In this page, I'll introduce how to get UVC camera data via v4l2. Here is my environment:<\/p>\n
We'll use Here is my uvc camera's info:<\/p>\n and let's check it's formats:<\/p>\n I'd like to get yuv data, so I choose In this page, I’ll introduce how to get UVC camera da ̷","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[54],"tags":[],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts\/896"}],"collection":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/comments?post=896"}],"version-history":[{"count":6,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts\/896\/revisions"}],"predecessor-version":[{"id":904,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts\/896\/revisions\/904"}],"wp:attachment":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/media?parent=896"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/categories?post=896"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/tags?post=896"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}v4l2-ctl<\/code> command to check camera information, here is some commands we need:<\/p>\n\n
v4l2-ctl --list-device<\/code>, list all video device.<\/li>\nv4l2-ctl --all -d \/dev\/video45<\/code>, list all information of video45.<\/li>\nv4l2-ctl --list-formats -d \/dev\/video45<\/code>, list output formats of video45.<\/li>\nv4l2-ctl --list-formats-ext -d \/dev\/video45<\/code>, list detailed information which include image size and fps.<\/li>\n<\/ol>\n[root@DCIR:\/]# v4l2-ctl --all -d \/dev\/video45\nDriver Info:\n Driver name : uvcvideo\n Card type : Rmoncam A2 1080P: RMONCAM A2 10\n Bus info : usb-ffe00000.usb-1.3\n Driver version : 4.19.193\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\nMedia Driver Info:\n Driver name : uvcvideo\n Model : Rmoncam A2 1080P: RMONCAM A2 10\n Serial : 200901010001\n Bus info : usb-ffe00000.usb-1.3\n Media version : 4.19.193\n Hardware revision: 0x00000101 (257)\n Driver version : 4.19.193\nInterface Info:\n ID : 0x03000002\n Type : V4L Video\nEntity Info:\n ID : 0x00000001 (1)\n Name : Rmoncam A2 1080P: RMONCAM A2 10\n Function : V4L2 I\/O\n Flags : default\n Pad 0x01000004 : 0: Sink\n Link 0x0200000d: from remote pad 0x1000007 of entity 'Extension 4': Data, Enabled, Immutable\nPriority: 2\nVideo input : 0 (Camera 1: ok)\nFormat Video Capture:\n Width\/Height : 1920\/1080\n Pixel Format : 'MJPG' (Motion-JPEG)\n Field : None\n Bytes per Line : 0\n Size Image : 4147200\n Colorspace : sRGB\n Transfer Function : Default (maps to sRGB)\n YCbCr\/HSV Encoding: Default (maps to ITU-R 601)\n Quantization : Default (maps to Full Range)\n Flags : \nCrop Capability Video Capture:\n Bounds : Left 0, Top 0, Width 1920, Height 1080\n Default : Left 0, Top 0, Width 1920, Height 1080\n Pixel Aspect: 1\/1\nSelection: crop_default, Left 0, Top 0, Width 1920, Height 1080, Flags: \nSelection: crop_bounds, Left 0, Top 0, Width 1920, Height 1080, Flags: \nStreaming Parameters Video Capture:\n Capabilities : timeperframe\n Frames per second: 30.000 (30\/1)\n Read buffers : 0\n brightness 0x00980900 (int) : min=-64 max=64 step=1 default=0 value=0\n contrast 0x00980901 (int) : min=0 max=100 step=1 default=32 value=32\n saturation 0x00980902 (int) : min=0 max=100 step=1 default=64 value=64\n hue 0x00980903 (int) : min=-180 max=180 step=1 default=0 value=0\n white_balance_temperature_auto 0x0098090c (bool) : default=1 value=1\n gamma 0x00980910 (int) : min=100 max=500 step=1 default=300 value=300\n gain 0x00980913 (int) : min=1 max=128 step=1 default=64 value=64\n power_line_frequency 0x00980918 (menu) : min=0 max=2 default=1 value=1\n white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=10 default=4600 value=4600 flags=inactive\n sharpness 0x0098091b (int) : min=0 max=100 step=1 default=50 value=50\n backlight_compensation 0x0098091c (int) : min=0 max=2 step=1 default=0 value=0\n exposure_auto 0x009a0901 (menu) : min=0 max=3 default=3 value=3\n exposure_absolute 0x009a0902 (int) : min=50 max=10000 step=1 default=166 value=166 flags=inactive\n exposure_auto_priority 0x009a0903 (bool) : default=0 value=1<\/code><\/pre>\n[root@DCIR:\/]# v4l2-ctl --list-formats -d \/dev\/video45\nioctl: VIDIOC_ENUM_FMT\n Type: Video Capture\n\n [0]: 'MJPG' (Motion-JPEG, compressed)\n [1]: 'YUYV' (YUYV 4:2:2)\n[root@DCIR:\/]# v4l2-ctl --list-formats-ext -d \/dev\/video45\nioctl: VIDIOC_ENUM_FMT\n Type: Video Capture\n\n [0]: 'MJPG' (Motion-JPEG, compressed)\n Size: Discrete 1920x1080\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 160x120\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 320x240\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 320x180\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 640x480\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 800x600\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 848x480\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 960x540\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 1280x720\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 1280x1024\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 640x360\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 176x144\n Interval: Discrete 0.033s (30.000 fps)\n [1]: 'YUYV' (YUYV 4:2:2)\n Size: Discrete 1920x1080\n Interval: Discrete 0.200s (5.000 fps)\n Size: Discrete 160x120\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 320x240\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 320x180\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 640x480\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 800x600\n Interval: Discrete 0.050s (20.000 fps)\n Size: Discrete 848x480\n Interval: Discrete 0.050s (20.000 fps)\n Size: Discrete 960x540\n Interval: Discrete 0.050s (20.000 fps)\n Size: Discrete 1280x720\n Interval: Discrete 0.100s (10.000 fps)\n Size: Discrete 1280x1024\n Interval: Discrete 0.100s (10.000 fps)\n Size: Discrete 640x360\n Interval: Discrete 0.033s (30.000 fps)\n Size: Discrete 176x144\n Interval: Discrete 0.033s (30.000 fps)<\/code><\/pre>\n\u00a72 Example Code<\/h2>\n
2.1 extern define<\/h3>\n
V4L2_PIX_FMT_YUYV<\/code> as my pix format. Usually, UVC camera is single-planar capture, so our buffer type is V4L2_BUF_TYPE_VIDEO_CAPTURE<\/code>, but some MIPI-CSI, DVP and CIF camera maybe multi-planar device, and it's parsing method is different from single-planar device. The method of getting multi-planar camera data will be introduce in subsequent chapters. At the same time, we specify the query buffer number equals 5.<\/p>\n\/* =================== *\/\n\/* ===== .h file ===== *\/\n\/* =================== *\/\n\n#define _Video_Device_SP_ "\/dev\/video45"\n#define _V4L2_SP_PIX_FMT_ V4L2_PIX_FMT_YUYV\n#define _V4L2_SP_BUF_TYPE_ V4L2_BUF_TYPE_VIDEO_CAPTURE\n#define _V4L2_SP_BUF_REQ_COUNT_ 5\n\nextern const int v4l2_sp_capture_width;\nextern const int v4l2_sp_capture_height;\n\n\/\/ device number for v4l2 single-planar\nextern int v4l2_sp_fd;\n\n\/\/ global memory for mmap v4l2 query buffer, 5 block\nextern uint8_t* v4l2_sp_globalBuffer[_V4L2_SP_BUF_REQ_COUNT_];\n\n\/\/ global memory buffer length\nextern int v4l2_sp_globalBufferLength;\n\n\/\/ to specify which memory is currently available\nextern int v4l2_sp_globalBufferIndex;\n\n\/\/ to specify globalBuffer length\nextern int v4l2_sp_globalBufferLength;\n\n\/\/ stop capture or not\nextern bool v4l2_sp_captureLoopFlag;\n\n\/* =================== *\/\n\/* ===== .c file ===== *\/\n\/* =================== *\/\n\nconst int v4l2_sp_capture_width = 640;\nconst int v4l2_sp_capture_height = 480;\n\nint v4l2_sp_fd;\nuint8_t* v4l2_sp_globalBuffer[_V4L2_SP_BUF_REQ_COUNT_];\nint v4l2_sp_globalBufferLength;\nint v4l2_sp_globalBufferIndex;\n\nbool v4l2_sp_captureLoopFlag = true;<\/code><\/pre>\n2.1 implement<\/h3>\n
int V4L2_SP_Streaming()\n{\n \/* Step 0 : Pre-Define *\/\n int retval = 0; \/\/ V4L2_SP_Streaming return value\n int ret = 0; \/\/ ioctl check\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 1 Open Device\\n");\n#endif\n \/* Step 1 : Open Device *\/\n v4l2_sp_fd = open(_Video_Device_SP_, O_RDWR);\n if (v4l2_sp_fd == -1)\n {\n perror("V4L2_SP_Streaming() open device");\n retval = 1;\n goto out_return;\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 2 Setting Capture Format\\n");\n#endif\n \/* Step 2: Setting Capture Format *\/\n struct v4l2_format format;\n format.type = _V4L2_SP_BUF_TYPE_;\n format.fmt.pix.width = v4l2_sp_capture_width;\n format.fmt.pix.height = v4l2_sp_capture_height;\n format.fmt.pix.pixelformat = _V4L2_SP_PIX_FMT_;\n\n ret = ioctl(v4l2_sp_fd, VIDIOC_S_FMT, &format); \/\/ set FMT\n if (ret == -1)\n {\n perror("V4L2_SP_Streaming() setting format");\n retval = 2;\n goto error_close;\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 3 Checking FMT Setting\\n");\n#endif\n \/* Step 3: Checking FMT Setting *\/\n ret = ioctl(v4l2_sp_fd, VIDIOC_G_FMT, &format); \/\/ get FMT\n if (ret == -1)\n {\n perror("V4L2_SP_Streaming() checking format");\n retval = 3;\n goto error_close;\n }\n\n if (format.fmt.pix.pixelformat == _V4L2_SP_PIX_FMT_) \/\/ set FMT == get FMT ?\n {\n printf("ioctl VIDIOC_S_FMT sucessful\\n");\n }\n else\n {\n printf("ioctl VIDIOC_S_FMT failed\\n");\n retval = 4;\n goto error_close;\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 4 Request Buffer\\n");\n#endif\n \/* Step 4: Request Buffer *\/\n struct v4l2_requestbuffers reqbuf;\n reqbuf.count = _V4L2_SP_BUF_REQ_COUNT_;\n reqbuf.type = _V4L2_SP_BUF_TYPE_;\n reqbuf.memory = V4L2_MEMORY_MMAP;\n ret = ioctl(v4l2_sp_fd, VIDIOC_REQBUFS, &reqbuf);\n if (-1 == ret)\n {\n perror("V4L2_SP_Streaming() reqeuset buff");\n retval = 1;\n goto error_close;\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 5 mmap Buffer\\n");\n#endif\n \/* Step 5: mmap Buffer *\/\n struct v4l2_buffer buff;\n buff.type = _V4L2_SP_BUF_TYPE_;\n buff.memory = V4L2_MEMORY_MMAP;\n for (int i = 0; i < _V4L2_SP_BUF_REQ_COUNT_; ++i)\n {\n \/\/ query buf\n buff.index = i;\n ret = ioctl(v4l2_sp_fd, VIDIOC_QUERYBUF, &buff);\n if (ret == -1)\n {\n perror("V4L2_SP_Streaming() query");\n retval = 2;\n goto error_close;\n }\n\n printf("buf[%d]: len = %d offset: %d\\n", i, buff.length, buff.m.offset);\n\n \/\/ mmap\n v4l2_sp_globalBuffer[i] = mmap(NULL, buff.length, PROT_READ, MAP_SHARED, v4l2_sp_fd, buff.m.offset);\n v4l2_sp_globalBufferLength = buff.length;\n if (MAP_FAILED == v4l2_sp_globalBuffer[i])\n {\n perror("V4L2_SP_Streaming() mmap");\n retval = 3;\n goto error_munmap;\n }\n\n \/\/ queue\n ret = ioctl(v4l2_sp_fd, VIDIOC_QBUF, &buff);\n if (-1 == ret)\n {\n perror("V4L2_SP_Streaming() queue");\n retval = 4;\n goto error_munmap;\n }\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 6 Start Streaming\\n");\n#endif\n \/* Step 6: Start Streaming *\/\n int on = _V4L2_SP_BUF_TYPE_;\n ret = ioctl(v4l2_sp_fd, VIDIOC_STREAMON, &on);\n if (-1 == ret)\n {\n perror("V4L2_SP_Streaming() VIDIOC_STREAMON");\n retval = 5;\n goto error_munmap;\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Step 7 Capture\\n");\n#endif\n \/* Step 7: Capture *\/\n while (v4l2_sp_captureLoopFlag)\n {\n \/\/ deque\n ret = ioctl(v4l2_sp_fd, VIDIOC_DQBUF, &buff);\n if (ret != -1)\n {\n \/\/ updata global var\n v4l2_sp_globalBufferIndex = buff.index;\n v4l2_sp_globalBufferLength = buff.bytesused;\n\n \/\/ queue\n ret = ioctl(v4l2_sp_fd, VIDIOC_QBUF, &buff);\n }\n }\n\n#if Print_Debug_Info\n printf("V4L2_SP_Streaming(): Exit\\n");\n#endif\nerror_munmap:\n for (int i = 0; i < _V4L2_SP_BUF_REQ_COUNT_; ++i)\n {\n if (v4l2_sp_globalBuffer[i] != NULL)\n munmap(v4l2_sp_globalBuffer[i], v4l2_sp_globalBufferLength);\n }\n\nerror_close:\n close(v4l2_sp_fd);\n\nout_return:\n return retval;\n}<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"