谁在linux下用了usb摄像头

在linux下所有设备都是文件。所以对摄像头的 *** 作其实就是对文件的 *** 作。USB摄像头的设备文件就是在/dev目录下的video0(假如只有一个摄像头)。在linux下 *** 作摄像头就是使用v4l2对摄像头进行视频的 *** 作， *** 作步骤如下

1. 打开设备文件。

int fd=open(”/dev/video0″,O_RDWR)

2. 取得设备的capability，看看设备具有什么功能，比如是否具有视频输入,或者音频输入输出等。VIDIOC_QUERYCAP,struct v4l2_capability

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v4l2_std_id stddo {ret= ioctl(fd, VIDIOC_QUERYSTD, &std)} while (ret == -1 &&errno == EAGAIN)switch (std) {case V4L2_STD_NTSC://……case V4L2_STD_PAL://……}

3. 选择视频输入，一个视频设备可以有多个视频输入。VIDIOC_S_INPUT,struct v4l2_input(可不要)

4. 设置视频的制式和帧格式，制式包括PAL，NTSC，帧的格式个包括宽度和高度等。

VIDIOC_S_STD,VIDIOC_S_FMT,struct v4l2_std_id,struct v4l2_format

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struct v4l2_format fmtmemset ( &fmt, 0, sizeof(fmt) )fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTUREfmt.fmt.pix.width = 320fmt.fmt.pix.height = 240fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEGif (ioctl(fd, VIDIOC_S_FMT, &fmt) <0）{printf("set format failed\n")//return 0}

5. 向驱动申请帧缓冲，一般不超过5个。struct v4l2_requestbuffers

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struct v4l2_requestbuffers reqmemset(&req, 0, sizeof (req))req.count = 4req.type = V4L2_BUF_TYPE_VIDEO_CAPTUREreq.memory = V4L2_MEMORY_MMAPif (ioctl(fd,VIDIOC_REQBUFS,&req) == -1){perror("VIDIOC_REQBUFS error \n")//return -1}

6.申请物理内存

将申请到的帧缓冲映射到用户空间，这样就可以直接 *** 作采集到的帧了，而不必去复制。将申请到的帧缓冲全部入队列，以便存放采集到的数据.VIDIOC_QBUF,struct v4l2_buffer

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VideoBuffer* buffers = calloc( req.count, sizeof(VideoBuffer) )printf("sizeof(VideoBuffer) is %d\n",sizeof(VideoBuffer))struct v4l2_buffer buffor (numBufs = 0numBufs <req.countnumBufs++){memset( &buf, 0, sizeof(buf) )buf.type = V4L2_BUF_TYPE_VIDEO_CAPTUREbuf.memory = V4L2_MEMORY_MMAPbuf.index = numBufsif (ioctl(fd, VIDIOC_QUERYBUF, &buf) <0){printf("VIDIOC_QUERYBUF error\n")//return -1}printf("buf len is %d\n",sizeof(buf))//内存映射buffers[numBufs].length = buf.lengthbuffers[numBufs].offset = (size_t) buf.m.offsetbuffers[numBufs].start = mmap (NULL, buf.length,PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset)printf("buffers.length = %d,buffers.offset = %d ,buffers.start[0] = %d\n",buffers[numBufs].length,buffers[numBufs].offset,buffers[numBufs].start[0])printf("buf2 len is %d\n",sizeof(buffers[numBufs].start))if (buffers[numBufs].start == MAP_FAILED){perror("buffers error\n")//return -1}if (ioctl (fd, VIDIOC_QBUF, &buf) <0){printf("VIDIOC_QBUF error\n")//return -1}}

7. 开始视频的采集。

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enum v4l2_buf_type typetype = V4L2_BUF_TYPE_VIDEO_CAPTUREif (ioctl (fd, VIDIOC_STREAMON, &type) <0){printf("VIDIOC_STREAMON error\n")// return -1}

8. 出队列以取得已采集数据的帧缓冲，取得原始采集数据。VIDIOC_DQBUF, 将缓冲重新入队列尾,这样可以循环采集。VIDIOC_QBUF

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if (ioctl(fd, VIDIOC_DQBUF, &buf) <0){perror("VIDIOC_DQBUF failed.\n")//return -1}buf.type = V4L2_BUF_TYPE_VIDEO_CAPTUREbuf.memory = V4L2_MEMORY_MMAPunsigned char *ptcur = buffers[numBufs].startDEBUG("buf.bytesused = %d \n",buf.bytesused)int i1for(i1=0i1<buf.bytesusedi1++){if((buffers[numBufs].start[i1] == 0x000000FF) &&(buffers[numBufs].start[i1+1] == 0x000000C4)){DEBUG("huffman table finded! \nbuf.bytesused = %d\nFFC4 = %d \n",buf.bytesused,i1)break}}if(i1 == buf.bytesused)printf("huffman table don't exist! \n")int ifor(i=0i<buf.bytesusedi++){if((buffers[numBufs].start[i] == 0x000000FF) &&(buffers[numBufs].start[i+1] == 0x000000D8)) breakptcur++}DEBUG("i=%d,FF=%02x,D8=%02x\n",i,buffers[numBufs].start[i],buffers[numBufs].start[i+1])int imagesize =buf.bytesused - iDEBUG("buf.bytesused = %d \n",buf.bytesused)DEBUG ("imagesize = %d \n",imagesize)

9. 停止视频的采集。VIDIOC_STREAMOFF

10. 关闭视频设备。close(fd)

linux摄像头设备怎么连接电脑？

在摄像头的传输数据线接口连接到电脑的USB接口。

2.

然后在电脑的右下角就有提示更新程序驱动的提示。

3.

此时打开需要使用的摄像头程序,在这以QQ程序打开为例,在找到摄像头功能选项中单击”打开预览画面“选项。

4.

如果能打开摄像头的画面即可连接成功

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