上一篇文章主要是参照AwesomePlayer直接用SoftwareRenderer类来显示yuv，为了能用到这个类，不惜依赖了libstagefright、libstagefright_color_conversion等动态静态库，从而造成程序具有很高的耦合度，也不便于我们理解yuv数据直接显示的深层次原因。

    于是我开始研究SoftwareRenderer的具体实现，我们来提取SoftwareRenderer的核心代码，自己来实现yuv的显示。

    SoftwareRenderer就只有三个方法，一个构造函数，一个析构函数，还有一个负责显示的render方法。构造方法里有个很重要的地方native_window_set_buffers_geometry这里是配置即将申请的图形缓冲区的宽高和颜色空间，忽略了这个地方，画面将用默认的值显示，将造成显示不正确。render函数里最重要的三个地方，一个的dequeBuffer，一个是mapper，一个是queue_buffer。

native_window_set_buffers_geometry;//设置宽高以及颜色空间yuv420
native_window_dequeue_buffer_and_wait;//根据以上配置申请图形缓冲区
mapper.lock(buf->handle, GRALLOC_USAGE_SW_WRITE_OFTEN, bounds, &dst));//将申请到的图形缓冲区跨进程映射到用户空间
memcpy(dst, data, dst_y_size + dst_c_size*2);//填充yuv数据到图形缓冲区
mNativeWindow->queueBuffer;//显示

有了以上分析，我们直接上代码：(yuv数据下载地址点击打开链接，放到sdcard)

main.cpp

#include <cutils/memory.h>

#include <unistd.h>
#include <utils/Log.h>

#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <binder/IServiceManager.h>
#include <media/stagefright/foundation/ADebug.h>
#include <gui/Surface.h>
#include <gui/SurfaceComposerClient.h>
#include <gui/ISurfaceComposer.h>
#include <ui/DisplayInfo.h>
#include <android/native_window.h>
#include <system/window.h>
#include <ui/GraphicBufferMapper.h>
//ANativeWindow 就是surface，对应surface.cpp里的code
using namespace android;

//将x规整为y的倍数,也就是将x按y对齐
static int ALIGN(int x, int y) {
    // y must be a power of 2.
    return (x + y - 1) & ~(y - 1);
}

void render(
        const void *data, size_t size, const sp<ANativeWindow> &nativeWindow,int width,int height) {
    sp<ANativeWindow> mNativeWindow = nativeWindow;
    int err;
	int mCropWidth = width;
	int mCropHeight = height;
	
	int halFormat = HAL_PIXEL_FORMAT_YV12;//颜色空间
    int bufWidth = (mCropWidth + 1) & ~1;//按2对齐
    int bufHeight = (mCropHeight + 1) & ~1;
	
	CHECK_EQ(0,
            native_window_set_usage(
            mNativeWindow.get(),
            GRALLOC_USAGE_SW_READ_NEVER | GRALLOC_USAGE_SW_WRITE_OFTEN
            | GRALLOC_USAGE_HW_TEXTURE | GRALLOC_USAGE_EXTERNAL_DISP));

    CHECK_EQ(0,
            native_window_set_scaling_mode(
            mNativeWindow.get(),
            NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW));

    // Width must be multiple of 32???
	//很重要,配置宽高和和指定颜色空间yuv420
	//如果这里不配置好，下面deque_buffer只能去申请一个默认宽高的图形缓冲区
    CHECK_EQ(0, native_window_set_buffers_geometry(
                mNativeWindow.get(),
                bufWidth,
                bufHeight,
                halFormat));
	
	
	ANativeWindowBuffer *buf;//描述buffer
	//申请一块空闲的图形缓冲区
    if ((err = native_window_dequeue_buffer_and_wait(mNativeWindow.get(),
            &buf)) != 0) {
        ALOGW("Surface::dequeueBuffer returned error %d", err);
        return;
    }

    GraphicBufferMapper &mapper = GraphicBufferMapper::get();

    Rect bounds(mCropWidth, mCropHeight);

    void *dst;
    CHECK_EQ(0, mapper.lock(//用来锁定一个图形缓冲区并将缓冲区映射到用户进程
                buf->handle, GRALLOC_USAGE_SW_WRITE_OFTEN, bounds, &dst));//dst就指向图形缓冲区首地址

    if (true){
        size_t dst_y_size = buf->stride * buf->height;
        size_t dst_c_stride = ALIGN(buf->stride / 2, 16);//1行v/u的大小
        size_t dst_c_size = dst_c_stride * buf->height / 2;//u/v的大小
        
        memcpy(dst, data, dst_y_size + dst_c_size*2);//将yuv数据copy到图形缓冲区
    }

    CHECK_EQ(0, mapper.unlock(buf->handle));

    if ((err = mNativeWindow->queueBuffer(mNativeWindow.get(), buf,
            -1)) != 0) {
        ALOGW("Surface::queueBuffer returned error %d", err);
    }
    buf = NULL;
}

bool getYV12Data(const char *path,unsigned char * pYUVData,int size){
	FILE *fp = fopen(path,"rb");
	if(fp == NULL){
		printf("read %s fail !!!!!!!!!!!!!!!!!!!\n",path);
		return false;
	}
	fread(pYUVData,size,1,fp);
	fclose(fp);
	return true;
}

int main(void){
	// set up the thread-pool
    sp<ProcessState> proc(ProcessState::self());
    ProcessState::self()->startThreadPool();
	
	// create a client to surfaceflinger
    sp<SurfaceComposerClient> client = new SurfaceComposerClient();
	sp<IBinder> dtoken(SurfaceComposerClient::getBuiltInDisplay(
            ISurfaceComposer::eDisplayIdMain));
	DisplayInfo dinfo;
	//获取屏幕的宽高等信息
    status_t status = SurfaceComposerClient::getDisplayInfo(dtoken, &dinfo);
	printf("w=%d,h=%d,xdpi=%f,ydpi=%f,fps=%f,ds=%f\n", 
        dinfo.w, dinfo.h, dinfo.xdpi, dinfo.ydpi, dinfo.fps, dinfo.density);
    if (status)
        return -1;
	//创建surface
    sp<SurfaceControl> surfaceControl = client->createSurface(String8("testsurface"),
            dinfo.w, dinfo.h, PIXEL_FORMAT_RGBA_8888, 0);
			
/*************************get yuv data from file;****************************************/			
	printf("[%s][%d]\n",__FILE__,__LINE__);
	int width,height;
	width = 320;
	height = 240;
	int size = width * height * 3/2;
	unsigned char *data = http://www.mamicode.com/new unsigned char[size];>
Android.mk (这次依赖的库少了很多)
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_SRC_FILES:= 	main.cpp
	
LOCAL_SHARED_LIBRARIES := 	libcutils 	libutils 	libbinder     libui     libgui 	libstagefright_foundation
	
LOCAL_MODULE:= MyShowYUV

LOCAL_MODULE_TAGS := tests

include $(BUILD_EXECUTABLE)
转载请注明出处http://blog.csdn.net/tung214/article/details/37651825