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
", SDL_GetError());
        return -1; 
    }

    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, -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);

#if 0
    SDL_UpdateTexture( sdlTexture, NULL, pFrameYUV->data[0], pFrameYUV->linesize[0] );
#else
    SDL_UpdateYUVTexture(sdlTexture, &sdlRect,
                pFrameYUV->data[0], pFrameYUV->linesize[0],
                pFrameYUV->data[1], pFrameYUV->linesize[1],
                pFrameYUV->data[2], pFrameYUV->linesize[2]);
#endif
    SDL_RenderClear( sdlRenderer );
    SDL_RenderCopy( sdlRenderer, sdlTexture,  NULL, &sdlRect);
    SDL_RenderPresent( sdlRenderer );
    SDL_Delay(40);
}

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, 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  */

    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
", SDL_GetError());
        return -1;
    }
    //SDL_AudioSpec
    SDL_AudioSpec wanted_spec;
    wanted_spec.freq = 44100;
    wanted_spec.format = AUDIO_S16SYS;
    wanted_spec.channels = 2;
    wanted_spec.silence = 0;
    wanted_spec.samples = 1024;
    wanted_spec.callback = fill_audio;

    if (SDL_OpenAudio(&wanted_spec, NULL)<0){
        printf("can't open audio.
");
        return -1;
    }

    FILE *fp=fopen("output.pcm","rb+");
    if(fp==NULL){
        printf("cannot open this file
");
        return -1;
    }

    int pcm_buffer_size=4096;
    char *pcm_buffer=(char *)malloc(pcm_buffer_size);
    int data_count=0;
    //Play
    SDL_PauseAudio(0);

    while(1){
        if (fread(pcm_buffer, 1, pcm_buffer_size, fp) != pcm_buffer_size){
            // Loop
            fseek(fp, 0, SEEK_SET);
            fread(pcm_buffer, 1, pcm_buffer_size, fp);
            data_count=0;
        }
        printf("Now Playing %10d Bytes data.
",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>0)//Wait until finish
            SDL_Delay(1);
    }
    free(pcm_buffer);
    SDL_Quit();
    return 0;