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。

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=%fn",
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;
}

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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