使用 DirectSound 录制麦克风音频
使用 DirectSound 录制麦克风音频
本文所有代码均可在以下仓库找到
https://gitcode.net/PeaZomboss/learnaudios
目录是demo/dscapture
之前那篇文章简单介绍了DirectSound，并用其实现了对WAV格式文件的播放操作，本文将继续聚焦于DirectSound，但目标变成了用其实现对麦克风音频的录制，并将其保存为WAV格式的文件。
DirectSound录制的方法和播放的方法其实差不多，都是使用循环+多缓冲的方法，在实际写代码的过程中没有什么很大的不同，也无需过多解释，所以本文主要就是展示一些关键代码。
关于IDirectSoundCapture等接口的具体定义还是建议直接看文档就行了。
https://docs.microsoft.com/en-us/previous-versions/windows/desktop/ee416960(v=vs.85)
接口定义
接口和播放器的非常相似，仅有部分小改动
// 参数1：缓冲区指针
// 参数2：缓冲区大小（单位字节）
// 参数3：用户自定义指针
typedef void (*CopyBufCallback)(void *, int, void *);
DWord WINAPI copy_thread(void *parameter);
class Recorder
{
private:
IDirectSoundCapture *dsc;
IDirectSoundCaptureBuffer *dscb;
CopyBufCallback copybuf_func;
void *copybuf_ctx;
WAVEFORMATEX fmtex;
DWord block_size;
DWord buf_size;
HANDLE events[3];
HANDLE h_copy_thread; // copy_thread线程句柄
bool recording; // 录制中（包括暂停）
bool suspended; // 是否挂起，用于暂停
void copy_buf(void *ptr, int len); // 方便调用
public:
friend DWord WINAPI copy_thread(void *parameter);
Recorder();
Recorder(GUID *device);
~Recorder();
void set_block_size(DWord bs);
void set_fmt(const WAVEFORMATEX &fmtex);
void set_copy_buf_callback(CopyBufCallback copy, void *ctx);
void start();
void stop();
void pause();
void resume();
};
具体实现
对于录制功能的实现，使用简单的双缓冲即可，目前暂未发现一些问题。
线程实现如下：
DWord WINAPI copy_thread(void *parameter)
{
Recorder *recorder = (Recorder *)parameter;
void *ptr;
DWord len;
while (true) {
DWORD res = WaitForMultipleObjects(3, &recorder->events[0], FALSE, INFINITE);
if (res == 0) { // 录制第一段缓冲区时保存第二段
recorder->dscb->Lock(recorder->buf_size, recorder->buf_size, &ptr, &len, NULL, NULL, 0);
recorder->copy_buf(ptr, len);
recorder->dscb->Unlock(ptr, len, NULL, 0);
}
else if (res == 1) { // 同理保存第一段
recorder->dscb->Lock(0, recorder->buf_size, &ptr, &len, NULL, NULL, 0);
recorder->copy_buf(ptr, len);
recorder->dscb->Unlock(ptr, len, NULL, 0);
}
else { // 保存剩下部分
DWord pos;
recorder->dscb->Stop();
recorder->dscb->GetCurrentPosition(&pos, NULL);
// 根据当前录制位置确定是在第一段还是第二段缓冲区
if (pos > recorder->buf_size)
recorder->dscb->Lock(recorder->buf_size, pos - recorder->buf_size, &ptr, &len, NULL, NULL, 0);
else
recorder->dscb->Lock(0, pos, &ptr, &len, NULL, NULL, 0);
recorder->copy_buf(ptr, len);
recorder->dscb->Unlock(ptr, len, NULL, 0);
break;
}
}
printf("Recording thread end.\n");
return 0;
}
然后是start()的实现：
void Recorder::start()
{
if (dscb || recording) return;
buf_size = block_size * fmtex.nBlockAlign;
DSCBUFFERDESC dscbd;
memset(&dscbd, 0, sizeof(DSCBUFFERDESC));
dscbd.dwSize = sizeof(DSCBUFFERDESC);
dscbd.dwBufferBytes = buf_size * 2; // 使用双缓冲
dscbd.lpwfxFormat = &fmtex;
HRESULT hr = dsc->CreateCaptureBuffer(&dscbd, &dscb, NULL);
if (FAILED(hr)) {
printf("Can not create capture buffer\n");
return;
}
void *ptr;
DWord len;
dscb->Lock(0, 0, &ptr, &len, NULL, NULL, DSCBLOCK_ENTIREBUFFER);
memset(ptr, 0, len); // 清空整个缓冲区
dscb->Unlock(ptr, len, NULL, 0);
IDirectSoundNotify *dsn;
hr = dscb->QueryInterface(_iid_IDirectSoundNotify, (void **)&dsn);
if (FAILED(hr)) {
printf("Can not query direct sound notify\n");
return;
}
DSBPOSITIONNOTIFY dsbpn[2];
dsbpn[0].dwOffset = 0;
dsbpn[0].hEventNotify = events[0];
dsbpn[1].dwOffset = buf_size;
dsbpn[1].hEventNotify = events[1];
dsn->SetNotificationPositions(2, &dsbpn[0]); // 设置通知位置
dsn->Release();
recording = true;
dscb->Start(DSCBSTART_LOOPING);
printf("Recording ...\n");
DWord copy_thread_id = 0;
h_copy_thread = CreateThread(NULL, 0, copy_thread, this, 0, ©_thread_id);
printf("Record thread handle: %d, thread id: %d\n", h_copy_thread, copy_thread_id);
suspended = false;
}
stop()，pause()，resume()的实现：
void Recorder::stop()
{
if (recording) {
printf("Stopping...\n");
SetEvent(events[2]);
WaitForSingleObject(h_copy_thread, 1000); // 等待线程结束
dscb->Release();
dscb = NULL;
recording = false;
printf("Done...\n");
}
}
void Recorder::pause()
{
if (recording && !suspended) {
dscb->Stop();
suspended = true;
printf("pause\n");
}
}
void Recorder::resume()
{
if (recording && suspended) {
dscb->Start(DSCBSTART_LOOPING);
suspended = false;
printf("resume\n");
}
}
主程序
为了方便将数据写入文件，使用全局变量如下：
FILE *fp;
DWord total_len = 0; // 保存实际写入的数据长度（单位字节）
然后是保存缓冲区数据的方法：
void copy_buf(void *buf, int len, void *ctx)
{
int wt_size = fwrite(buf, 1, len, fp);
total_len += wt_size; // 累加写入的长度
}
然后就是主函数：
int main()
{
char fn[256];
SYSTEMTIME st;
GetLocalTime(&st); // 获取当前时间
// 根据时间生成文件名
sprintf(fn, "%d-%d-%d_%02d%02d%02d.wav", st.wYear, st.wMonth, st.wDay, st.wHour, st.wMinute, st.wSecond);
fp = fopen(fn, "wb");
RIFFHeader rh;
strncpy(rh.id.chr, "RIFF", 4);
rh.size = 0; // 暂时填零
strncpy(rh.type.chr, "WAVE", 4);
fwrite(&rh, sizeof(RIFFHeader), 1, fp); // 写入RIFF头
RIFFChunkHeader rch;
strncpy(rch.id.chr, "fmt ", 4);
rch.size = sizeof(WAVEFORMATEX) - sizeof(WORD); // 不要多余的cbSize字段
fwrite(&rch, sizeof(RIFFChunkHeader), 1, fp); // 写入fmt头
WAVEFORMATEX fmtex;
fmtex.wFormatTag = 1;
fmtex.nChannels = 2;
fmtex.nSamplesPerSec = 16000;
fmtex.wBitsPerSample = 16;
fmtex.nBlockAlign = 4;
fmtex.nAvgBytesPerSec = 16000 * 4;
fmtex.cbSize = 0;
fwrite(&fmtex, sizeof(WAVEFORMATEX) - sizeof(WORD), 1, fp); // 写入fmt内容
strncpy(rch.id.chr, "data", 4);
rch.size = 0; // 同理
fwrite(&rch, sizeof(RIFFChunkHeader), 1, fp); // 写入data头
Recorder recorder;
recorder.set_fmt(fmtex);
recorder.set_copy_buf_callback(copy_buf, NULL);
recorder.start();
int command = 0;
printf("Input 'q' to quit, 'p' to pause, 'r' to resume\n");
do {
command = getchar();
if (command == 'p')
recorder.pause();
else if (command == 'r')
recorder.resume();
} while (command != 'q');
recorder.stop();
printf("Total got %d (bytes) data\n", total_len);
// 回到文件头写入实际的大小信息
DWord riff_size = total_len + 44 - 8; // 头部共占用44字节内容
fseek(fp, 4, SEEK_SET); // 此处使用硬编码，实际使用不推荐
fwrite(&riff_size, 4, 1, fp); // 重新写入实际的大小
fseek(fp, 40, SEEK_SET); // 同上
fwrite(&total_len, 4, 1, fp);
fclose(fp);
printf("Saved to file \"%s\", size: %d\n", fn, riff_size + 8);
}
