原：http://blog.csdn.net/danjuan123/article/details/65444098

SDL（Simple Directmedia Layer）是一套开源的跨平台多媒体开发库，集成了音视频的许多底层的API，介绍Windows平台下的例子已经很多了，例如：雷老师的 最简单的视音频播放示例7：SDL2播放RGB/YUV,既然SDL是跨平台的，自己有参考了雷老师的这篇文章 最简单的基于FFmpeg的移动端例子附件：SDL Android HelloWorld,下面将介绍下Android平台上播放视频的简单的例子 ,

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SDL结构框图

SDL4Android中接口都是使用C语言写的，接口调用使用的是Java，android调用c的接口需要用到jni（Java native interface）技术,需要先将c接口编译成共享库.so文件，目前可以使用两种工具进行编译：ndk和cmake(android-studio2.2以后的版本才支持cmake编译)，下面的框图显示的是使用ndk工具编译SDL的接口： 

SDL的文件源码主要分为两部分，一部分是java代码，主要包含有Android上层使用的SDLActivity上层接口调用函数；另一部分就是SDL-jni，包含所有SDL底层的源码、自定义的接口源码以及将这些源码编译成共享库所需的Android.mk文件。

如图中所示，SDL_android.c和SDL_android_mian.c是官方demo中编译官方接口的c源文件，其中SDL_android.c编译21个接口放在libSDL2.so共享库中；在此次使用SDL播放视频的Demo中，SDL_android_mian.c配合我们自定义的Custom.c(可以定义多个或者一个文件)只编译一个nativeInit()接口放在libmain.so共享库中

下载SDL源码

SDL的介绍就不多说了，详细可以访问SDL官方网站,推荐一个中文学习网站SDL中文教程,但是里面的API版本是1.2的，可以了解一下，还有就是外文的教程网站Lazy Foo,利用SDL播放视频，推荐访问雷老师的博客。

截至2017年2月，SDL版本已经更新到2.05，点击官方下载地址 

github上也可以下载github下载地址

在android工程中我需要用到的源码,android-project、include、src三个文件夹

android-project中主要是官方的demo：jni文件夹中需要配置.mk编译文件，src文件夹中包含官方的android上层java代码；  include和src中就是SDL的底层C代码，编译之后方可被上层java调用。

合并ffmpeg和SDL源码

因为我们解码用到的是ffmepg，所以此次还要集成ffmpeg的源码，不了解ffmpeg的移植的话，可以查看我前面写的文章:第一次完成FFmepg的移植，编译ffmpeg4Android

为了减少代码的层级，我把SDL的源码和FFmepg的源码混合了在一起了

调用c函数的流程

SDL打开视频播放的过程实际上是创建一个SDLActivity的过程,SDLActivity会创建一个SDLSurface和一个layout布局,然后将SDLSurface添加到布局上面，视频画面就是在SDLSurface上显示出来，正如上图中，SDLSurface要调用nativeInit函数，必须先通过JNI实现图像解码显示功能

我们对nativeInit函数稍作修改，在SDLActivity中把视频的URI传给nativeInt函数，

SDLActivity.java声明中，

public static native int nativeInit(String string); 1 1

SDL_android_main.c中，

/* This prototype is needed to prevent a warning about the missing prototype for global function below */ JNIEXPORT int JNICALL Java_com_righere_convexdplayer_sdl_SDLActivity_nativeInit(JNIEnv* env, jclass cls, jstring string); /* Start up the SDL app */ JNIEXPORT int JNICALL Java_com_righere_convexdplayer_sdl_SDLActivity_nativeInit(JNIEnv* env, jclass cls, jstring string) { int i; int argc = 3; int status; // int len; char* argv[3]; /* This interface could expand with ABI negotiation, callbacks, etc. */ SDL_Android_Init(env, cls); SDL_SetMainReady(); argv[0] = SDL_strdup("app_process"); const char* utf = NULL; if(string){ utf = (*env)->GetStringUTFChars(env, string, 0); if(utf){ argv[1] = SDL_strdup(utf); (*env)->ReleaseStringUTFChars(env, string, utf); } } argv[2] = NULL; //argv[0] = "app_progress" argv[1] = string argv[2] = NULL /* Run the application. */ status = SDL_main(argc, argv); /* Release the arguments. */ for (i = 0; i < argc; i++) { SDL_free(argv[i]); } SDL_stack_free(argv); /* Do not issue an exit or the whole application will terminate instead of just the SDL thread */ /* exit(status); */ return status; } 12345678910111213141516171819202122232425262728293031323334353637383940414243444546 12345678910111213141516171819202122232425262728293031323334353637383940414243444546

编写C源文件实现

先看下FFmpeg的解码和SDL的显示流程： 

// // Created by righere on 16-11-22. // #include "stdio.h" #ifdef __ANDROID__ #include <jni.h> #include <android/log.h> //使用NDK的log #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,"ERROR: ", __VA_ARGS__) #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,"INFO: ", __VA_ARGS__) #else #define LOGE(format, ...) printf("ERROR: " format "\n",###__VA_ARGS__) #define LOGI(format, ...) printf("INFO: " format "\n",###__VA_ARGS__) #endif #include <src/render/SDL_sysrender.h> #include <src/video/SDL_sysvideo.h> #include <libavutil/imgutils.h> #include "SDL.h" #include "libavcodec/avcodec.h" #include "libavfilter/avfilter.h" #include "libavformat/avformat.h" #include "libswscale/swscale.h" //屏幕参数 int SCREEN_W = 1920; int SCREEN_H = 1080; //设置buffer输出格式，YUV：1， RGB：0 #define BUFFER_FMT_YUV 0 int main(int argc, char** argv) { //FFmpeg Parameters AVFormatContext *pFormatCtx; int streamIdx; AVCodecContext *pCodecCtx; AVCodecParameters *avCodecParameters; AVCodec *pCodec; AVFrame *pFrame, *pFrame_out; AVPacket *packet; //size buffer uint8_t *out_buffer; static struct SwsContext *img_convert_ctx; //SDL Parameters SDL_Window *sdlWindow; SDL_Texture *sdlTexture; SDL_Rect sdlRect; SDL_Renderer *renderer; if(argc < 2) { LOGE("no media input!"); return -1; } //获取文件名 const char* mediaUri = (const char *) argv[1]; av_register_all();//注册所有支持的文件格式以及编解码器 //分配一个AVFormatContext pFormatCtx = avformat_alloc_context(); //判断文件流是否能打开 if(avformat_open_input(&pFormatCtx, mediaUri, NULL, NULL) != 0){ LOGE("Couldn't open input stream! \n"); return -1; } //判断能够找到文件流信息 if(avformat_find_stream_info(pFormatCtx, NULL) < 0){ LOGE("couldn't find open stream information !\n"); return -1; } //打印文件信息 av_dump_format(pFormatCtx, -1, mediaUri, 0); streamIdx=-1; for(int i=0; i<pFormatCtx->nb_streams; i++) //新版本ffmpeg将AVCodecContext *codec替换成*codecpar if(pFormatCtx->streams[i]->codecpar->codec_type==AVMEDIA_TYPE_VIDEO) { streamIdx=i; break; } if(streamIdx == -1){ LOGE("Couldn't find a video stream !\n"); return -1; } // Get a pointer to the codec context for the video stream avCodecParameters = pFormatCtx->streams[streamIdx]->codecpar; // Find the decoder for the video stream pCodec=avcodec_find_decoder(avCodecParameters->codec_id); if(pCodec){ LOGI("find decoder: %d", avCodecParameters->codec_id); } //alloc a codecContext pCodecCtx = avcodec_alloc_context3(pCodec); //transform if(avcodec_parameters_to_context(pCodecCtx,avCodecParameters) < 0){ LOGE("copy the codec parameters to context fail!"); return -1; } //打开codec int errorCode = avcodec_open2(pCodecCtx, pCodec, NULL); if(errorCode < 0){ LOGE("Unable to open codec!\n"); return errorCode; }; //alloc frame of ffmpeg decode pFrame = av_frame_alloc(); if(pFrame == NULL){ LOGE("Unable to allocate an AVFrame!\n"); return -1; } //decode packet packet = av_packet_alloc(); pFrame_out = av_frame_alloc(); #if BUFFER_FMT_YUV //output frame for SDL enum AVPixelFormat pixel_fmt = AV_PIX_FMT_YUV420P; #else //output RGBFrame enum AVPixelFormat pixel_fmt = AV_PIX_FMT_RGBA; #endif out_buffer = av_malloc((size_t) av_image_get_buffer_size(pixel_fmt,pCodecCtx->width,pCodecCtx->height,1)); av_image_fill_arrays(pFrame_out->data,pFrame_out->linesize, out_buffer, pixel_fmt,pCodecCtx->width,pCodecCtx->height,1); //transform size and format of CodecCtx,立方插值 img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, pixel_fmt, SWS_BICUBIC, NULL, NULL, NULL); //初始化SDL if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) { LOGE("SDL_Init failed %s" ,SDL_GetError()); exit(1); } //设置window属性 sdlWindow = SDL_CreateWindow("Convexd_SDL",SDL_WINDOWPOS_UNDEFINED,SDL_WINDOWPOS_UNDEFINED, SCREEN_W, SCREEN_H,SDL_WINDOW_RESIZABLE|SDL_WINDOW_FULLSCREEN|SDL_WINDOW_OPENGL); if(!sdlWindow) { LOGE("SDL: could not set video mode - exiting\n"); exit(1); } //create renderer and set parameter renderer = SDL_CreateRenderer(sdlWindow,-1,0); #if BUFFER_FMT_YUV Uint32 sdl_out_fmt = SDL_PIXELFORMAT_IYUV; #else Uint32 sdl_out_fmt = SDL_PIXELFORMAT_RGBA32; #endif //Allocate a place to put our yuv image on that screen,set sdl_display_resolution sdlTexture = SDL_CreateTexture(renderer, sdl_out_fmt,SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height); //默认全屏可以不用设置 // sdlRect.x = 0; // sdlRect.y = 0; // sdlRect.w = SCREEN_W; // sdlRect.h = SCREEN_H; // Read frames while (av_read_frame(pFormatCtx, packet) >= 0) { // Is this a packet from the video stream? if (packet->stream_index == streamIdx) { //decoder allocate frame to pFrame,new api LOGI("%s","Got Video Packet Succeed"); int getPacketCode = avcodec_send_packet(pCodecCtx, packet); if(getPacketCode == 0) { int getFrameCode = avcodec_receive_frame(pCodecCtx, pFrame); LOGI("%d", getFrameCode); // Did we get a video frame? if (getFrameCode == 0) { LOGI("%s", "Got Video Frame Succeed"); //scale Frame sws_scale(img_convert_ctx, (const uint8_t *const *) pFrame->data, pFrame->linesize, 0, pFrame->height, pFrame_out->data, pFrame_out->linesize); #if (BUFFER_FMT_YUV == 1) SDL_UpdateYUVTexture(sdlTexture, NULL, pFrame_out->data[0], pFrame_out->linesize[0], pFrame_out->data[1],pFrame_out->linesize[1], pFrame_out->data[2],pFrame_out->linesize[2]); #else SDL_UpdateTexture(sdlTexture,NULL,pFrame_out->data[0],pCodecCtx->width*4); //4通道：pitch = width×4 #endif SDL_RenderClear(renderer); SDL_RenderCopy(renderer, sdlTexture, NULL, NULL); SDL_RenderPresent(renderer); //Delay 40ms，25FPS SDL_Delay(40); } else if (getFrameCode == AVERROR(EAGAIN)) { LOGE("%s", "Frame is not available right now,please try another input"); } else if (getFrameCode == AVERROR_EOF) { LOGE("%s", "the decoder has been fully flushed"); } else if (getFrameCode == AVERROR(EINVAL)) { LOGE("%s", "codec not opened, or it is an encoder"); } else { LOGI("%s", "legitimate decoding errors"); } } } // Free the packet that was allocated by av_read_frame av_packet_unref(packet); } sws_freeContext(img_convert_ctx); av_frame_free(&pFrame_out); av_frame_free(&pFrame); avcodec_close(pCodecCtx); avformat_close_input(&pFormatCtx); SDL_Quit(); return 0; } 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242

编写Android.mk文件

先新建一个自定义的c源文件convexd_native_render.c,我们的视频的解码和显示都会在这里面实现。  此工程中的Android.mk文件在移植ffmepg的Android.mk文件的基础上增加了编译libSDL2main.so和libSDL2.so的配置，如下：

########################### # # SDL static library # ########################### LOCAL_MODULE := SDL2_static LOCAL_MODULE_FILENAME := libSDL2 LOCAL_SRC_FILES += $(LOCAL_PATH)/src/main/android/SDL_android_main.c LOCAL_LDLIBS := LOCAL_EXPORT_LDLIBS := -Wl,--undefined=Java_com_righere_convexdplayer_sdl_SDLActivity_nativeInit -ldl -lGLESv1_CM -lGLESv2 -llog -landroid include $(BUILD_STATIC_LIBRARY) ########################### # # SDL My Custom library # add by ldq 20161122 # ########################### include $(CLEAR_VARS) LOCAL_MODULE := SDL2main LOCAL_C_INCLUDES := $(LOCAL_PATH)/include \ LOCAL_EXPORT_C_INCLUDES := $(LOCAL_C_INCLUDES) # Add your application source files here... LOCAL_SRC_FILES := $(LOCAL_PATH)/src/main/android/SDL_android_main.c \ $(LOCAL_PATH)/convexd_native_render.c LOCAL_SHARED_LIBRARIES := SDL2 avcodec avfilter avformat avutil swresample swscale LOCAL_LDLIBS := -lGLESv1_CM -lGLESv2 -llog include $(BUILD_SHARED_LIBRARY) 123456789101112131415161718192021222324252627282930313233343536373839404142 123456789101112131415161718192021222324252627282930313233343536373839404142

可以根据自己的路径配置mk文件

配置build.gradle

android{ defaultConfig { ndk { abiFilter("armeabi") moduleName "SDL2main" ldLibs "log", "z", "m", "jnigraphics", "android" } } externalNativeBuild { ndkBuild { path 'src/main/jni/Android.mk' } } } 12345678910111213141516 12345678910111213141516

实现播放

在手机根目录下新建一个convexd的文件夹，把播放视频放进去，打开我们打包的demo，选择视频就可以实现视频的播放功能。

[附上demo地址]：https://github.com/righere/ConvexdSDLPlayer.git