sdl2播放网络音频直播pcm播放pcm音频流

音频直播服务是叫做 LANmic 无线话筒的安卓程序。

访问http://192.168.1.8:8080 就能播放了。可以网页播放，vlc,ffmpeg,

那么我sdl能不能播放呢？LANmic 提供了wav编码，可以直接pcm播放。

经过搜索，发现搜到的文章都是一大抄，各种转，都是一样的，sdl本地文件播放，让人头大，无奈只好自己分析方法了。

经过抓包，我发现访问http://192.168.1.8:8080 返回的是http头,后续就是riff wavefmt 搞过wav格式的都知道，这个wav头了

那么我们把http头跳过，读取后面的wav头以及数据，就可以播放了。

经过调试，代码如下

 
#include <stdio.h>
#include <tchar.h>
 
  
 
#include "SDL.h"
 #include "sockutil.h"
 
 
#pragma comment(lib, "sdl2.lib")
 
#pragma comment(lib, "SDL2main.lib")
 
Uint32  audio_len;//音频数据大小
Uint8  *audio_pos;//指向音频数据的指针
 
 
 
/**回调函数(由系统调用)
*  函数声明：typedef void (SDLCALL * SDL_AudioCallback) 
*            (void *userdata, Uint8 * stream, int len);
*  This function is called when the audio device needs more data.
*
*  userdata: An application-specific parameter saved in the SDL_AudioSpec structure(SDL_AudioSpec结构中的用户自定义数据，一般情况下可以不用)
*  stream:   A pointer to the audio data buffer.(该指针指向需要填充的音频缓冲区)
*  len:      The length of that buffer in bytes.(音频缓冲区的大小,以字节为单位)
*
*  Once the callback returns, the buffer will no longer be valid.
*  Stereo samples are stored in a LRLRLR ordering.
*
*  You can choose to avoid callbacks and use SDL_QueueAudio() instead, if
*  you like. Just open your audio device with a NULL callback.
*/
 
void  fill_audio(void *userdata, Uint8 *stream, int len)
{
	//SDL2中必须首先使用SDL_memset()将stream中的数据设置为0
	SDL_memset(stream, 0, len);
	if (audio_len == 0)		/*  Only  play  if  we  have  data  left  */
	{
		return;
	}
	len = (len > audio_len ? audio_len : len);	/*  Mix  as  much  data  as  possible  */
 
	/**
	*  函数声明：extern DECLSPEC void SDLCALL 
	*  SDL_MixAudio(Uint8 * dst, const Uint8 * src, Uint32 len, int volume);
	*  This takes two audio buffers of the playing audio format and mixes
	*  them, performing addition, volume adjustment, and overflow clipping.
	*  The volume ranges from 0 - 128, and should be set to ::SDL_MIX_MAXVOLUME
	*  for full audio volume.  Note this does not change hardware volume.
	*  This is provided for convenience -- you can mix your own audio data.
	*
	*  #define SDL_MIX_MAXVOLUME 128
	*/
 
	SDL_MixAudio(stream, audio_pos, len, SDL_MIX_MAXVOLUME);
	audio_pos += len;
	audio_len -= len;
}
 
 
 
 
 
int play()
{
  
	//初始化SDL
	if (SDL_Init(SDL_INIT_AUDIO))
	{
		printf("Could not initialize SDL - %s\n", SDL_GetError());
		return -1;
	}
 
	//SDL_AudioSpec初始化
	SDL_AudioSpec wanted_spec;
	wanted_spec.freq = 44100;			//音频数据的采样率（常用的有48000,44100等）
	wanted_spec.format = AUDIO_S16SYS;//音频数据的格式
	wanted_spec.channels = 1;			//声道数（例如单声道取值为1，立体声取值为2）
	wanted_spec.silence = 0;			//设置静音的值
	wanted_spec.samples = 1024;		//音频缓冲区中的采样个数（要求必须是2的n次方）
	wanted_spec.callback = fill_audio;//填充音频缓冲区的回调函数
 
	//打开音频
	if (SDL_OpenAudio(&wanted_spec, NULL) < 0)
	{
		printf("can't open audio.\n");
		return -1;
	}
 
	//注释掉的是文件播放.
	//FILE *fp_pcm = fopen("aa.wav", "rb");
	//if (fp_pcm == NULL)
	//{
	//	printf("cannot open this file\n");
	//	return -1;
	//}
 
 
 
	SOCK_INIT
	char target[255]=	  "192.168.1.8";
	// Connect to server.
	SOCKET c = SockLib::ConnectTarget(target,8080);
	if ( c == INVALID_SOCKET ) {
		printf("Connected to server %s err  \n", target );
		return 0;
	}
 
	printf("Connected to server %s  \n", target );
 
 
 
	std::string httpheader="" ;
	int ct=0;
	while(1)
	{
		char buf[1025]="";
		
 
 
		int ret=recv(c,buf,1,0);
		if(ret<0) return 1;
		
		httpheader +=buf[0];
 
		ct+=ret;
 
		int i=IsHTTPRequestComplete(httpheader.c_str(),ct); //有http结束标志,说明接收完.
		if (i>0)
		{
			 
	 
			break;
		}
 
	 
	}
	//跳过http头,后面就是RIFF的wav数据了。
 
 
	Sleep(1000);
 
 
 
	int pcm_buffer_size = 4096;//每次读取4096字节的数据，同时也是音频帧大小
	char *pcm_buffer = (char *)malloc(pcm_buffer_size);
	int data_count = 0;
 
	//播放音频数据
	SDL_PauseAudio(0);
 
	while (true)
	{
		//int ret = fread(pcm_buffer, 1, pcm_buffer_size, fp_pcm);
		bool ret = SockLib::RecvBuff( c, (BYTE*)pcm_buffer,  pcm_buffer_size );
		if (ret ==false)
		{
			//这里有可能是会有剩余音频数据的，不知道这样改对不对？
			audio_pos = (Uint8 *)pcm_buffer;
			audio_len = ret;
			while (audio_len > 0)
			{
				SDL_Delay(1);
			}
 
			//退出
			break;
			
			//循环播放
		//	fseek(fp_pcm, 0, SEEK_SET);
		//	fread(pcm_buffer, 1, pcm_buffer_size, fp_pcm);
		 
			data_count = 0;
		}
		printf("Now Playing %10d Bytes data.\n", data_count);
		data_count += pcm_buffer_size;
		
 
		audio_pos = (Uint8 *)pcm_buffer;
		//Audio buffer length 
		audio_len = pcm_buffer_size;
		
 
		while (audio_len > 0)//Wait until finish
		{
			SDL_Delay(1);
		}
	}
	free(pcm_buffer);
//	fclose(fp_pcm);
	SDL_Quit();
 
	return -1;
}
int _tmain(int argc, _TCHAR* argv[])
{
	while(1)
	{
		play();
		
	}
	return 0;
}

来源：oschina

链接：https://my.oschina.net/u/2397441/blog/1928236

标签

sdl