Android系统Camera预览刚打开时由暗变明

来源：互联网发布：vasp软件使用编辑：程序博客网时间：2024/06/01 08:06

http://blog.csdn.net/tankai19880619/article/details/16983627

一、回忆下V4L2驱动操作流程

1.查询驱动功能

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struct v4l2_capability cap;
ioctl(fd,VIDIOC_QUERYCAP,&cap);
printf("TK---------->>>>>Driver Name:%s\nCard Name:%s\nBus info:%s\n",cap.driver,cap.card,cap.bus_info);

2.获取当前驱动支持的视频格式

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struct v4l2_fmtdesc fmtdesc;
fmtdesc.index = 0; fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc) != -1){
printf("TK-------->>>>>fmtdesc.description is %s\n",fmtdesc.description);
fmtdesc.index ++;
}

3.设置当前驱动的频捕获格式

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struct v4l2_format fmt;
memset(&fmt,0,sizeof(fmt));
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 1280;
fmt.fmt.pix.height = 720;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
fmt.fmt.pix.field = V4L2_FIELD_NONE;//V4L2_FIELD_INTERLACED;
fmt.fmt.pix.colorspace = 8;
int fmtreslt = ioctl(fd,VIDIOC_S_FMT,&fmt);
printf("TK--------_>>>>fmtreslt is %d\n",fmtreslt);
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
//重新获取，看是否设置成功
ioctl(fd,VIDIOC_G_FMT,&fmt);
printf("TK----------->>>>>fmt.fmt.width is %d\nfmt.fmt.pix.height is %d\nfmt.fmt.pix.colorspace is %d\n",fmt.fmt.pix.width,fmt.fmt.pix.height,fmt.fmt.pix.colorspace);

4.分配内存（一般不超过5个）并转换成物理地址，将物理地址映射到用户空间

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struct v4l2_requestbuffers req;
req.count = 4;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
//分配内存
ioctl(fd,VIDIOC_REQBUFS,&req);
struct buffer{
void *start;
unsigned int length;
}*buffers;
buffers = (struct buffer*)calloc (req.count, sizeof(*buffers));
unsigned int n_buffers = 0;
for(n_buffers = 0; n_buffers < req.count; ++n_buffers){
struct v4l2_buffer buf;
memset(&buf,0,sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;
//转换成物理地址
if(ioctl(fd,VIDIOC_QUERYBUF,&buf) == -1){
printf("TK---------_>>>>>>error\n");
close(fd);
exit(-1);
}
buffers[n_buffers].length = buf.length;
//映射到用户空间
buffers[n_buffers].start = mmap(NULL,buf.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,buf.m.offset);
if(MAP_FAILED == buffers[n_buffers].start){
printf("TK--------__>>>>>error 2\n");
close(fd);
exit(-1);
}
}

5.把数据放入缓存队列

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unsigned int i;
enum v4l2_buf_type type;
for(i = 0; i < 4; i++){
struct v4l2_buffer buf;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
ioctl(fd,VIDIOC_QBUF,&buf);
}

6.开启视频流

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type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
ioctl(fd,VIDIOC_STREAMON,&type);

7.把数据从缓存队列中读取出来

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unsigned int j;
for(j = 0; j < 4; j++){
struct v4l2_buffer buf;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = 0;
ioctl(fd,VIDIOC_DQBUF,&buf);
char path[30];
snprintf(path,sizeof(path),"./v4l2test/720pmjpeg%d",buf.index);
int fdyuyv = open(path,O_WRONLY|O_CREAT,00700);
printf("TK--------->>>>fdyuyv is %d\n",fdyuyv);
int resultyuyv = write(fdyuyv,buffers[buf.index].start,1280*720*2);
printf("TK--------->>>resultyuyv is %d\n",resultyuyv);
close(fdyuyv);
}

8.关闭视频流

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ioctl(fd,VIDIOC_STREAMOFF,&type);

二、修改

原来如下——

[cpp] view plaincopy

ioctl(fd,VIDIOC_QBUF,&buf);
ioctl(fd,VIDIOC_STREAMON,&type);
ioctl(fd,VIDIOC_DQBUF,&buf);

现在改为——

[cpp] view plaincopy

ioctl(fd,VIDIOC_STREAMON,&type);
usleep(800000);
ioctl(fd,VIDIOC_QBUF,&buf);
ioctl(fd,VIDIOC_DQBUF,&buf);

其实就是刚打开时的数据不能要！！！！！

三、工程实例

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status_t V4LCameraAdapter::startPreview()
{
......
/* change by tankai
nQueued = 0;
for (int i = 0; i < mPreviewBufferCount; i++)
{
frame_count = -1;
frame_buf = (void *)mPreviewBufs.keyAt(i);
if((ret_c = getFrameRefCount(frame_buf,CameraFrame::PREVIEW_FRAME_SYNC))>=0)
frame_count = ret_c;
//if((ret_c = getFrameRefCount(frame_buf,CameraFrame::VIDEO_FRAME_SYNC))>=0)
// frame_count += ret_c;
CAMHAL_LOGDB("startPreview--buffer address:0x%x, refcount:%d",(uint32_t)frame_buf,frame_count);
if(frame_count>0)
continue;
//mVideoInfo->buf.index = i;
mVideoInfo->buf.index = mPreviewBufs.valueFor((uint32_t)frame_buf);
mVideoInfo->buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
mVideoInfo->buf.memory = V4L2_MEMORY_MMAP;
#ifdef AMLOGIC_USB_CAMERA_SUPPORT
if(mIsDequeuedEIOError){
CAMHAL_LOGEA("DQBUF EIO error has occured!\n");
return -EINVAL;
}
#endif
ret = ioctl(mCameraHandle, VIDIOC_QBUF, &mVideoInfo->buf);
if (ret < 0) {
CAMHAL_LOGEA("VIDIOC_QBUF Failed");
return -EINVAL;
}
CAMHAL_LOGDB("startPreview --length=%d, index:%d", mVideoInfo->buf.length,mVideoInfo->buf.index);
nQueued++;
}
*///end tankai
enum v4l2_buf_type bufType;
if (!mVideoInfo->isStreaming)
{
bufType = V4L2_BUF_TYPE_VIDEO_CAPTURE;
#ifdef AMLOGIC_CAMERA_NONBLOCK_SUPPORT
gettimeofday( &previewTime1, NULL);
#endif
ret = ioctl (mCameraHandle, VIDIOC_STREAMON, &bufType);
if (ret < 0) {
CAMHAL_LOGEB("StartStreaming: Unable to start capture: %s", strerror(errno));
return ret;
}
mVideoInfo->isStreaming = true;
}
if( mEnableContiFocus &&
(CAM_FOCUS_MODE_AUTO != cur_focus_mode_for_conti) &&
(CAM_FOCUS_MODE_INFINITY != cur_focus_mode_for_conti)){
struct v4l2_control ctl;
ctl.id = V4L2_CID_FOCUS_AUTO;
ctl.value = CAM_FOCUS_MODE_CONTI_VID;
if(ioctl(mCameraHandle, VIDIOC_S_CTRL, &ctl)<0){
CAMHAL_LOGDA("failed to set CAM_FOCUS_MODE_CONTI_VID!\n");
}
cur_focus_mode_for_conti = CAM_FOCUS_MODE_CONTI_VID;
}
//add by tankai
usleep(800000);
nQueued = 0;
for (int i = 0; i < mPreviewBufferCount; i++)
{
frame_count = -1;
frame_buf = (void *)mPreviewBufs.keyAt(i);
if((ret_c = getFrameRefCount(frame_buf,CameraFrame::PREVIEW_FRAME_SYNC))>=0)
frame_count = ret_c;
//if((ret_c = getFrameRefCount(frame_buf,CameraFrame::VIDEO_FRAME_SYNC))>=0)
// frame_count += ret_c;
CAMHAL_LOGDB("startPreview--buffer address:0x%x, refcount:%d",(uint32_t)frame_buf,frame_count);
if(frame_count>0)
continue;
//mVideoInfo->buf.index = i;
mVideoInfo->buf.index = mPreviewBufs.valueFor((uint32_t)frame_buf);
mVideoInfo->buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
mVideoInfo->buf.memory = V4L2_MEMORY_MMAP;
#ifdef AMLOGIC_USB_CAMERA_SUPPORT
if(mIsDequeuedEIOError){
CAMHAL_LOGEA("DQBUF EIO error has occured!\n");
return -EINVAL;
}
#endif
ret = ioctl(mCameraHandle, VIDIOC_QBUF, &mVideoInfo->buf);
if (ret < 0) {
CAMHAL_LOGEA("VIDIOC_QBUF Failed");
return -EINVAL;
}
CAMHAL_LOGDB("startPreview --length=%d, index:%d", mVideoInfo->buf.length,mVideoInfo->buf.index);
nQueued++;
}
//end tankai
......
}

补充：

看看preview线程：

[cpp] view plaincopy

int V4LCameraAdapter::previewThread()
{
uint8_t* ptr = (uint8_t*) mPreviewBufs.keyAt(mPreviewIdxs.valueFor(index)); //gralloc显存
if(mVideoInfo->buf.length != mVideoInfo->buf.bytesused){
fillThisBuffer( ptr, CameraFrame::PREVIEW_FRAME_SYNC);
/*
status_t V4LCameraAdapter::fillThisBuffer(void* frameBuf, CameraFrame::FrameType frameType)
{
ret = ioctl(mCameraHandle, VIDIOC_QBUF, &hbuf_query);//入队列
nQueued++;
}
*/
}
char *fp = this->GetFrame(index);
/*
char * V4LCameraAdapter::GetFrame(int &index)
{
ret = ioctl(mCameraHandle, VIDIOC_DQBUF, &mVideoInfo->buf); //出队列
}
*/
uint8_t* src = (uint8_t*) fp; //Camera原始数据
private_handle_t* gralloc_hnd = (private_handle_t*)ptr;
dest = (uint8_t*)gralloc_hnd->base;
if(DEFAULT_PREVIEW_PIXEL_FORMAT == V4L2_PIX_FMT_YUYV){ // 422I
frame.mLength = width*height*2;
memcpy(dest,src,frame.mLength);
}
}

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