{"id":4988,"date":"2023-10-16T17:44:29","date_gmt":"2023-10-16T09:44:29","guid":{"rendered":"https:\/\/blog.coderfan.org\/?p=4988"},"modified":"2024-05-09T21:13:32","modified_gmt":"2024-05-09T13:13:32","slug":"acuqiring-camera-metadata-via-v4l2-apis","status":"publish","type":"post","link":"https:\/\/blog.coderfan.org\/en\/acuqiring-camera-metadata-via-v4l2-apis.html","title":{"rendered":"\u901a\u8fc7V4L2 API\u83b7\u53d6Camera\u6570\u636e"},"content":{"rendered":"
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\n \t<\/i> Read Time:<\/span>3 Minute, 42 Second <\/div>\n\n <\/div>\n

\u5f53\u6211\u4eec\u5728Linux\u6216\u8005Android\u5e73\u53f0\u5f00\u53d1Camera\u76f8\u5173\u5e94\u7528\u65f6\uff0c\u90fd\u9700\u8981\u4eceCamera\u9a71\u52a8\u4e2d\u83b7\u53d6\u5230Camera\u6570\u636e\uff0c\u7528\u4e8e\u540e\u7eed\u7684Preview\u3001Capture\u6216\u8005Snapshot\u7b49\uff0c\u6b64\u65f6\u6211\u4eec\u5f80\u5f80\u4f1a\u501f\u52a9V4L2\u6846\u67b6\u6765\u5b9e\u73b0\u3002<\/p>\n\n\n\n

V4L2\u7684\u5168\u79f0\u4e3aVideo For Linux Version Two\uff1b\u662f\u5f53\u524dLinux\u6216\u8005\u7c7bLinux\u5e73\u53f0\u4e2d\u5e7f\u6cdb\u4f7f\u7528\u7684\u591a\u5a92\u4f53\u6846\u67b6\uff0c\u4e3a\u4e0a\u5c42\u8f6f\u4ef6\u63d0\u4f9b\u591a\u79cd\u786c\u4ef6\u80fd\u529b\uff0c\u5982codec encoder\u3001decoder\uff0ccamera\u7b49\u3002V4L2\u5728\u8f6f\u4ef6\u5c42\u6b21\u4e0a\u5c5e\u4e8e\u5185\u6838\u6846\u67b6\u5c42\uff0c\u7528\u6237\u6001\u7a0b\u5e8f\u5728\u4e0eV4L2\u6846\u67b6\u8fdb\u884c\u4ea4\u4e92\u65f6\uff0c\u5f80\u5f80\u90fd\u9700\u8981\u901a\u8fc7ioctl\u7684\u7cfb\u7edf\u8c03\u7528\u6765\u5b9e\u73b0\u3002\u672c\u7bc7\u6587\u7ae0\u5c06\u6839\u636e\u5b9e\u9645\u5e94\u7528\u4e2d\u7684\u6d41\u7a0b\uff0c\u4ecb\u7ecd\u5982\u4f55\u901a\u8fc7V4L2 API\u83b7\u53d6Camera\u6570\u636e\u3002<\/p>\n\n\n\n

\u6b65\u9aa4\u4e00<\/strong>\uff1a\u901a\u8fc7open\u7cfb\u7edf\u8c03\u7528\u83b7\u53d6\u5bf9\u5e94Camera\u8bbe\u5907\u7684\u6587\u4ef6\u53e5\u67c4<\/p>\n\n\n\n

\u5728\u901a\u8fc7v4l2\u63a5\u53e3\u83b7\u53d6Camera\u6570\u636e\u524d\uff0c\u6211\u4eec\u9700\u8981\u77e5\u9053Camera\u8bbe\u5907\u7684\u8bbe\u5907\u8282\u70b9\uff1b\u63a5\u7740\u6211\u4eec\u5c31\u53ef\u4ee5\u901a\u8fc7open\u51fd\u6570\u7684\u7cfb\u7edf\u8c03\u7528\u6765\u6253\u5f00\u76f8\u5e94\u7684\u8bbe\u5907\u8282\u70b9\uff0cCamera\u7684\u8bbe\u5907\u8282\u70b9\u90fd\u4f4d\u4e8e\/dev\/video*\u4e0b\u3002<\/p>\n\n\n\n

\/\/flag O_RDWR\u8868\u660e\u53ef\u8bfb\u5199\nmDeviceFd = open(deviceName, O_RDWR, 0);<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u4e8c<\/strong>\uff1a\u901a\u8fc7ioctl\u7cfb\u7edf\u8c03\u7528\u5224\u5b9a\u662f\u5426\u662f\u6709\u6548\u7684Camera\u8bbe\u5907\u53ca\u5176\u652f\u6301\u7684\u529f\u80fd<\/p>\n\n\n\n
v4l2_capability caps;\nint result = ioctl(mDeviceFd, VIDIOC_QUERYCAP, &caps);<\/code><\/pre>\n\n\n\n
\u8fd4\u56de\u503c\u5c0f\u4e8e0\u5219\u8868\u660e\u67e5\u8be2\u5931\u8d25\uff0c\u53cd\u4e4b\u5219\u67e5\u8be2\u6210\u529f\uff1b\u5728\u67e5\u8be2\u6210\u529f\u7684\u60c5\u51b5\u4e0b\u5224\u65ad\u5176\u914d\u7f6e\u4f4d\u503c\u662f\u5426\u4e3a1\uff0c\u8fd9\u91cc\u6211\u4eec\u67e5\u8be2\u7684\u662f\u4e24\u4e2a\u914d\u7f6e\uff1aV4L2_CAP_VIDEO_CAPTURE\u3001V4L2_CAP_STREAMING\u3002\u4e00\u822c\u9700\u8981\u8fd9\u4e24\u4e2a\u914d\u7f6e\u90fd\u6ee1\u8db3\u624d\u8ba4\u4e3a\u662f\u6709\u6548\u7684Camera\u8bbe\u5907\u3002<\/p>\n\n\n\n
\u5176\u4e2dv4l2_capability\u7ed3\u6784\u4f53\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n\n\n\n
\/**\n  * struct v4l2_capability - Describes V4L2 device caps returned by VIDIOC_QUERYCAP\n  *\n  * @driver:           name of the driver module (e.g. \"bttv\")\n  * @card:     name of the card (e.g. \"Hauppauge WinTV\")\n  * @bus_info:         name of the bus (e.g. \"PCI:\" + pci_name(pci_dev) )\n  * @version:          KERNEL_VERSION\n  * @capabilities: capabilities of the physical device as a whole\n  * @device_caps:  capabilities accessed via this particular device (node)\n  * @reserved:         reserved fields for future extensions\n  *\/\nstruct v4l2_capability {\n    __u8    driver[16];\n    __u8    card[32];\n    __u8    bus_info[32];\n    __u32   version;\n    __u32   capabilities;\n    __u32   device_caps;\n    __u32   reserved[3];\n};<\/code><\/pre>\n\n\n\n
\u5982\u679c\u6211\u4eec\u662f\u5728Linux\u7cfb\u7edf\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528v4l2-ctl\u547d\u4ee4\u6765\u67e5\u770b\u67d0\u4e2aCamera\u8bbe\u5907\u652f\u6301\u7684\u5177\u4f53\u7684\u914d\u7f6e\u4fe1\u606f\uff1a<\/p>\n\n\n\n
marcus@goliat:~$ v4l2-ctl -d \/dev\/video4  --info\nDriver Info:\n    Driver name      : uvcvideo\n    Card type        : USB 2.0 Camera: USB Camera\n    Bus info         : usb-0000:00:14.0-8.3.1.1\n    Driver version   : 6.0.8\n    Capabilities     : 0x84a00001\n        Video Capture\n        Metadata Capture\n        Streaming\n        Extended Pix Format\n        Device Capabilities\n    Device Caps      : 0x04200001\n        Video Capture\n        Streaming\n        Extended Pix Format<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u4e09<\/strong>\uff1a\u901a\u8fc7ioctl\u7cfb\u7edf\u8c03\u7528\u67e5\u8be2\u5f53\u524dCamera\u8bbe\u5907\u652f\u6301\u7684\u6570\u636e\u683c\u5f0f\uff0c\u4e3a\u4e0b\u4e00\u6b65\u505a\u51c6\u5907<\/p>\n\n\n\n
v4l2_fmtdesc formatDescription;\nformatDescription.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;\nint result=ioctl(mDeviceFd, VIDIOC_ENUM_FMT, &formatDescription);<\/code><\/pre>\n\n\n\n
\u5176\u4e2dv4l2_fmtdesc\u7ed3\u6784\u4f53\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n\n\n\n
struct v4l2_fmtdesc {\n    __u32   index;\n    __u32   type;\n    __u32   flags;\n    __u32   description;\n    __u32   pixelformat;\n}<\/code><\/pre>\n\n\n\n
\u8fd4\u56de\u503c\u5c0f\u4e8e0\u5219\u67e5\u8be2\u5931\u8d25\uff0c\u53cd\u4e4b\u5219\u67e5\u8be2\u6210\u529f\uff1b\u5728\u67e5\u8be2\u6210\u529f\u65f6\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7formatDescription.pixelformat\u503c\u5224\u65ad\u5176\u652f\u6301\u7684\u683c\u5f0f\u7c7b\u578b\uff0c\u5e38\u89c1\u7684\u6570\u636e\u7c7b\u578b\u5305\u62ec\uff1a<\/p>\n\n\n\n
V4L2_PIX_FMT_YUYV\nV4L2_PIX_FMT_NV21\nV4L2_PIX_FMT_NV16\nV4L2_PIX_FMT_YVU420\nV4L2_PIX_FMT_RGB32\nV4L2_PIX_FMT_ARGB32<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u56db<\/strong>\uff1a\u8bbe\u5b9aCamera\u8bbe\u5907\u7684\u8f93\u51fa\u683c\u5f0f\uff0c\u8be5\u8f93\u51fa\u683c\u5f0f\u5fc5\u987b\u662f\u6b65\u9aa4\u4e09\u4e2d\u6240\u652f\u6301\u7684\uff1b\u4e00\u822c\u6211\u4eec\u4f1a\u6839\u636e\u5b9e\u9645\u9700\u8981\u7ed3\u5408Camera\u8bbe\u5907\u81ea\u8eab\u7684\u80fd\u529b\u8bbe\u5b9a\u5408\u9002\u7684\u8f93\u51fa\u683c\u5f0f,\u8f93\u51fa\u683c\u5f0f\u7684\u4e0d\u540c\u4f1a\u5f71\u54cd\u5230\u6570\u636e\u91cf\u7684\u5927\u5c0f\u3002<\/p>\n\n\n\n
v4l2_format format;\nformat.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;\nformat.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;\nformat.fmt.pix.width = width;\nformat.fmt.pix.height = height;\n\/\/\u8bbe\u7f6e\u6570\u636e\u683c\u5f0f\nioctl(mDeviceFd, VIDIOC_S_FMT, &format)<\/code><\/pre>\n\n\n\n
\u5728\u8fd9\u4e00\u6b65\u4e2d\uff0c\u6240\u6d89\u53ca\u5230\u7684v4l2_format\u7ed3\u6784\u4f53\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n\n\n\n
\/**\n * struct v4l2_format - stream data format\n * @type:   enum v4l2_buf_type; type of the data stream\n * @pix:    definition of an image format\n * @pix_mp: definition of a multiplanar image format\n * @win:    definition of an overlaid image\n * @vbi:    raw VBI capture or output parameters\n * @sliced: sliced VBI capture or output parameters\n * @raw_data:       placeholder for future extensions and custom formats\n * @fmt:    union of @pix, @pix_mp, @win, @vbi, @sliced, @sdr, @meta\n *          and @raw_data\n *\/\nstruct v4l2_format {\n    __u32    type;\n    union {\n        struct v4l2_pix_format              pix;     \/* V4L2_BUF_TYPE_VIDEO_CAPTURE *\/\n        struct v4l2_pix_format_mplane       pix_mp;  \/* V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE *\/\n        struct v4l2_window          win;     \/* V4L2_BUF_TYPE_VIDEO_OVERLAY *\/\n        struct v4l2_vbi_format              vbi;     \/* V4L2_BUF_TYPE_VBI_CAPTURE *\/\n        struct v4l2_sliced_vbi_format       sliced;  \/* V4L2_BUF_TYPE_SLICED_VBI_CAPTURE *\/\n        struct v4l2_sdr_format              sdr;     \/* V4L2_BUF_TYPE_SDR_CAPTURE *\/\n        struct v4l2_meta_format             meta;    \/* V4L2_BUF_TYPE_META_CAPTURE *\/\n        __u8        raw_data[200];                   \/* user-defined *\/\n    } fmt;\n};<\/code><\/pre>\n\n\n\n
\u4e00\u822c\u6211\u4eec\u8fd8\u9700\u8981\u8fdb\u884c\u4e8c\u6b21\u6821\u9a8c\uff0c\u786e\u4fdd\u8f93\u51fa\u6570\u636e\u7b26\u5408\u8981\u6c42\uff1a<\/p>\n\n\n\n
\/\/\u83b7\u53d6\u6570\u636e\u683c\u5f0f\nioctl(mDeviceFd, VIDIOC_G_FMT, &format)<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u4e94\uff1a\u7533\u8bf7Buffer\u533a\u57df\u7528\u4e8e\u63a8\u6d41<\/p>\n\n\n\n
v4l2_requestbuffers bufrequest;\nbufrequest.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;\nbufrequest.memory = V4L2_MEMORY_MMAP;\/\/\u4f7f\u7528mmap\u8fdb\u884c\u6620\u5c04\nbufrequest.count = 1;\/\/buffer\u6570\u91cf\uff0c\u4e00\u822c\u6211\u4eec\u7533\u8bf7\u4e00\u4e2a\u5373\u53ef\nioctl(mDeviceFd, VIDIOC_REQBUFS, &bufrequest)<\/code><\/pre>\n\n\n\n
\u8fd4\u56de\u503c\u5c0f\u4e8e0\u5219\u7533\u8bf7\u5931\u8d25\uff0c\u53cd\u4e4b\u5219\u6210\u529f\uff0c\u63a5\u4e0b\u6765\u6211\u4eec\u5c31\u53ef\u4ee5\u5f00\u59cb\u6784\u9020v4l2_buffer\u5bf9\u8c61\u7528\u4e8e\u63a5\u6536Camera\u6570\u636e\u4e86\u3002<\/p>\n\n\n\n
\u5176\u4e2d\u6240\u6d89\u53ca\u5230\u7684\u7ed3\u6784\u4f53v4l2_requestbuffers\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n\n\n\n
struct v4l2_requestbuffers {\n    __u32                   count;\n    __u32                   type;           \/* enum v4l2_buf_type *\/\n    __u32                   memory;         \/* enum v4l2_memory *\/\n    __u32                   capabilities;\n    __u8                    flags;\n    __u8                    reserved[3];\n};<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc\u89e3\u8bfb\u4e00\u4e0b\u51e0\u4e2a\u6bd4\u8f83\u91cd\u8981\u7684\u53c2\u6570\uff1a<\/p>\n\n\n\n
count<\/strong>:\u7528\u4e8e\u8868\u5f81buffer\u7684\u6570\u91cf\uff0c\u6211\u4eec\u9700\u8981\u5408\u9002\u7684\u6570\u91cf\uff1b\u5982\u679c\u6570\u91cf\u8bbe\u5b9a\u8fc7\u5c0f\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4driver\u5728\u586b\u5145Camera\u6570\u636e\u65f6\u6ca1\u6709\u53ef\u7528\u7684buffer\uff0c\u6570\u636e\u8bbe\u5b9a\u8fc7\u5927\u5219\u4f1a\u6d88\u8d39\u989d\u5916\u7684\u5185\u5b58\u7a7a\u95f4\u3002<\/p>\n\n\n\n
type<\/strong>:buffer\u6240\u5b58\u50a8\u7684\u6570\u636e\u7c7b\u578b\uff0c\u9488\u5bf9Camera\u8bbe\u5907\uff0c\u4e00\u822c\u6211\u4eec\u5c06\u6b64\u9879\u8bbe\u5b9a\u4e3aV4L2_BUF_TYPE_VIDEO_CAPTURE<\/em>\u3002<\/p>\n\n\n\n
memory<\/strong>:\u8bbe\u5b9a\u63a8\u6d41\u6570\u636e\u7684\u66f4\u65b0\u65b9\u5f0f\uff0c\u53ef\u9009\u503c\u5305\u62ec\uff1aV4L2_MEMORY_MMAP<\/em>\u3001V4L2_MEMORY_USERPTR \u3001V4L2_MEMORY_DMABUF<\/em>\u3002<\/p>\n\n\n\n
\u6b65\u9aa4\u516d\uff1a\u67e5\u8be2v4l2\u4e3a\u6211\u4eec\u521b\u5efa\u7684buffer\u4fe1\u606f<\/p>\n\n\n\n
v4l2_buffer buf = {0};\nbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;\nbuf.memory = V4L2_MEMORY_MMAP;\nbuf.index = 0;\/\/index\u8868\u660e\u5176\u6b21\u5e8f\nint res = ioctl(mDeviceFd, VIDIOC_QUERYBUF, &buf);<\/code><\/pre>\n\n\n\n
\u8fd4\u56de\u503c\u5c0f\u4e8e0\u5219\u8868\u660e\u67e5\u8be2\u5931\u8d25\uff0c\u53cd\u4e4b\u5219\u6210\u529f\uff0c\u6211\u4eec\u53ef\u4ee5\u5f97\u5230\u5982\u4e0b\u4fe1\u606f\uff1a<\/p>\n\n\n\n
buf.m.offset:\u504f\u79fb\u91cf\nbuf.length:\u957f\u5ea6\nbuf.flags:\u6807\u5fd7\u4f4d<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u4e03\uff1a\u901a\u8fc7mmap\u865a\u62df\u5185\u5b58\u6620\u5c04\uff0c\u5bf9\u5e94\u6b65\u9aa4\u516d\u4e2d\u7684\u8bbe\u5b9a\u7684memory\u4e3a V4L2_MEMORY_MMAP<\/em> \uff0c\u4ece\u800c\u62ff\u5230Camera\u6570\u636e\u5bf9\u5e94\u672c\u5730\u8fdb\u7a0b\u7a7a\u95f4\u5185\u7684\u6307\u9488\uff1a<\/p>\n\n\n\n
buffer = (u_int8_t*)mmap (NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, mDeviceFd, buf.m.offset);\nif(buffer == MAP_FAILED)\n{\n\treturn false;\n}\n\/\/memset\u6e050\uff0c\u907f\u514d\u6742\u6570\u636e\nmemset(buffer, 0, buf.length);<\/code><\/pre>\n\n\n\n
\u8fd9\u4e00\u6b65\u7684\u76ee\u7684\u662f\u4e3a\u4e86\u63d0\u9ad8\u6548\u7387\uff0c\u901a\u8fc7\u865a\u62df\u5185\u5b58\u6620\u5c04\u53ef\u4ee5\u76f4\u63a5\u62ff\u5230Camera\u6570\u636e\uff1b<\/p>\n\n\n\n
\u6b65\u9aa4\u516b\uff1a\u901a\u77e5Camera\u9a71\u52a8\uff0cbuffer\u5165\u5217<\/p>\n\n\n\n
ioctl(mDeviceFd, VIDIOC_QBUF, &buf)<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u4e5d\uff1a\u901a\u77e5Camera\u9a71\u52a8\uff0c\u5f00\u59cb\u63a8\u6d41<\/p>\n\n\n\n
const int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;\nioctl(mDeviceFd, VIDIOC_STREAMON, &type)<\/code><\/pre>\n\n\n\n
\u6b65\u9aa4\u5341\uff1a\u901a\u77e5Camea\u9a71\u52a8\uff0cbuffer\u51fa\u5217<\/p>\n\n\n\n
struct v4l2_buffer buf = {\n                .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,\n                .memory = V4L2_MEMORY_MMAP\n};\nioctl(mDeviceFd, VIDIOC_DQBUF, &buf);<\/code><\/pre>\n\n\n\n
\u81ea\u6b64\u6211\u4eec\u5c31\u5c06camera\u6570\u636e\u5b58\u653e\u503c\u4e86\u7c7b\u578b\u4e3av4l2_buffer\u7684buffer\u7a7a\u95f4\u5185\uff0c\u53ef\u4ee5\u8fdb\u884c\u540e\u7eed\u4f7f\u7528\u3002<\/p>\n\n\n\n
\u6b65\u9aa4\u5341\u4e00\uff1a\u505c\u6b62\u63a8\u6d41<\/p>\n\n\n\n
\u5f53\u6211\u4eec\u9700\u8981\u5173\u95edCamera\u8bbe\u5907\u6216\u8005\u4e0d\u518d\u9700\u8981Camera\u6570\u636e\u65f6\uff0c\u6211\u4eec\u9700\u8981\u505c\u6b62\u63a8\u6d41\uff1a<\/p>\n\n\n\n
const int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;\nioctl(mDeviceFd, VIDIOC_STREAMOFF, &type)<\/code><\/pre>\n\n\n\n
<\/p>\n        
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\n                    \n                        \"Happy\"\n                    <\/a>\n                    
\n                        Happy                    <\/div>\n                    
\n                                                    0<\/span>\n                        \n                                                0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n                
\n                    \n                        \"Sad\"\n                    <\/a>\n                    
\n                        Sad                    <\/div>\n                    
\n                                                    0<\/span>\n                                                                        0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n                
\n                    \n                        \"Excited\"\n                    <\/a>\n                    
\n                        Excited                    <\/div>\n                    
\n                                                    0<\/span>\n                                                                        0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n                
\n                    \n                        \"Sleepy\"\n                    <\/a>\n                    
\n                        Sleepy                    <\/div>\n                    
\n                                                    0<\/span>\n                        \n                                                0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n                
\n                    \n                        \"Angry\"\n                    <\/a>\n                    
Angry<\/div>\n                    
\n                                                    0<\/span>\n                                                                        0<\/span> %<\/span>\n                        \n                    <\/div>\n                <\/div>\n\n                
\n                    \n                        \"Surprise\"\n                    <\/a>\n                    
Surprise<\/div>\n                    
\n                                                    0<\/span>\n                                                                        0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n            <\/div>\n        <\/div>","protected":false},"excerpt":{"rendered":"
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