SDL2.0学习

http://www.ffmpeg.org/download.html

http://doc.okbase.net/leixiaohua1020/archive/110977.html  //视频

http://blog.csdn.net/leixiaohua1020/article/details/46890259 //音频

安装：

sudo apt-get install mercurial

hg clone https://hg.libsdl.org/SDL SDL2.0

该安装包不包括SDL_image , SDL_ttf, SDL_mixer

SDL播放视频的代码流程如下所示。
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。

上篇文章分析了该流程中的第4个函数SDL_CreateTexture()。本文继续分析该流程中的第5个函数SDL_UpdateTexture()。

 {
     SDL_Window *screen;
     SDL_Renderer* sdlRenderer;
     SDL_Texture* sdlTexture;
     SDL_Rect sdlRect;

     if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
         printf( "Could not initialize SDL - %s\n", SDL_GetError());
         return -;
     }

     screen = SDL_CreateWindow("Simplest ffmpeg player's Window",     SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
         screen_w, screen_h,
         SDL_WINDOW_OPENGL);

     sdlRenderer = SDL_CreateRenderer(screen, -, );
     //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);

 #if 0
     SDL_UpdateTexture( sdlTexture, NULL, pFrameYUV->data[], pFrameYUV->linesize[] );
 #else
     SDL_UpdateYUVTexture(sdlTexture, &sdlRect,
                 pFrameYUV->data[], pFrameYUV->linesize[],
                 pFrameYUV->data[], pFrameYUV->linesize[],
                 pFrameYUV->data[], pFrameYUV->linesize[]);
 #endif
     SDL_RenderClear( sdlRenderer );
     SDL_RenderCopy( sdlRenderer, sdlTexture,  NULL, &sdlRect);
     SDL_RenderPresent( sdlRenderer );
     SDL_Delay();
 }

音频：

typedef struct SDL_AudioSpec
{
    int freq;                   /**< DSP frequency -- samples per second */
    SDL_AudioFormat format;     /**< Audio data format */
    Uint8 channels;             /**< Number of channels: 1 mono, 2 stereo */
    Uint8 silence;              /**< Audio buffer silence value (calculated) */
    Uint16 samples;             /**< Audio buffer size in samples (power of 2) */
    Uint16 padding;             /**< Necessary for some compile environments */
    Uint32 size;                /**< Audio buffer size in bytes (calculated) */
    SDL_AudioCallback callback; /**< Callback that feeds the audio device (NULL to use SDL_QueueAudio()). */
    void *userdata;             /**< Userdata passed to callback (ignored for NULL callbacks). */
} SDL_AudioSpec audio;

SDL_OpenAudio（）; 打开音频

SDL_PauseAudio(0); play

SDL_MixAudio(stream,audio_pos,len,SDL_MIX_MAXVOLUME);

播放音频的例子

 #include <stdio.h>
 #include "SDL2/SDL.h"

 //Buffer:
 //|-----------|-------------|
 //chunk-------pos---len-----|
 static  unsigned char *audio_chunk;
 static  unsigned int audio_len;
 static  unsigned char *audio_pos;

 /* Audio Callback
  * The audio function callback takes the following parameters:
  * stream: A pointer to the audio buffer to be filled
  * len: The length (in bytes) of the audio buffer
  *
  */
 void  fill_audio(void *udata,unsigned char *stream,int len){
     //SDL 2.0
     SDL_memset(stream, , len);
     if(audio_len==)        /*  Only  play  if  we  have  data  left  */
         return;
     len=(len>audio_len?audio_len:len);   /*  Mix  as  much  data  as  possible  */

     SDL_MixAudio(stream,audio_pos,len,SDL_MIX_MAXVOLUME);
     audio_pos += len;
     audio_len -= len;
 }
 int main(int argc, char* argv[])
 {
     //Init
     if(SDL_Init(SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
         printf( "Could not initialize SDL - %s\n", SDL_GetError());
         return -;
     }
     //SDL_AudioSpec
     SDL_AudioSpec wanted_spec;
     wanted_spec.freq = ;
     wanted_spec.format = AUDIO_S16SYS;
     wanted_spec.channels = ;
     wanted_spec.silence = ;
     wanted_spec.samples = ;
     wanted_spec.callback = fill_audio;

     if (SDL_OpenAudio(&wanted_spec, NULL)<){
         printf("can't open audio.\n");
         return -;
     }

     FILE *fp=fopen("output.pcm","rb+");
     if(fp==NULL){
         printf("cannot open this file\n");
         return -;
     }

     int pcm_buffer_size=;
     char *pcm_buffer=(char *)malloc(pcm_buffer_size);
     int data_count=;
     //Play
     SDL_PauseAudio();

     while(){
         if (fread(pcm_buffer, , pcm_buffer_size, fp) != pcm_buffer_size){
             // Loop
             fseek(fp, , SEEK_SET);
             fread(pcm_buffer, , pcm_buffer_size, fp);
             data_count=;
         }
         printf("Now Playing %10d Bytes data.\n",data_count);
         data_count+=pcm_buffer_size;
         //Set audio buffer (PCM data)
         audio_chunk = (unsigned char*) pcm_buffer;
         //Audio buffer length
         audio_len =pcm_buffer_size;
         audio_pos = audio_chunk;

         while(audio_len>)//Wait until finish
             SDL_Delay();
     }
     free(pcm_buffer);
     SDL_Quit();
     return ;