolution** of recorded signal by sweep signal
 2. **Regularization** to prevent division by zero

go.mod

@@ -1,6 +1,6 @@
 module valhallir-deconvolver
 
-go 1.24.1
+go 1.24.5
 
 require (
 	dagger.io/dagger v0.18.12

main.go

@@ -60,6 +60,11 @@ func main() {
 				Name:  "length-ms",
 				Usage: "Optional: Output IR length in milliseconds (will trim or zero-pad as needed)",
 			},
+			&cli.Float64Flag{
+				Name:  "fade-ms",
+				Usage: "Fade-out duration in milliseconds to apply at the end of the IR (default 5)",
+				Value: 5.0,
+			},
 		},
 		Action: func(c *cli.Context) error {
 			// Read sweep WAV file
@@ -135,6 +140,14 @@ func main() {
 				ir = convolve.TrimOrPad(ir, targetSamples)
 			}
 
+			// Apply fade-out
+			fadeMs := c.Float64("fade-ms")
+			fadeSamples := int(float64(targetSampleRate) * fadeMs / 1000.0)
+			if fadeSamples > 0 {
+				log.Printf("Applying linear fade-out: %d samples (%.2f ms)...", fadeSamples, fadeMs)
+				ir = convolve.FadeOutLinear(ir, fadeSamples)
+			}
+
 			// Write regular IR
 			log.Printf("Writing IR to: %s (%dHz, %d-bit WAV)", c.String("output"), sampleRate, bitDepth)
 			if err := wav.WriteWAVFileWithOptions(c.String("output"), ir, sampleRate, bitDepth); err != nil {
@@ -165,6 +178,12 @@ func main() {
 					mptIR = convolve.TrimOrPad(mptIR, targetSamples)
 				}
 
+				// Apply fade-out to MPT IR
+				if fadeSamples > 0 {
+					log.Printf("Applying linear fade-out to MPT IR: %d samples (%.2f ms)...", fadeSamples, fadeMs)
+					mptIR = convolve.FadeOutLinear(mptIR, fadeSamples)
+				}
+
 				// Generate MPT output filename
 				outputPath := c.String("output")
 				if len(outputPath) > 4 && outputPath[len(outputPath)-4:] == ".wav" {

pkg/convolve/convolve.go

@@ -322,3 +322,22 @@ func Resample(data []float64, fromSampleRate, toSampleRate int) []float64 {
 
 	return result
 }
+
+// FadeOutLinear applies a linear fade-out to the last fadeSamples of the data.
+// fadeSamples is the number of samples over which to fade to zero.
+func FadeOutLinear(data []float64, fadeSamples int) []float64 {
+	if fadeSamples <= 0 || len(data) == 0 {
+		return data
+	}
+	if fadeSamples > len(data) {
+		fadeSamples = len(data)
+	}
+	out := make([]float64, len(data))
+	copy(out, data)
+	start := len(data) - fadeSamples
+	for i := start; i < len(data); i++ {
+		fade := float64(len(data)-i) / float64(fadeSamples)
+		out[i] *= fade
+	}
+	return out
+}