ffmpeg实战教程（二）用SDL播放YUV，并结合ffmpeg实现简易播放器

我们先实现用SDL播放YUV数据

先来了解一下基本概念

SDL基本函数：

[初始化]

* SDL_Init(): 初始化SDL。

* SDL_CreateWindow(): 创建窗口（Window）。

* SDL_CreateRenderer(): 基于窗口创建渲染器（Render）。

* SDL_CreateTexture(): 创建纹理（Texture）。

[循环渲染数据]

* SDL_UpdateTexture(): 设置纹理的数据。

* SDL_RenderCopy(): 纹理复制给渲染器。

* SDL_RenderPresent(): 显示。

C中的fseek函数

int fseek( FILE *stream, long offset, int origin );

第一个参数stream为文件指针

第二个参数offset为偏移量，整数表示正向偏移，负数表示负向偏移

第三个参数origin设定从文件的哪里开始偏移,可能取值为：SEEK_CUR、 SEEK_END 或 SEEK_SET

SEEK_SET： 文件开头

SEEK_CUR： 当前位置

SEEK_END： 文件结尾

其中SEEK_SET,SEEK_CUR和SEEK_END和依次为0，1和2.

简言之：

fseek(fp,100L,0);把fp指针移动到离文件开头100字节处；

fseek(fp,100L,1);把fp指针移动到离文件当前位置100字节处；

fseek(fp,100L,2);把fp指针退回到离文件结尾100字节处。

下面看一下运行效果：



下面看源代码 注释很详细

#include <stdio.h>

extern "C"
{
#include "sdl/SDL.h"
};

const int bpp=12;

int screen_w=500,screen_h=500;
const int pixel_w=1920,pixel_h=1080;

unsigned char buffer[pixel_w*pixel_h*bpp/8];

//Refresh Event
#define REFRESH_EVENT  (SDL_USEREVENT + 1)

#define BREAK_EVENT  (SDL_USEREVENT + 2)

int thread_exit=0;

int refresh_video(void *opaque){
thread_exit=0;
while (!thread_exit) {
SDL_Event event;
event.type = REFRESH_EVENT;
SDL_PushEvent(&event); //发送事件 即handler
SDL_Delay(40);
}
thread_exit=0;
//Break
SDL_Event event;//代表一个事件 声明
event.type = BREAK_EVENT;
SDL_PushEvent(&event);

return 0;
}

int main(int argc, char* argv[])
{
if(SDL_Init(SDL_INIT_VIDEO)) {  //初始化SDL系统
printf( "Could not initialize SDL - %s\n", SDL_GetError());
return -1;
}

SDL_Window *screen;
//SDL 2.0  创建窗口（Window）。
screen = SDL_CreateWindow("WS Video Play SDL2", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
screen_w, screen_h,SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
if(!screen) {
printf("SDL: could not create window - exiting:%s\n",SDL_GetError());
return -1;
}
//创建基于窗口创建渲染器（Render）
SDL_Renderer* sdlRenderer = SDL_CreateRenderer(screen, -1, 0);

Uint32 pixformat=0;

//IYUV: Y + U + V  (3 planes)
//YV12: Y + V + U  (3 planes)
pixformat= SDL_PIXELFORMAT_IYUV;
//创建纹理（Texture）
SDL_Texture* sdlTexture = SDL_CreateTexture(sdlRenderer,pixformat, SDL_TEXTUREACCESS_STREAMING,pixel_w,pixel_h);

FILE *fp=NULL;
//用我们上篇博客解码出来的yuv文件
fp=fopen("output.yuv","rb+");

if(fp==NULL){
printf("cannot open this file\n");
return -1;
}
//window 视频显示框
SDL_Rect sdlRect;

SDL_Thread *refresh_thread = SDL_CreateThread(refresh_video,NULL,NULL);//创建线程
SDL_Event event;
while(1){
//Wait等待事件 即监听
SDL_WaitEvent(&event);
if(event.type==REFRESH_EVENT){
if (fread(buffer, 1, pixel_w*pixel_h*bpp/8, fp) != pixel_w*pixel_h*bpp/8){
// Loop
fseek(fp, 0, SEEK_SET);
fread(buffer, 1, pixel_w*pixel_h*bpp/8, fp);
}
//设置纹理的数据
SDL_UpdateTexture( sdlTexture, NULL, buffer, pixel_w);

//FIX: If window is resize
sdlRect.x = 0;
sdlRect.y = 0;
sdlRect.w = screen_w;
sdlRect.h = screen_h;

SDL_RenderClear( sdlRenderer );
//将纹理的数据拷贝给渲染器
SDL_RenderCopy( sdlRenderer, sdlTexture, NULL, &sdlRect);
//显示
SDL_RenderPresent( sdlRenderer );

}else if(event.type==SDL_WINDOWEVENT){
//If Resize SDL_WINDOWEVENT事件 可以拉伸播放器界面
SDL_GetWindowSize(screen,&screen_w,&screen_h);
}else if(event.type==SDL_QUIT){
thread_exit=1;
}else if(event.type==BREAK_EVENT){
break;
}
}
SDL_Quit();//退出系统
return 0;
}

我们把上篇博客解码出来的YUV数据拷贝到项目跟目录，然后编译运行即可

配置环境以及编译运行部分看 此系列的实战（一）

http://blog.csdn.net/king1425/article/details/71160339

下面我们结合上篇博客 把MP4解码为YUV，然后在SDL上播放。这样一个简易版的视频播放器就出现了

我们把一个MP4文件拷贝到项目跟目录 命名为ws.mp4

然后运行源码文件

看效果图：

#include <stdio.h>

#define __STDC_CONSTANT_MACROS

#ifdef _WIN32
//Windows
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "SDL2/SDL.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <SDL2/SDL.h>
#ifdef __cplusplus
};
#endif
#endif

//Refresh Event
#define SFM_REFRESH_EVENT  (SDL_USEREVENT + 1)

#define SFM_BREAK_EVENT  (SDL_USEREVENT + 2)

int thread_exit=0;
int thread_pause=0;

int sfp_refresh_thread(void *opaque){
thread_exit=0;
thread_pause=0;

while (!thread_exit) {
if(!thread_pause){
SDL_Event event;
event.type = SFM_REFRESH_EVENT;
SDL_PushEvent(&event);
}
SDL_Delay(40);
}
thread_exit=0;
thread_pause=0;
//Break
SDL_Event event;
event.type = SFM_BREAK_EVENT;
SDL_PushEvent(&event);

return 0;
}

int main(int argc, char* argv[])
{

AVFormatContext *pFormatCtx;
int             i, videoindex;
AVCodecContext  *pCodecCtx;
AVCodec         *pCodec;
AVFrame *pFrame,*pFrameYUV;
uint8_t *out_buffer;
AVPacket *packet;
int ret, got_picture;

//------------SDL----------------
int screen_w,screen_h;
SDL_Window *screen;
SDL_Renderer* sdlRenderer;
SDL_Texture* sdlTexture;
SDL_Rect sdlRect;
SDL_Thread *video_tid;
SDL_Event event;

struct SwsContext *img_convert_ctx;

char filepath[]="ws.mp4";

av_register_all();
avformat_network_init();
pFormatCtx = avformat_alloc_context();

if(avformat_open_input(&pFormatCtx,filepath,NULL,NULL)!=0){
printf("Couldn't open input stream.\n");
return -1;
}
if(avformat_find_stream_info(pFormatCtx,NULL)<0){
printf("Couldn't find stream information.\n");
return -1;
}
videoindex=-1;
for(i=0; i<pFormatCtx->nb_streams; i++)
if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
videoindex=i;
break;
}
if(videoindex==-1){
printf("Didn't find a video stream.\n");
return -1;
}
pCodecCtx=pFormatCtx->streams[videoindex]->codec;
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL){
printf("Codec not found.\n");
return -1;
}
if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){
printf("Could not open codec.\n");
return -1;
}
pFrame=av_frame_alloc();
pFrameYUV=av_frame_alloc();
out_buffer=(uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));
avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);

//Output Info-----------------------------
printf("---------------- File Information ---------------\n");
av_dump_format(pFormatCtx,0,filepath,0);
printf("-------------------------------------------------\n");

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

if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
printf( "Could not initialize SDL - %s\n", SDL_GetError());
return -1;
}
//SDL 2.0 Support for multiple windows
screen_w = pCodecCtx->width;
screen_h = pCodecCtx->height;
screen = SDL_CreateWindow("WS ffmpeg player", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
500, 500,SDL_WINDOW_OPENGL);

if(!screen) {
printf("SDL: could not create window - exiting:%s\n",SDL_GetError());
return -1;
}
sdlRenderer = SDL_CreateRenderer(screen, -1, 0);
//IYUV: Y + U + V  (3 planes)
//YV12: Y + V + U  (3 planes)
sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING,pCodecCtx->width,pCodecCtx->height);

sdlRect.x=0;
sdlRect.y=0;
sdlRect.w=screen_w;
sdlRect.h=screen_h;

packet=(AVPacket *)av_malloc(sizeof(AVPacket));

video_tid = SDL_CreateThread(sfp_refresh_thread,NULL,NULL);
//------------SDL End------------
//Event Loop

for (;;) {
//Wait
SDL_WaitEvent(&event);
if(event.type==SFM_REFRESH_EVENT){
//------------------------------
if(av_read_frame(pFormatCtx, packet)>=0){
if(packet->stream_index==videoindex){
ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
if(ret < 0){
printf("Decode Error.\n");
return -1;
}
if(got_picture){
sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
//SDL---------------------------
SDL_UpdateTexture( sdlTexture, NULL, pFrameYUV->data[0], pFrameYUV->linesize[0] );
SDL_RenderClear( sdlRenderer );
//SDL_RenderCopy( sdlRenderer, sdlTexture, &sdlRect, &sdlRect );
SDL_RenderCopy( sdlRenderer, sdlTexture, NULL, NULL);
SDL_RenderPresent( sdlRenderer );
//SDL End-----------------------
}
}
av_free_packet(packet);
}else{
//Exit Thread
thread_exit=1;
}
}else if(event.type==SDL_KEYDOWN){
//Pause
if(event.key.keysym.sym==SDLK_SPACE)
thread_pause=!thread_pause;
}else if(event.type==SDL_QUIT){
thread_exit=1;
}else if(event.type==SFM_BREAK_EVENT){
break;
}

}

sws_freeContext(img_convert_ctx);

SDL_Quit();
//--------------
av_frame_free(&pFrameYUV);
av_frame_free(&pFrame);
avcodec_close(pCodecCtx);
avformat_close_input(&pFormatCtx);

return 0;
}