我正在處理一個wav文件的幅度和縮放一些十進制的因素。我試圖圍繞如何以有效的內存方式讀取和重寫文件,同時試圖解決語言的細微差別(我是C的新手)。該文件可以是8位或16位格式。我認爲這樣做的方法是首先將header data讀入一些預定義的結構中,然後在循環中處理實際數據,在該循環中我將讀取一塊數據到緩衝區中,執行所需的任何操作,以及然後將其寫入輸出。處理音頻wav文件與C
#include <stdio.h>
#include <stdlib.h>
typedef struct header
{
char chunk_id[4];
int chunk_size;
char format[4];
char subchunk1_id[4];
int subchunk1_size;
short int audio_format;
short int num_channels;
int sample_rate;
int byte_rate;
short int block_align;
short int bits_per_sample;
short int extra_param_size;
char subchunk2_id[4];
int subchunk2_size;
} header;
typedef struct header* header_p;
void scale_wav_file(char * input, float factor, int is_8bit)
{
FILE * infile = fopen(input, "rb");
FILE * outfile = fopen("outfile.wav", "wb");
int BUFSIZE = 4000, i, MAX_8BIT_AMP = 255, MAX_16BIT_AMP = 32678;
// used for processing 8-bit file
unsigned char inbuff8[BUFSIZE], outbuff8[BUFSIZE];
// used for processing 16-bit file
short int inbuff16[BUFSIZE], outbuff16[BUFSIZE];
// header_p points to a header struct that contains the file's metadata fields
header_p meta = (header_p)malloc(sizeof(header));
if (infile)
{
// read and write header data
fread(meta, 1, sizeof(header), infile);
fwrite(meta, 1, sizeof(meta), outfile);
while (!feof(infile))
{
if (is_8bit)
{
fread(inbuff8, 1, BUFSIZE, infile);
} else {
fread(inbuff16, 1, BUFSIZE, infile);
}
// scale amplitude for 8/16 bits
for (i=0; i < BUFSIZE; ++i)
{
if (is_8bit)
{
outbuff8[i] = factor * inbuff8[i];
if ((int)outbuff8[i] > MAX_8BIT_AMP)
{
outbuff8[i] = MAX_8BIT_AMP;
}
} else {
outbuff16[i] = factor * inbuff16[i];
if ((int)outbuff16[i] > MAX_16BIT_AMP)
{
outbuff16[i] = MAX_16BIT_AMP;
} else if ((int)outbuff16[i] < -MAX_16BIT_AMP) {
outbuff16[i] = -MAX_16BIT_AMP;
}
}
}
// write to output file for 8/16 bit
if (is_8bit)
{
fwrite(outbuff8, 1, BUFSIZE, outfile);
} else {
fwrite(outbuff16, 1, BUFSIZE, outfile);
}
}
}
// cleanup
if (infile) { fclose(infile); }
if (outfile) { fclose(outfile); }
if (meta) { free(meta); }
}
int main (int argc, char const *argv[])
{
char infile[] = "file.wav";
float factor = 0.5;
scale_wav_file(infile, factor, 0);
return 0;
}
我在最後得到不同的文件大小(以1K左右,對於一個40MB的文件),我懷疑這是由於這樣的事實,我正在寫一整個緩衝區輸出,即使該文件在填充整個緩衝區大小之前可能已經終止。另外,輸出文件會搞砸 - 不會播放或打開 - 所以我可能會做錯整個事情。任何關於我搞砸的提示都會很棒。謝謝!
當你說的輸入和輸出文件具有不同的大小,是輸出文件大於還是小於輸入? – bta 2010-03-16 19:51:21
輸出較大 – sa125 2010-03-16 20:07:35