本文共 5938 字,大约阅读时间需要 19 分钟。
研究了一段时间Android的surface系统,一直执着地认为所有在surface或者屏幕上显示的画面,必须要转换成RGB才能显示,yuv数据也要通过颜色空间转换成RGB才能显示。可最近在研究stagefright视频显示时发现,根本找不到omx解码后的yuv是怎么转换成RGB的代码,yuv数据在render之后就找不到去向了,可画面确确实实的显示出来了,这从此颠覆了yuv必须要转换成RGB才能显示的真理了。
稍微看一下AsomePlayer的代码,不难发现,视频的每一帧是通过调用了SoftwareRenderer来渲染显示的,我也尝试用利用SoftwareRenderer来直接render yuv数据显示,竟然成功了,这是一个很大的突破,比如以后摄像头采集到的yuv,可以直接丢yuv数据到surface显示,无需耗时耗效率的yuv转RGB了。
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;
- native_window_dequeue_buffer_and_wait;
- mapper.lock(buf->handle, GRALLOC_USAGE_SW_WRITE_OFTEN, bounds, &dst));
- memcpy(dst, data, dst_y_size + dst_c_size*2);
- mNativeWindow->queueBuffer;
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,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>
-
- using namespace android;
-
-
- static int ALIGN(int x, int y) {
-
- 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;
- int bufWidth = (mCropWidth + 1) & ~1;
- 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));
-
-
-
-
- CHECK_EQ(0, native_window_set_buffers_geometry(
- mNativeWindow.get(),
- bufWidth,
- bufHeight,
- halFormat));
-
-
- ANativeWindowBuffer *buf;
-
- 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(
- buf->handle, GRALLOC_USAGE_SW_WRITE_OFTEN, bounds, &dst));
-
- if (true){
- size_t dst_y_size = buf->stride * buf->height;
- size_t dst_c_stride = ALIGN(buf->stride / 2, 16);
- size_t dst_c_size = dst_c_stride * buf->height / 2;
-
- memcpy(dst, data, dst_y_size + dst_c_size*2);
- }
-
- 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){
-
- sp<ProcessState> proc(ProcessState::self());
- ProcessState::self()->startThreadPool();
-
-
- sp<SurfaceComposerClient> client = new SurfaceComposerClient();
- sp<IBinder> dtoken(SurfaceComposerClient::getBuiltInDisplay(
- ISurfaceComposer::eDisplayIdMain));
- DisplayInfo dinfo;
-
- 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;
-
- sp<SurfaceControl> surfaceControl = client->createSurface(String8("testsurface"),
- dinfo.w, dinfo.h, PIXEL_FORMAT_RGBA_8888, 0);
-
-
- 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);
-
-
- SurfaceComposerClient::openGlobalTransaction();
- surfaceControl->setLayer(100000);
- surfaceControl->setPosition(100, 100);
- surfaceControl->setSize(width, height);
- SurfaceComposerClient::closeGlobalTransaction();
- sp<Surface> surface = surfaceControl->getSurface();
- printf("[%s][%d]\n",__FILE__,__LINE__);
-
-
- render(data,size,surface,width,height);
- printf("[%s][%d]\n",__FILE__,__LINE__);
-
- IPCThreadState::self()->joinThreadPool();
- IPCThreadState::self()->stopProcess();
- return 0;
- }
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
感谢这篇文章总结:http://blog.csdn.net/crazyman2010/article/details/41750623