[英]Writing to WAV file C++
我有一個關於數字信號處理課程的WAV
文件和FIR
濾波器的作業。
我的程序必須讀取一個WAV
文件,對數據應用過濾器並將輸出數據再次寫入另一個WAV
文件。
我已完成閱讀和應用過濾器,但無法編寫WAV
文件。 該程序在編譯時沒有給出任何錯誤,但WAV
文件不播放。
如果我將"temp"
寫入WAV
,它會正常運行。 但如果我寫"data"
,它不會。
如何正確編寫 WAV 文件?
#define _CRT_SECURE_NO_WARNINGS
#define PI 3.14f
#define WAV_HEADER_LENGTH 44
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <iostream>
#include <fstream>
char* read_wav(const char* filename, short*, short*, int*);
void write_wav(const char* filename, const char*, int);
using namespace std;
int main()
{
short nchannel, ssample;
int csample;
//Reading WAV file and returning the data.
char* temp = read_wav("sum.wav", &nchannel, &ssample, &csample);
short* data = (short*)&temp[WAV_HEADER_LENGTH];
cout << "How many coefficients are there in filter ?" << endl;
int N;
cin >> N ;
float filter[N];
cout << "Type coefficients in filter." << endl;
for(int i=0; i<N;i++){
cin >> filter[i];
}
short* output = (short*)&temp[WAV_HEADER_LENGTH];
for(int i=0; i < csample; i++){
double sum = 0;
for(int j=0; j < N; j++){
if((i - j) >= 0)
sum += filter[j] * data[i-j];
}
output[i] = (short) sum;
}
write_wav("test.wav", out, csample * ssample + WAV_HEADER_LENGTH);
}
char* read_wav(const char* filename, short* nchannel, short* ssample, int* csample) {
//Reading the file.
FILE* fp = fopen(filename, "rb");
if (!fp) {
fprintf(stderr, "Couldn't open the file \"%s\"\n", filename);
exit(0);
}
fseek(fp, 0, SEEK_END);
int file_size = ftell(fp);
fseek(fp, 0, SEEK_SET);
printf("The file \"%s\" has %d bytes\n\n", filename, file_size);
char* buffer = (char*)malloc(sizeof(char) * file_size);
fread(buffer, file_size, 1, fp);
// Dump the buffer info.
*nchannel = *(short*)&buffer[22];
*ssample = *(short*)&buffer[34] / 8;
*csample = *(int*)&buffer[40] / *ssample;
printf("ChunkSize :\t %u\n", *(int*)&buffer[4]);
printf("Format :\t %u\n", *(short*)&buffer[20]);
printf("NumChannels :\t %u\n", *(short*)&buffer[22]);
printf("SampleRate :\t %u\n", *(int*)&buffer[24]); // number of samples per second
printf("ByteRate :\t %u\n", *(int*)&buffer[28]); // number of bytes per second
printf("BitsPerSample :\t %u\n", *(short*)&buffer[34]);
printf("Subchunk2ID :\t \"%c%c%c%c\"\n", buffer[36], buffer[37], buffer[38], buffer[39]); // marks beginning of the data section
printf("Subchunk2Size :\t %u\n", *(int*)&buffer[40]); // size of data (byte)
printf("Duration :\t %fs\n\n", (float)(*(int*)&buffer[40]) / *(int*)&buffer[28]);
fclose(fp);
return buffer;
}
void write_wav(const char* filename, const char* data, int len) {
FILE* fp = fopen(filename, "wb");
if (!fp) {
fprintf(stderr, "Couldn't open the file \"%s\"\n", filename);
exit(0);
}
fwrite(data, len, 1, fp);
fclose(fp);
}
這對我有用:
int main()
{
short nchannel, ssample;
int csample;
// Reading WAV file and returning the data.
char* temp = read_wav("sum.wav", &nchannel, &ssample, &csample);
short* data = (short*)&temp[WAV_HEADER_LENGTH];
// cout << "How many coefficients are there in filter ?" << endl;
const int N = 2;
// cin >> N;
float filter[N] = {0.5, 0.75};
// cout << "Type coefficients in filter." << endl;
// for (int i = 0; i < N; i++)
// {
// cin >> filter[i];
// }
short* output = (short*)&temp[WAV_HEADER_LENGTH];
for (int i = 0; i < csample; i++)
{
double sum = 0;
for (int j = 0; j < N; j++)
{
if ((i - j) >= 0) sum += filter[j] * data[i - j];
}
output[i] = (short)sum;
}
write_wav("test.wav", (char*)temp, csample * ssample + WAV_HEADER_LENGTH);
}
我的變化:
temp
,而不是你的out
不編譯,作為write_wav
的參數。如果代碼是可移植的,您需要檢查字節序並采取相應措施。
我希望輸入和輸出文件的長度相同,但事實並非如此。 請自行檢查為什么不是這種情況。 例子:
-rw-r--r-- 1 zkoza zkoza 787306 06-23 14:09 sum.wav
-rw-r--r-- 1 zkoza zkoza 787176 06-23 14:16 test.wav
輸出文件中似乎缺少 130 個字節。
在編譯時N
未知的float filter[N]
是 C++ 擴展:請在最終代碼中使用std::vector
。
下次請提供任何輸入文件的鏈接。 對於我的測試,我使用了https://freewavesamples.com/alesis-fusion-clean-guitar-c3 ,但是所有這些小東西,比如查找輸入文件(WAV 格式有多種風格,我可能錯過了正確的一種) ,猜測過濾器參數等需要時間和精力。
您的條件if ((i - j) >= 0)
可以用更容易理解的方式編寫; 最好通過更改內部循環“標題”。
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