编辑：我更新了下面的代码以类似于我取得的进展。我正在尝试自己编写.wav标题。截至目前，该代码无法正常工作，音频未正确写入文件。该代码尚不包含任何将其转换为文件的尝试.flac。
我正在使用 Raspberry Pi ( Debian Linux ) 通过ALSA 库录制音频。录音工作正常，但我需要将输入音频编码到 FLAC 编解码器中。
这就是我迷路的地方。我花了相当多的时间试图弄清楚如何将这些原始数据转换为FLAC，但我不断提出如何将.wav文件转换为.flac文件的示例。
这是我使用 ALSA 录制音频的当前（更新）代码（可能有点粗糙，我仍在使用 C++）：
// Use the newer ALSA API
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Riff
{
char chunkId[4]; // "RIFF" (assuming char is 8 bits)
int chunkSize; // (assuming int is 32 bits)
char format[4]; // "WAVE"
};
struct Format
{
char chunkId[4]; // "fmt "
int chunkSize;
short format; // assuming short is 16 bits
short numChannels;
int sampleRate;
int byteRate;
short align;
short bitsPerSample;
};
struct Data
{
char chunkId[4]; // "data"
int chunkSize; // length of data
char* data;
};
struct Wave // Actual structure of a PCM WAVE file
{
Riff riffHeader;
Format formatHeader;
Data dataHeader;
};
int main(int argc, char *argv[])
{
void saveWaveFile(struct Wave *waveFile);
long loops;
int rc;
int size;
snd_pcm_t *handle;
snd_pcm_hw_params_t *params;
unsigned int sampleRate = 44100;
int dir;
snd_pcm_uframes_t frames;
char *buffer;
char *device = (char*) "plughw:1,0";
//char *device = (char*) "default";
printf("Capture device is %s\n", device);
/* Open PCM device for recording (capture). */
rc = snd_pcm_open(&handle, device, SND_PCM_STREAM_CAPTURE, 0);
if (rc < 0)
{
fprintf(stderr, "Unable to open PCM device: %s\n", snd_strerror(rc));
exit(1);
}
/* Allocate a hardware parameters object. */
snd_pcm_hw_params_alloca(¶ms);
/* Fill it in with default values. */
snd_pcm_hw_params_any(handle, params);
/* Set the desired hardware parameters. */
/* Interleaved mode */
snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
/* Signed 16-bit little-endian format */
snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
/* Two channels (stereo) */
snd_pcm_hw_params_set_channels(handle, params, 2);
/* 44100 bits/second sampling rate (CD quality) */
snd_pcm_hw_params_set_rate_near(handle, params, &sampleRate, &dir);
/* Set period size to 32 frames. */
frames = 32;
snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
/* Write the parameters to the driver */
rc = snd_pcm_hw_params(handle, params);
if (rc < 0)
{
fprintf(stderr, "Unable to set HW parameters: %s\n", snd_strerror(rc));
exit(1);
}
/* Use a buffer large enough to hold one period */
snd_pcm_hw_params_get_period_size(params, &frames, &dir);
size = frames * 4; /* 2 bytes/sample, 2 channels */
buffer = (char *) malloc(size);
/* We want to loop for 5 seconds */
snd_pcm_hw_params_get_period_time(params, &sampleRate, &dir);
loops = 5000000 / sampleRate;
while (loops > 0)
{
loops--;
rc = snd_pcm_readi(handle, buffer, frames);
if (rc == -EPIPE)
{
/* EPIPE means overrun */
fprintf(stderr, "Overrun occurred.\n");
snd_pcm_prepare(handle);
} else if (rc < 0)
{
fprintf(stderr, "Error from read: %s\n", snd_strerror(rc));
} else if (rc != (int)frames)
{
fprintf(stderr, "Short read, read %d frames.\n", rc);
}
if (rc != size) fprintf(stderr, "Short write: wrote %d bytes.\n", rc);
}
Wave wave;
strcpy(wave.riffHeader.chunkId, "RIFF");
wave.riffHeader.chunkSize = 36 + size;
strcpy(wave.riffHeader.format, "WAVE");
strcpy(wave.formatHeader.chunkId, "fmt");
wave.formatHeader.chunkSize = 16;
wave.formatHeader.format = 1; // PCM, other value indicates compression
wave.formatHeader.numChannels = 2; // Stereo
wave.formatHeader.sampleRate = sampleRate;
wave.formatHeader.byteRate = sampleRate * 2 * 2;
wave.formatHeader.align = 2 * 2;
wave.formatHeader.bitsPerSample = 16;
strcpy(wave.dataHeader.chunkId, "data");
wave.dataHeader.chunkSize = size;
wave.dataHeader.data = buffer;
saveWaveFile(&wave);
snd_pcm_drain(handle);
snd_pcm_close(handle);
free(buffer);
return 0;
}
void saveWaveFile(struct Wave *waveFile)
{
FILE *file = fopen("test.wav", "wb");
size_t written;
if (file == NULL)
{
fprintf(stderr, "Cannot open file for writing.\n");
exit(1);
}
written = fwrite(waveFile, sizeof waveFile[0], 1, file);
fclose(file);
if (written < 1);
{
fprintf(stderr, "Writing to file failed, error %d.\n", written);
exit(1);
}
}
我将如何将 PCM 数据转换为 FLAC 并将其保存到磁盘以供以后使用？我已经下载libflac-dev了，只需要一个例子就可以了。
我现在这样做的方式：
./capture > test.raw // or ./capture > test.flac
它应该是这样的（程序为我做了一切）：
./capture