ffmpeg编码如何实现同时录制声卡和麦克风的声音？

我需要同时录制屏幕，声卡和麦克风的声音。

代码是从http://blog.youkuaiyun.com/dancing_night/article/details/46698853的代码中改的，非常感谢原作者。

代码下面贴出来：

#include "stdafx.h"  
  
#ifdef  __cplusplus  
extern "C"  
{  
#endif  
#include "libavcodec/avcodec.h"  
#include "libavformat/avformat.h"  
#include "libswscale/swscale.h"  
#include "libavdevice/avdevice.h"  
#include "libavutil/audio_fifo.h"  
  
#pragma comment(lib, "avcodec.lib")  
#pragma comment(lib, "avformat.lib")  
#pragma comment(lib, "avutil.lib")  
#pragma comment(lib, "avdevice.lib")  
#pragma comment(lib, "avfilter.lib")  
  
//#pragma comment(lib, "avfilter.lib")  
//#pragma comment(lib, "postproc.lib")  
//#pragma comment(lib, "swresample.lib")  
#pragma comment(lib, "swscale.lib")  
#ifdef __cplusplus  
};  
#endif 

AVFormatContext	*pFormatCtx_Video = NULL, *pFormatCtx_Audio = NULL, *pFormatCtx_Audio_mic = NULL, *pFormatCtx_Out = NULL;
AVCodecContext	*pCodecCtx_Video;
AVCodec			*pCodec_Video;
AVFifoBuffer	*fifo_video = NULL;
AVAudioFifo		*fifo_audio = NULL;
AVAudioFifo		*fifo_audio_mic = NULL;
int VideoIndex, AudioIndex, AudioIndex_mic;

CRITICAL_SECTION AudioSection, AudioSection_mic, VideoSection;

SwsContext *img_convert_ctx;
int frame_size = 0;

uint8_t *picture_buf = NULL, *frame_buf = NULL;

bool bCap = true;
bool bStop = false;
char* m_szPath = "test.mp4";
int m_nFramerate = 15;

DWORD WINAPI startRecordThread(LPVOID lpParam);
DWORD WINAPI ScreenCapThreadProc(LPVOID lpParam);
DWORD WINAPI AudioCapThreadProc(LPVOID lpParam);
DWORD WINAPI AudioMicCapThreadProc(LPVOID lpParam);

int OpenVideoCapture()
{
	AVInputFormat *ifmt = av_find_input_format("gdigrab");
	//这里可以加参数打开，例如可以指定采集帧率
	AVDictionary *options = NULL;
	char szFramerate[4];
	sprintf(szFramerate, "%d", m_nFramerate);
	av_dict_set(&options, "framerate", szFramerate, NULL);
	//av_dict_set(&options,"offset_x","20",0);
	//The distance from the top edge of the screen or desktop
	//av_dict_set(&options,"offset_y","40",0);
	//Video frame size. The default is to capture the full screen
	//av_dict_set(&options,"video_size","320x240",0);
	if (avformat_open_input(&pFormatCtx_Video, "desktop", ifmt, &options) != 0)
	{
		printf("Couldn't open input stream.（无法打开视频输入流）\n");
		return -1;
	}
	if (avformat_find_stream_info(pFormatCtx_Video, NULL)<0)
	{
		printf("Couldn't find stream information.（无法获取视频流信息）\n");
		return -1;
	}
	if (pFormatCtx_Video->streams[0]->codec->codec_type != AVMEDIA_TYPE_VIDEO)
	{
		printf("Couldn't find video stream information.（无法获取视频流信息）\n");
		return -1;
	}
	pCodecCtx_Video = pFormatCtx_Video->streams[0]->codec;
	pCodec_Video = avcodec_find_decoder(pCodecCtx_Video->codec_id);
	if (pCodec_Video == NULL)
	{
		printf("Codec not found.（没有找到解码器）\n");
		return -1;
	}
	if (avcodec_open2(pCodecCtx_Video, pCodec_Video, NULL) < 0)
	{
		printf("Could not open codec.（无法打开解码器）\n");
		return -1;
	}

	//pCodecCtx_Video->bit_rate = 1000000;
	//pCodecCtx_Video->rc_min_rate = 128000;
	//pCodecCtx_Video->rc_max_rate = 2500000;

	img_convert_ctx = sws_getContext(pCodecCtx_Video->width, pCodecCtx_Video->height, pCodecCtx_Video->pix_fmt,
		pCodecCtx_Video->width, pCodecCtx_Video->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);

	frame_size = avpicture_get_size(pCodecCtx_Video->pix_fmt, pCodecCtx_Video->width, pCodecCtx_Video->height);
	//申请30帧缓存
	fifo_video = av_fifo_alloc(30 * avpicture_get_size(AV_PIX_FMT_YUV420P, pCodecCtx_Video->width, pCodecCtx_Video->height));

	return 0;
}

static char *dup_wchar_to_utf8(wchar_t *w)
{
	char *s = NULL;
	int l = WideCharToMultiByte(CP_UTF8, 0, w, -1, 0, 0, 0, 0);
	s = (char *)av_malloc(l);
	if (s)
		WideCharToMultiByte(CP_UTF8, 0, w, -1, s, l, 0, 0);
	return s;
}

int OpenAudioCapture()
{
	//查找输入方式
	AVInputFormat *pAudioInputFmt = av_find_input_format("dshow");

	//以Direct Show的方式打开设备，并将 输入方式 关联到格式上下文   audio=virtual-audio-capturer
	char * psDevName = dup_wchar_to_utf8(L"audio=virtual-audio-capturer");

	if (avformat_open_input(&pFormatCtx_Audio, psDevName, pAudioInputFmt, NULL) < 0)
	{
		printf("Couldn't open input stream.（无法打开音频输入流）\n");
		return -1;
	}

	if (avformat_find_stream_info(pFormatCtx_Audio, NULL)<0)
		return -1;

	if (pFormatCtx_Audio->streams[0]->codec->codec_type != AVMEDIA_TYPE_AUDIO)
	{
		printf("Couldn't find video stream information.（无法获取音频流信息）\n");
		return -1;
	}

	AVCodec *tmpCodec = avcodec_find_decoder(pFormatCtx_Audio->streams[0]->codec->codec_id);
	if (0 > avcodec_open2(pFormatCtx_Audio->streams[0]->codec, tmpCodec, NULL))
	{
		printf("can not find or open audio decoder!\n");
	}

	return 0;
}

int OpenAudioCapture_mic()
{
	//查找输入方式
	AVInputFormat *pAudioInputFmt = av