基于Qt开发平台，利用linux下视频采集驱动V4L2，实现视频的采集

#include "videocapture_test.h" #include "ui_videocapture_test.h" #include <QDebug> #include <QMessageBox> #include "interface.h" #define CLEAR(x) memset(&(x), 0, sizeof(x)) QString dev_name = "/dev/video0"; VideoCapture_Test::VideoCapture_Test(QWidget *parent) : QWidget(parent), ui(new Ui::VideoCapture_Test) { ui->setupUi(this); open_flag = 0; init_Video(); start_capturing(); // p = (unsigned char *)malloc(640 * 480/*QWidget::width()*QWidget::height()*/* 3 * sizeof(char)); frame = new QImage(p,640,480,QImage::Format_RGB888); ui->VideoLab->setStyleSheet("background-color: rgb(0, 0, 0);"); timer1 = new QTimer(this); connect(timer1,SIGNAL(timeout()),this,SLOT(VideoUpdate())); connect(this,SIGNAL(display_error(QString )),this,SLOT(error_display(QString))); } void VideoCapture_Test::VideoUpdate() { // qDebug()<<"update"; int ret; ret = get_frame((void **)&p,&len); // convert_yuv_to_rgb_buffer(p,pp,640,480/*QWidget::width(),QWidget::height()*/); frame->loadFromData((uchar *)p,/*len*/640 * 480 *2 * sizeof(char)); ui->VideoLab->setPixmap(QPixmap::fromImage(*frame,Qt::AutoColor)); ui->VideoLab->update(); ret = unget_frame(); } int VideoCapture_Test::init_Video() { // int ret; v4l2_capability cap; v4l2_cropcap cropcap; v4l2_crop crop; v4l2_format fmt; // QString s = "GGGGGGGGGgg"; fd = open(dev_name.toStdString().c_str(), O_RDWR/*|O_NONBLOCK*/, 0); if(-1 == fd) { emit display_error(tr("open: %1").arg(QString(strerror(errno)))); //// emit display_error(QString(strerror(errno))); // emit display_error(s); // qDebug()<<errno; return -1; } if(-1 == ioctl(fd, VIDIOC_QUERYCAP, &cap)) { //查询设备功能 if(EINVAL == errno) { emit display_error(tr("%1 is no V4l2 device").arg(dev_name)); } else { emit display_error(tr("VIDIOC_QUERYCAP: %1").arg(QString(strerror(errno)))); } return -1; } if(!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) { //视频采集 emit display_error(tr("%1 is no video capture device").arg(dev_name)); return -1; } if(!(cap.capabilities & V4L2_CAP_STREAMING)) { //视频流 emit display_error(tr("%1 does not support streaming i/o").arg(dev_name)); return -1; } CLEAR(cropcap); cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(0 == ioctl(fd, VIDIOC_CROPCAP, &cropcap)) { CLEAR(crop); crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; crop.c = cropcap.defrect; if(-1 == ioctl(fd, VIDIOC_S_CROP, &crop)) { if(EINVAL == errno) { emit display_error(tr("VIDIOC_S_CROP not supported")); } else { emit display_error(tr("VIDIOC_S_CROP: %1").arg(QString(strerror(errno)))); return -1; } } }else{ emit display_error(tr("VIDIOC_CROPCAP: %1").arg(QString(strerror(errno)))); return -1; } /* struct v4l2_fmtdesc fmtt; memset(&fmtt, 0, sizeof(fmtt)); fmtt.index = 0; fmtt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; while ((ret = ioctl(fd, VIDIOC_ENUM_FMT, &fmtt)) == 0) { fmtt.index++; printf("{ pixelformat = ''%c%c%c%c'', description = ''%s'' }\n", fmtt.pixelformat & 0xFF, (fmtt.pixelformat >> 8) & 0xFF, (fmtt.pixelformat >> 16) & 0xFF, (fmtt.pixelformat >> 24) & 0xFF, fmtt.description); // qDebug()<<""; }*/ CLEAR(fmt); fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; fmt.fmt.pix.width = 640; fmt.fmt.pix.height = 480; // fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;//YUV4:2:2 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG ; fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;//隔行扫描 if(-1 == ioctl(fd, VIDIOC_S_FMT, &fmt)) { //设置视频格式 emit display_error(tr("VIDIOC_S_FMT").arg(QString(strerror(errno)))); return -1; } if(-1 == init_mmap()) { //初始化mmap，内存映射 return -1; } return 0; } //初始化mmap int VideoCapture_Test::init_mmap() { v4l2_requestbuffers req; CLEAR(req); req.count = 4; req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; req.memory = V4L2_MEMORY_MMAP; if(-1 == ioctl(fd, VIDIOC_REQBUFS, &req)) { //请求buf if(EINVAL == errno) { emit display_error(tr("%1 does not support memory mapping").arg(dev_name)); return -1; } else { emit display_error(tr("VIDIOC_REQBUFS %1").arg(QString(strerror(errno)))); return -1; } } if(req.count < 2) { emit display_error(tr("Insufficient buffer memory on %1").arg(dev_name)); return -1; } buffers = (buffer*)calloc(req.count, sizeof(*buffers));//分配内存大小 if(!buffers) { emit display_error(tr("out of memory")); return -1; } for(n_buffers = 0; n_buffers < req.count; ++n_buffers) { v4l2_buffer buf; CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = n_buffers; if(-1 == ioctl(fd, VIDIOC_QUERYBUF, &buf)) { //获取buf信息起始位置，长度等 emit display_error(tr("VIDIOC_QUERYBUF: %1").arg(QString(strerror(errno)))); return -1; } buffers[n_buffers].length = buf.length; buffers[n_buffers].start = mmap(NULL, // start anywhere buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);//映射 if(MAP_FAILED == buffers[n_buffers].start) { emit display_error(tr("mmap %1").arg(QString(strerror(errno)))); return -1; } } qDebug()<<"n_buffers is "<<n_buffers; return 0; } //开始捕获视频 int VideoCapture_Test::start_capturing() { unsigned int i; for(i = 0; i < n_buffers; ++i) { v4l2_buffer buf; CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory =V4L2_MEMORY_MMAP; buf.index = i; // fprintf(stderr, "n_buffers: %d\n", i); if(-1 == ioctl(fd, VIDIOC_QBUF, &buf)) { //把buf排成一列 emit display_error(tr("VIDIOC_QBUF: %1").arg(QString(strerror(errno)))); return -1; } } v4l2_buf_type type; type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(-1 == ioctl(fd, VIDIOC_STREAMON, &type)) { emit display_error(tr("VIDIOC_STREAMON: %1").arg(QString(strerror(errno)))); return -1; } return 0; } //获取一帧图像 int VideoCapture_Test::get_frame(void **frame_buf, size_t* len) { v4l2_buffer queue_buf; CLEAR(queue_buf); queue_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; queue_buf.memory = V4L2_MEMORY_MMAP; if(-1 == ioctl(fd, VIDIOC_DQBUF, &queue_buf)) { //从队列中取出一个buf switch(errno) { case EAGAIN: // perror("dqbuf"); return -1; case EIO: return -1 ; default: emit display_error(tr("VIDIOC_DQBUF: %1").arg(QString(strerror(errno)))); return -1; } } *frame_b