struct v4l2_format format;
memset(&format, 0, sizeof(format));
format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
format.fmt.pix.width = 320;
format.fmt.pix.height = 240;
format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
format.fmt.pix.field = V4L2_FIELD_INTERLACED;
format.fmt.pix.priv = 1;
加上这个参数:
format.fmt.pix.priv = 1;
就可以了.返回的length就不为0了