Android用surface直接顯示yuv數據（二）

上一篇文章主要是參照AwesomePlayer直接用SoftwareRenderer類來顯示yuv，爲了能用到這個類，不惜依賴了libstagefright、libstagefright_color_conversion等動態靜態庫，從而造成程序具有很高的耦合度，也不便於我們理解yuv數據直接顯示的深層次原因。

    於是我開始研究SoftwareRenderer的具體實現，我們來提取SoftwareRenderer的核心代碼，自己來實現yuv的顯示。

    SoftwareRenderer就只有三個方法，一個構造函數，一個析構函數，還有一個負責顯示的render方法。構造方法裏有個很重要的地方native_window_set_buffers_geometry這裏是配置即將申請的圖形緩衝區的寬高和顏色空間，忽略了這個地方，畫面將用默認的值顯示，將造成顯示不正確。render函數裏最重要的三個地方，一個的dequeBuffer，一個是mapper，一個是queue_buffer。

native_window_set_buffers_geometry;//設置寬高以及顏色空間yuv420
native_window_dequeue_buffer_and_wait;//根據以上配置申請圖形緩衝區
mapper.lock(buf->handle, GRALLOC_USAGE_SW_WRITE_OFTEN, bounds, &dst));//將申請到的圖形緩衝區跨進程映射到用戶空間
memcpy(dst, data, dst_y_size + dst_c_size*2);//填充yuv數據到圖形緩衝區
mNativeWindow->queueBuffer;//顯示

以上五步是surface顯示圖形必不可少的五步。

有了以上分析，我們直接上代碼：(yuv數據下載地址點擊打開鏈接，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，對應surface.cpp裏的code
using namespace android;

//將x規整爲y的倍數,也就是將x按y對齊
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;//顏色空間
    int bufWidth = (mCropWidth + 1) & ~1;//按2對齊
    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,配置寬高和和指定顏色空間yuv420
    //如果這裏不配置好，下面deque_buffer只能去申請一個默認寬高的圖形緩衝區
    CHECK_EQ(0, native_window_set_buffers_geometry(
                mNativeWindow.get(),
                bufWidth,
                bufHeight,
                halFormat));


    ANativeWindowBuffer *buf;//描述buffer
    //申請一塊空閒的圖形緩衝區
    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(//用來鎖定一個圖形緩衝區並將緩衝區映射到用戶進程
                buf->handle, GRALLOC_USAGE_SW_WRITE_OFTEN, bounds, &dst));//dst就指向圖形緩衝區首地址

    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);//將yuv數據copy到圖形緩衝區
    }

    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;
    //獲取屏幕的寬高等信息
    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;
    //創建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);//設定Z座標
    surfaceControl->setPosition(100, 100);//以左上角爲(0,0)設定顯示位置
    surfaceControl->setSize(width, height);//設定視頻顯示大小
    SurfaceComposerClient::closeGlobalTransaction();
    sp<Surface> surface = surfaceControl->getSurface();
    printf("[%s][%d]\n",__FILE__,__LINE__);

/**********************顯示yuv數據******************************************************************/
    render(data,size,surface,width,height);
    printf("[%s][%d]\n",__FILE__,__LINE__);

    IPCThreadState::self()->joinThreadPool();//可以保證畫面一直顯示，否則瞬間消失
    IPCThreadState::self()->stopProcess();
    return 0;
}

Android.mk (這次依賴的庫少了很多)

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)

轉載請註明出處http://blog.csdn.net/tung214/article/details/37651825