SDL音视频渲染

01-SDL简介

官网：https://www.libsdl.org/
文档：http://wiki.libsdl.org/Introduction

SDL（Simple DirectMedia Layer）是一套开放源代码的跨平台多媒体开发库，使用C语言写成。SDL提供了数种控制图像、声音、输出入的函数，让开发者只要用相同或是相似的代码就可以开发出跨多个平台（Linux、Windows、Mac OS X等）的应用软件。目前SDL多用于开发游戏、模拟器、媒体播放器等多媒体应用领域。

02-Windows环境搭建

下载地址：https://www.libsdl.org/download-2.0.php

先直接下载dll和lib使用

MinGW：Minimalist GNU for Windows

案例

将SDL2-2.0.10拷贝到工程目录
将 SDL2-2.0.10\lib\x86 下的 SDL2.dll 拷贝到工程目录

.prcwin32 {INCLUDEPATH += $$PWD/SDL2-2.0.10/includeLIBS += $$PWD/SDL2-2.0.10/lib/x86/SDL2.lib
}

main.c#include <stdio.h>#include <SDL.h>#undef mainint main()
{printf("Hello World!\n");SDL_Window *window = NULL;      // 声明窗口SDL_Init(SDL_INIT_VIDEO);       // 初始化SDL// 创建SDL Windowwindow = SDL_CreateWindow("Basic Window",           // 标题SDL_WINDOWPOS_UNDEFINED,  // xSDL_WINDOWPOS_UNDEFINED,  // y640,                      // 宽480,                      // 高SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);// 类型if(!window) // 检测是否创建成功{printf("创建 window 失败, err:%s\n", SDL_GetError());return 1;}SDL_Delay(10000);  // 延迟10000msSDL_DestroyWindow(window); // 销毁窗口SDL_Quit(); // 释放资源return 0;
}

03-Linux环境搭建

下载地址：https://www.libsdl.org/download-2.0.php

1. 下载SDL源码库，SDL2-2.0.10.tar.gz
2. 解压，然后依次执行命令
   ./configure
   make
   sudo make install.
3. 如果出现Could not initialize SDL - No available video device(Did you set the DISPLAY variable?)错误
   说明系统中没有安装x11的库文件，因此编译出来的SDL库实际上不能用。
   下载安装
   sudo apt-get install libx11-dev
   sudo apt-get install xorg-dev

04-SDL子系统

SDL将功能分成下列数个子系统（subsystem）：
◼ SDL_INIT_TIMER：定时器
◼ SDL_INIT_AUDIO：音频
◼ SDL_INIT_VIDEO：视频
◼ SDL_INIT_JOYSTICK：摇杆
◼ SDL_INIT_HAPTIC：触摸屏
◼ SDL_INIT_GAMECONTROLLER：游戏控制器
◼ SDL_INIT_EVENTS：事件
◼ SDL_INIT_EVERYTHING：包含上述所有选项

05-SDL Window显示：SDL视频显示函数简介

◼ SDL_Init()：初始化SDL系统
◼ SDL_CreateWindow()：创建窗口SDL_Window
◼ SDL_CreateRenderer()：创建渲染器SDL_Renderer
◼ SDL_CreateTexture()：创建纹理SDL_Texture
◼ SDL_UpdateTexture()：设置纹理的数据
◼ SDL_RenderCopy()：将纹理的数据拷贝给渲染器
◼ SDL_RenderPresent()：显示
◼ SDL_Delay()：工具函数，用于延时
◼ SDL_Quit()：退出SDL系统

06-SDL Windows显示：SDL数据结构简介

◼ SDL_Window 代表了一个“窗口”
◼ SDL_Renderer 代表了一个“渲染器”
◼ SDL_Texture 代表了一个“纹理”
◼ SDL_Rect 一个简单的矩形结构

存储RGB和存储纹理的区别：
比如一个从左到右由红色渐变到蓝色的矩形，用存储RGB的话就需要把矩形中每个点的具体颜色值存储下来；而纹理只是一些描述信息，比如记录了矩形的大小、起始颜色、终止颜色等信息，显卡可以通过这些信息推算出矩形块的详细信息。
所以相对于存储RGB而已，存储纹理占用的内存要少的多。

案例

新建工程 02-sdl-window
将SDL2-2.0.10拷贝到工程目录
将 SDL2-2.0.10\lib\x86 下的 SDL2.dll 拷贝到工程目录

.prcwin32 {INCLUDEPATH += $$PWD/SDL2-2.0.10/includeLIBS += $$PWD/SDL2-2.0.10/lib/x86/SDL2.lib
}

main.c#include <stdio.h>
#include <SDL.h>#undef mainint main()
{int run = 1;SDL_Window *window = NULL;SDL_Renderer *renderer = NULL;SDL_Texture *texture = NULL;SDL_Rect rect; // 长方形，原点在左上角rect.w = 50;    //方块大小rect.h = 50;SDL_Init(SDL_INIT_VIDEO);//初始化函数,可以确定希望激活的子系统window = SDL_CreateWindow("2 Window",SDL_WINDOWPOS_UNDEFINED,SDL_WINDOWPOS_UNDEFINED,640,480,SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);// 创建窗口if (!window){return -1;}renderer = SDL_CreateRenderer(window, -1, 0);//基于窗口创建渲染器if (!renderer){return -1;}texture = SDL_CreateTexture(renderer,SDL_PIXELFORMAT_RGBA8888,SDL_TEXTUREACCESS_TARGET,640,480); //创建纹理if (!texture){return -1;}int show_count = 0;while (run){rect.x = rand() % 600;rect.y = rand() % 400;SDL_SetRenderTarget(renderer, texture); // 设置渲染目标为纹理SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255); // 纹理背景为黑色SDL_RenderClear(renderer); //清屏SDL_RenderDrawRect(renderer, &rect); //绘制一个长方形SDL_SetRenderDrawColor(renderer, 0, 255, 255, 255); //长方形为白色SDL_RenderFillRect(renderer, &rect);SDL_SetRenderTarget(renderer, NULL); //恢复默认，渲染目标为窗口SDL_RenderCopy(renderer, texture, NULL, NULL); //拷贝纹理到CPUSDL_RenderPresent(renderer); //输出到目标窗口上SDL_Delay(300);if(show_count++ > 30){run = 0;        // 不跑了}}SDL_DestroyTexture(texture);SDL_DestroyRenderer(renderer);SDL_DestroyWindow(window); //销毁窗口SDL_Quit();return 0;
}

运行

07-SDL事件

SDL事件

◼ 函数
• SDL_WaitEvent()：等待一个事件
• SDL_PushEvent()：发送一个事件
• SDL_PumpEvents()：将硬件设备产生的事件放入事件队列，用于读取事件，在调用该函数之前，必须调用SDL_PumpEvents搜集键盘等事件
• SDL_PeepEvents()：从事件队列提取一个事件

◼ 数据结构
• SDL_Event：代表一个事件

案例

新建工程 03-sdl-event
将 SDL2-2.0.10和SDL2-2.0.10\lib\x86 下的 SDL2.dll 拷贝到工程目录

03-sdl-event.proTEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qtSOURCES += main.cwin32 {INCLUDEPATH += $$PWD/SDL2-2.0.10/includeLIBS += $$PWD/SDL2-2.0.10/lib/x86/SDL2.lib
}

main.c#include <stdio.h>
#include <SDL.h>#define FF_QUIT_EVENT    (SDL_USEREVENT + 2) // 用户自定义事件#undef mainint main(int argc, char* argv[])
{SDL_Window *window = NULL;              // Declare a pointerSDL_Renderer *renderer = NULL;SDL_Init(SDL_INIT_VIDEO);               // Initialize SDL2// Create an application window with the following settings:window = SDL_CreateWindow("An SDL2 window",                  // window titleSDL_WINDOWPOS_UNDEFINED,           // initial x positionSDL_WINDOWPOS_UNDEFINED,           // initial y position640,                               // width, in pixels480,                               // height, in pixelsSDL_WINDOW_SHOWN | SDL_WINDOW_BORDERLESS// flags - see below);// Check that the window was successfully createdif (window == NULL){// In the case that the window could not be made...printf("Could not create window: %s\n", SDL_GetError());return 1;}/* We must call SDL_CreateRenderer in order for draw calls to affect this window. */renderer = SDL_CreateRenderer(window, -1, 0);/* Select the color for drawing. It is set to red here. */SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);/* Clear the entire screen to our selected color. */SDL_RenderClear(renderer);/* Up until now everything was drawn behind the scenes.This will show the new, red contents of the window. */SDL_RenderPresent(renderer);SDL_Event event;int b_exit = 0;for (;;){SDL_WaitEvent(&event);switch (event.type){case SDL_KEYDOWN:   /* 键盘事件 */switch (event.key.keysym.sym){case SDLK_a:printf("key down a\n");break;case SDLK_s:printf("key down s\n");break;case SDLK_d:printf("key down d\n");break;case SDLK_q:printf("key down q and push quit event\n");SDL_Event event_q;event_q.type = FF_QUIT_EVENT;SDL_PushEvent(&event_q);break;default:printf("key down 0x%x\n", event.key.keysym.sym);break;}break;case SDL_MOUSEBUTTONDOWN:           /* 鼠标按下事件 */if (event.button.button == SDL_BUTTON_LEFT){printf("mouse down left\n");}else if(event.button.button == SDL_BUTTON_RIGHT){printf("mouse down right\n");}else{printf("mouse down %d\n", event.button.button);}break;case SDL_MOUSEMOTION:       /* 鼠标移动事件 */printf("mouse movie (%d,%d)\n", event.button.x, event.button.y);break;case FF_QUIT_EVENT:printf("receive quit event\n");b_exit = 1;break;}if(b_exit)break;}//destory rendererif (renderer)SDL_DestroyRenderer(renderer);// Close and destroy the windowif (window)SDL_DestroyWindow(window);// Clean upSDL_Quit();return 0;
}

构建项目
将 SDL2.dll 拷贝到 build-03-sdl-event-Desktop_Qt_5_10_1_MSVC2015_32bit-Debug 目录
运行

08-SDL线程

SDL多线程
◼ SDL线程创建：SDL_CreateThread
◼ SDL线程等待：SDL_WaitThead
◼ SDL互斥锁：SDL_CreateMutex/SDL_DestroyMutex
◼ SDL锁定互斥：SDL_LockMutex/SDL_UnlockMutex
◼ SDL条件变量(信号量)：SDL_CreateCond/SDL_DestoryCond
◼ SDL条件变量(信号量)等待/通知：SDL_CondWait/SDL_CondSingal

案例

新建工程 04-sdl-thread
将 SDL2-2.0.10和SDL2-2.0.10\lib\x86 下的 SDL2.dll 拷贝到工程目录

04-sdl-thread.proTEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qtSOURCES += main.cwin32 {INCLUDEPATH += $$PWD/SDL2-2.0.10/includeLIBS += $$PWD/SDL2-2.0.10/lib/x86/SDL2.lib
}

main.c#include <SDL.h>
#include <stdio.h>SDL_mutex *s_lock = NULL;
SDL_cond *s_cond = NULL;int thread_work(void *arg)
{SDL_LockMutex(s_lock);printf("                <============thread_work sleep\n");sleep(10);      // 用来测试获取锁printf("                <============thread_work wait\n");// 释放s_lock资源，并等待signal。之所以释放s_lock是让别的线程能够获取到s_lockSDL_CondWait(s_cond, s_lock); //另一个线程(1)发送signal和(2)释放lock后，这个函数退出printf("                <===========thread_work receive signal, continue to do ~_~!!!\n");printf("                <===========thread_work end\n");SDL_UnlockMutex(s_lock);return 0;
}#undef main
int main()
{s_lock = SDL_CreateMutex();s_cond = SDL_CreateCond();SDL_Thread * t = SDL_CreateThread(thread_work,"thread_work",NULL);if(!t){printf("  %s",SDL_GetError);return -1;}for(int i = 0;i< 2;i++){sleep(2);printf("main execute =====>\n");}printf("main SDL_LockMutex(s_lock) before ====================>\n");SDL_LockMutex(s_lock);  // 获取锁，但是子线程还拿着锁printf("main ready send signal====================>\n");printf("main SDL_CondSignal(s_cond) before ====================>\n");SDL_CondSignal(s_cond); // 发送信号，唤醒等待的线程printf("main SDL_CondSignal(s_cond) after ====================>\n");sleep(10);SDL_UnlockMutex(s_lock);// 释放锁，让其他线程可以拿到锁printf("main SDL_UnlockMutex(s_lock) after ====================>\n");SDL_WaitThread(t, NULL);SDL_DestroyMutex(s_lock);SDL_DestroyCond(s_cond);return 0;
}

构建项目
将 SDL2.dll 拷贝到 build-04-sdl-thread-Desktop_Qt_5_10_1_MSVC2015_32bit-Debug 目录
运行

09-SDL YUV显示：SDL视频显示的流程

案例

新建工程 05-sdl-yuv
将 SDL2-2.0.10和SDL2-2.0.10\lib\x86 下的 SDL2.dll 拷贝到工程目录

05-sdl-yuv.proTEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qtSOURCES += main.cwin32 {INCLUDEPATH += $$PWD/SDL2-2.0.10/includeLIBS += $$PWD/SDL2-2.0.10/lib/x86/SDL2.lib
}

main.c#include <stdio.h>
#include <string.h>#include <SDL.h>//自定义消息类型
#define REFRESH_EVENT   (SDL_USEREVENT + 1)     // 请求画面刷新事件
#define QUIT_EVENT      (SDL_USEREVENT + 2)     // 退出事件//定义分辨率
// YUV像素分辨率
#define YUV_WIDTH   320
#define YUV_HEIGHT  240
//定义YUV格式
#define YUV_FORMAT  SDL_PIXELFORMAT_IYUVint s_thread_exit = 0;  // 退出标志 = 1则退出int refresh_video_timer(void *data)
{while (!s_thread_exit){SDL_Event event;event.type = REFRESH_EVENT;SDL_PushEvent(&event);SDL_Delay(40);}s_thread_exit = 0;//push quit eventSDL_Event event;event.type = QUIT_EVENT;SDL_PushEvent(&event);return 0;
}
#undef main
int main(int argc, char* argv[])
{//初始化 SDLif(SDL_Init(SDL_INIT_VIDEO)){fprintf( stderr, "Could not initialize SDL - %s\n", SDL_GetError());return -1;}// SDLSDL_Event event;                            // 事件SDL_Rect rect;                              // 矩形SDL_Window *window = NULL;                  // 窗口SDL_Renderer *renderer = NULL;              // 渲染SDL_Texture *texture = NULL;                // 纹理SDL_Thread *timer_thread = NULL;            // 请求刷新线程uint32_t pixformat = YUV_FORMAT;            // YUV420P，即是SDL_PIXELFORMAT_IYUV// 分辨率// 1. YUV的分辨率int video_width = YUV_WIDTH;int video_height = YUV_HEIGHT;// 2.显示窗口的分辨率int win_width = YUV_WIDTH;int win_height = YUV_WIDTH;// YUV文件句柄FILE *video_fd = NULL;const char *yuv_path = "yuv420p_320x240.yuv";size_t video_buff_len = 0;uint8_t *video_buf = NULL; //读取数据后先把放到buffer里面// 我们测试的文件是YUV420P格式uint32_t y_frame_len = video_width * video_height;uint32_t u_frame_len = video_width * video_height / 4;uint32_t v_frame_len = video_width * video_height / 4;uint32_t yuv_frame_len = y_frame_len + u_frame_len + v_frame_len;//创建窗口window = SDL_CreateWindow("Simplest YUV Player",SDL_WINDOWPOS_UNDEFINED,SDL_WINDOWPOS_UNDEFINED,video_width, video_height,SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);if(!window){fprintf(stderr, "SDL: could not create window, err:%s\n",SDL_GetError());goto _FAIL;}// 基于窗口创建渲染器renderer = SDL_CreateRenderer(window, -1, 0);// 基于渲染器创建纹理texture = SDL_CreateTexture(renderer,pixformat,SDL_TEXTUREACCESS_STREAMING,video_width,video_height);// 分配空间video_buf = (uint8_t*)malloc(yuv_frame_len);if(!video_buf){fprintf(stderr, "Failed to alloce yuv frame space!\n");goto _FAIL;}// 打开YUV文件video_fd = fopen(yuv_path, "rb");if( !video_fd ){fprintf(stderr, "Failed to open yuv file\n");goto _FAIL;}// 创建请求刷新线程timer_thread = SDL_CreateThread(refresh_video_timer,NULL,NULL);while (1){// 收取SDL系统里面的事件SDL_WaitEvent(&event);if(event.type == REFRESH_EVENT) // 画面刷新事件{video_buff_len = fread(video_buf, 1, yuv_frame_len, video_fd);if(video_buff_len <= 0){fprintf(stderr, "Failed to read data from yuv file!\n");goto _FAIL;}// 设置纹理的数据 video_width = 320， planeSDL_UpdateTexture(texture, NULL, video_buf, video_width);// 显示区域，可以通过修改w和h进行缩放rect.x = 0;rect.y = 0;float w_ratio = win_width * 1.0 /video_width;float h_ratio = win_height * 1.0 /video_height;// 320x240 怎么保持原视频的宽高比例rect.w = video_width * w_ratio;rect.h = video_height * h_ratio;
//            rect.w = video_width * 0.5;
//            rect.h = video_height * 0.5;// 清除当前显示SDL_RenderClear(renderer);// 将纹理的数据拷贝给渲染器SDL_RenderCopy(renderer, texture, NULL, &rect);// 显示SDL_RenderPresent(renderer);}else if(event.type == SDL_WINDOWEVENT){//If ResizeSDL_GetWindowSize(window, &win_width, &win_height);printf("SDL_WINDOWEVENT win_width:%d, win_height:%d\n",win_width,win_height );}else if(event.type == SDL_QUIT) //退出事件{s_thread_exit = 1;}else if(event.type == QUIT_EVENT){break;}}_FAIL:s_thread_exit = 1;      // 保证线程能够退出// 释放资源if(timer_thread)SDL_WaitThread(timer_thread, NULL); // 等待线程退出if(video_buf)free(video_buf);if(video_fd)fclose(video_fd);if(texture)SDL_DestroyTexture(texture);if(renderer)SDL_DestroyRenderer(renderer);if(window)SDL_DestroyWindow(window);SDL_Quit();return 0;}

构建项目
将 SDL2.dll 拷贝到 build-05-sdl-yuv-Desktop_Qt_5_10_1_MinGW_32bit-Debug 目录
将 yuv420p_320x240.yuv 文件 拷贝到build-05-sdl-yuv-Desktop_Qt_5_10_1_MinGW_32bit-Debug目录

运行

10-SDL播放音频PCM-打开音频设备

打开音频设备

int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired, SDL_AudioSpec * obtained); 
// desired：期望的参数。
// obtained：实际音频设备的参数，一般情况下设置为NULL即可。

SDL_AudioSpec

typedef struct SDL_AudioSpec {int freq; // 音频采样率SDL_AudioFormat format; // 音频数据格式Uint8 channels; // 声道数: 1 单声道, 2 立体声Uint8 silence; // 设置静音的值，因为声音采样是有符号的，所以0当然就是这个值Uint16 samples; // 音频缓冲区中的采样个数，要求必须是2的n次Uint16 padding; // 考虑到兼容性的一个参数Uint32 size; // 音频缓冲区的大小，以字节为单位SDL_AudioCallback callback; // 填充音频缓冲区的回调函数void *userdata; // 用户自定义的数据
} SDL_AudioSpec;

11-SDL播放音频PCM-SDL_AudioCallback

SDL_AudioCallback

// userdata：SDL_AudioSpec结构中的用户自定义数据，一般情况下可以不用。
// stream：该指针指向需要填充的音频缓冲区。
// len：音频缓冲区的大小（以字节为单位）1024*2*2。
void (SDLCALL * SDL_AudioCallback) (void *userdata, Uint8 *stream, int len);

播放音频数据

// 当pause_on设置为0的时候即可开始播放音频数据。设置为1的时候，将会
播放静音的值。
void SDLCALL SDL_PauseAudio(int pause_on)

12-SDL播放音频PCM-代码

案例

新建工程 06-sdl-pcm
将 SDL2-2.0.10和SDL2-2.0.10\lib\x86 下的 SDL2.dll 拷贝到工程目录

06-sdl-pcm.proTEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qtSOURCES += main.cwin32 {INCLUDEPATH += $$PWD/SDL2-2.0.10/includeLIBS += $$PWD/SDL2-2.0.10/lib/x86/SDL2.lib
}

main.c/*** SDL2播放PCM** 本程序使用SDL2播放PCM音频采样数据。SDL实际上是对底层绘图* API（Direct3D，OpenGL）的封装，使用起来明显简单于直接调用底层* API。* 测试的PCM数据采用采样率44.1k, 采用精度S16SYS, 通道数2** 函数调用步骤如下:** [初始化]* SDL_Init(): 初始化SDL。* SDL_OpenAudio(): 根据参数（存储于SDL_AudioSpec）打开音频设备。* SDL_PauseAudio(): 播放音频数据。** [循环播放数据]* SDL_Delay(): 延时等待播放完成。**/#include <stdio.h>
#include <SDL.h>// 每次读取2帧数据, 以1024个采样点一帧 2通道 16bit采样点为例
#define PCM_BUFFER_SIZE (1024*2*2*2)// 音频PCM数据缓存
static Uint8 *s_audio_buf = NULL;
// 目前读取的位置
static Uint8 *s_audio_pos = NULL;
// 缓存结束位置
static Uint8 *s_audio_end = NULL;//音频设备回调函数
void fill_audio_pcm(void *udata, Uint8 *stream, int len)
{SDL_memset(stream, 0, len);if(s_audio_pos >= s_audio_end) // 数据读取完毕{return;}// 数据够了就读预设长度，数据不够就只读部分（不够的时候剩多少就读取多少）int remain_buffer_len = s_audio_end - s_audio_pos;len = (len < remain_buffer_len) ? len : remain_buffer_len;// 拷贝数据到stream并调整音量SDL_MixAudio(stream, s_audio_pos, len, SDL_MIX_MAXVOLUME/8);printf("len = %d\n", len);s_audio_pos += len;  // 移动缓存指针
}// 提取PCM文件
// ffmpeg -i input.mp4 -t 20 -codec:a pcm_s16le -ar 44100 -ac 2 -f s16le 44100_16bit_2ch.pcm
// 测试PCM文件
// ffplay -ar 44100 -ac 2 -f s16le 44100_16bit_2ch.pcm
#undef main
int main(int argc, char *argv[])
{int ret = -1;FILE *audio_fd = NULL;SDL_AudioSpec spec;const char *path = "44100_16bit_2ch.pcm";// 每次缓存的长度size_t read_buffer_len = 0;//SDL initializeif(SDL_Init(SDL_INIT_AUDIO))    // 支持AUDIO{fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());return ret;}//打开PCM文件audio_fd = fopen(path, "rb");if(!audio_fd){fprintf(stderr, "Failed to open pcm file!\n");goto _FAIL;}s_audio_buf = (uint8_t *)malloc(PCM_BUFFER_SIZE);// 音频参数设置SDL_AudioSpecspec.freq = 44100;          // 采样频率spec.format = AUDIO_S16SYS; // 采样点格式spec.channels = 2;          // 2通道spec.silence = 0;spec.samples = 1024;       // 23.2ms -> 46.4ms 每次读取的采样数量，多久产生一次回调和 samplesspec.callback = fill_audio_pcm; // 回调函数spec.userdata = NULL;//打开音频设备if(SDL_OpenAudio(&spec, NULL)){fprintf(stderr, "Failed to open audio device, %s\n", SDL_GetError());goto _FAIL;}//play audioSDL_PauseAudio(0);int data_count = 0;while(1){// 从文件读取PCM数据read_buffer_len = fread(s_audio_buf, 1, PCM_BUFFER_SIZE, audio_fd);if(read_buffer_len == 0){break;}data_count += read_buffer_len; // 统计读取的数据总字节数printf("now playing %10d bytes data.\n",data_count);s_audio_end = s_audio_buf + read_buffer_len;    // 更新buffer的结束位置s_audio_pos = s_audio_buf;  // 更新buffer的起始位置//the main thread wait for a momentwhile(s_audio_pos < s_audio_end){SDL_Delay(10);  // 等待PCM数据消耗}}printf("play PCM finish\n");// 关闭音频设备SDL_CloseAudio();_FAIL://release some resourcesif(s_audio_buf)free(s_audio_buf);if(audio_fd)fclose(audio_fd);//quit SDLSDL_Quit();return 0;
}

构建项目
将 SDL2.dll 拷贝到 build-06-sdl-pcm-Desktop_Qt_5_10_1_MinGW_32bit-Debug 目录
将 44100_16bit_2ch.pcm 文件 拷贝到 build-06-sdl-pcm-Desktop_Qt_5_10_1_MinGW_32bit-Debug 目录

运行