f

Ola.c

@@ -0,0 +1,122 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <math.h>
+#include "wav.h"
+
+#define OVERLAP 0.5
+#define WINDOWLENGTH 4096
+#define SIZECAP 400000
+
+//works better with making files shorter than it does with making them longer
+//use stretchFactor < 1 for shorter files
+//hopefully wsola will be better than ola in this regard
+
+int main(int argc, char *argv[]) {
+	char* filename = argv[1];
+	float stretchFactor = atof(argv[2]);
+
+	struct wav_info info;
+
+	FILE* fp = fopen(filename, "rb");
+	if (!fp) {
+		printf("Error reading file\n");
+		return 1;
+	}
+
+	char* outputName;
+	asprintf(&outputName, "OLA_%s", filename);
+	FILE* op = fopen(outputName, "wb");
+	if (!op) {
+		printf("Error writing file\n");
+		return 1;
+	}
+
+
+	read_wav_info(&info, fp);
+
+	int sizeInBits = info.num_samples * info.num_channels * info.bits_per_sample;
+
+	if (sizeInBits > SIZECAP) {
+		printf("File is too big, must be less than 50 kB\n");
+		return 1;
+	} else if (sizeInBits * stretchFactor > SIZECAP * 4) {
+		printf("stretchFactor is too big\n");
+		return 1;
+	}
+
+	int originalSampleNum = info.num_samples;
+	info.num_samples *= stretchFactor;
+	write_wav_hdr(&info, op);
+
+	//initialize all the variables for the ola algorithm
+	int windowOffset = (1 - OVERLAP) * WINDOWLENGTH;
+	int gammaLength = (int) info.num_samples / windowOffset;
+	int sigmaInterval = windowOffset / stretchFactor;
+	int gamma[gammaLength];
+	int sigma[gammaLength];
+	float window[sigmaInterval];
+
+	//populate gamma and sigma
+	gamma[0] = sigma[0] = 0;
+	for (int i = 1; i < gammaLength; i++) {
+		gamma[i] = gamma[i-1] + windowOffset;
+		sigma[i] = gamma[i] + sigmaInterval;
+	}
+
+	//populate window
+	for (int i = 0; i < sigmaInterval; i++) {
+		window[i] = pow(sin(M_PI * i / (sigmaInterval - 1)), 2);
+	}
+
+	//initialize input and output buffers
+	printf("Initializing input and output buffers\n");
+	printf("Initializing allSamples\n");
+	int_fast32_t allSamples[originalSampleNum][info.num_channels];
+	printf("Initializing outputSamples\n");
+	int_fast32_t outputSamples[info.num_samples][info.num_channels];
+
+	//zero out outputSamples
+	printf("Zeroing out outputSamples");
+	for (int i = 0; i < info.num_samples; i++) {
+		for (int j = 0; j < info.num_channels - 1; j++) {
+			outputSamples[i][j] = 0;
+		}
+	}
+
+	//read all samples into memory
+	printf("Reading all samples into memory\n");
+	for (int i = 0; i < originalSampleNum; i++) {
+		for (int j = 0; j < info.num_channels; j++) {
+			fread(&allSamples[i][j], info.bits_per_sample/8, 1, fp);
+		}
+	}
+
+	//read each frame, window it, and copy it to the output buffer
+	for (int i = 0; i < gammaLength - 2; i++) { //loop through each element of sigma
+		int_fast32_t frame[sigmaInterval][info.num_channels];
+		for (int j = 0; j < sigmaInterval; j++) { //loop through each sample of the frame
+			for (int k = 0; k < info.num_channels; k++) { //loop through each channel of the sample
+				frame[j][k] = allSamples[sigma[i] + j][k] * window[j];
+			}
+		} for (int l = 0; l < sigmaInterval; l++) { //loop through each sample of frame again
+			for (int m = 0; m < info.num_channels; m++) { //to add each sample to output buffer
+				outputSamples[gamma[i] + l][m] += frame[l][m];
+			}
+		}
+
+	}
+
+	//write all samples
+	int_fast32_t sample[info.num_channels];
+	for (int i = 0; i < info.num_samples; i++) {
+		for (int j = 0; j < info.num_channels; j++) {
+			sample[j] = outputSamples[i][j];
+		}
+		write_sample(&info, op, sample);
+	}
+
+	fclose(fp);
+	fclose(op);
+	printf("Successfully stretched file by given factor\n");
+}

WavPlot.py

@@ -18,7 +18,7 @@
         samplerate, data = wavfile.read(wav_fname)
         try:
             length = data.shape[0] / samplerate
-            print(f"num Audio channels = {data.shape[1]}", f"length = {length}s")
+            print(f"number of channels = {data.shape[1]}", f"length = {length}s")
             time = np.linspace(0., length, data.shape[0])
             for i in range(data.shape[1]):
                 plt.plot(time, data[:, i], label=wav_fname.split(".")[0]+"Channel"+str(i))