Android用surface直接显示yuv数据（二）

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。

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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

以上五步是surface显示图形必不可少的五步。

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

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#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 = new unsigned char[size];

const char *path = "/mnt/sdcard/yuv_320_240.yuv";

getYV12Data(path,data,size);//get yuv data from file;

/*********************配置surface*******************************************************************/

SurfaceComposerClient::openGlobalTransaction();

surfaceControl->setLayer(100000);//设定Z坐标

surfaceControl->setPosition(100, 100);//以左上角为(0,0)设定显示位置

surfaceControl->setSize(width, height);//设定视频显示大小

SurfaceComposerClient::closeGlobalTransaction();

sp<Surface> surface = surfaceControl->getSurface();

printf("[%s][%d]\n",__FILE__,__LINE__);

/**********************显示yuv数据******************************************************************/

render(data,size,surface,width,height);

printf("[%s][%d]\n",__FILE__,__LINE__);

IPCThreadState::self()->joinThreadPool();//可以保证画面一直显示，否则瞬间消失

IPCThreadState::self()->stopProcess();

return 0;

}

Android.mk (这次依赖的库少了很多)

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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)

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