Azure Kinect 获取相机内参
处理 Kinect 相机录制的深度视频时，有时候需要用到相机内参，发现网上不太有相关资源，故总结一下。
录制 mkv 文件中获取
录制得到 mkv 文件中存在附件 calibration.json，存储了相机的内外参数。
点击查看附件具体内容
{
"CalibrationInformation": {
"Cameras": [
{
"Intrinsics": {
"ModelParameterCount": 14,
"ModelParameters": [
0.49862006306648254,
0.49299359321594238,
0.49295613169670105,
0.49312511086463928,
3.8691997528076172,
2.0663304328918457,
0.086164794862270355,
4.2011380195617676,
3.3314094543457031,
0.50915241241455078,
0,
0,
7.02285033185035E-5,
0.00015635808813385665
],
"ModelType": "CALIBRATION_LensDistortionModelBrownConrady"
},
"Location": "CALIBRATION_CameraLocationD0",
"Purpose": "CALIBRATION_CameraPurposeDepth",
"MetricRadius": 1.7399997711181641,
"Rt": {
"Rotation": [
1,
0,
0,
0,
1,
0,
0,
0,
1
],
"Translation": [
0,
0,
0
]
},
"SensorHeight": 1024,
"SensorWidth": 1024,
"Shutter": "CALIBRATION_ShutterTypeUndefined",
"ThermalAdjustmentParams": {
"Params": [
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0
]
}
},
{
"Intrinsics": {
"ModelParameterCount": 14,
"ModelParameters": [
0.50041943788528442,
0.51068669557571411,
0.476089745759964,
0.63471859693527222,
0.34417539834976196,
-2.8604564666748047,
1.8035205602645874,
0.21697279810905457,
-2.6490097045898437,
1.7056518793106079,
0,
0,
-4.4145919673610479E-5,
0.00047436624299734831
],
"ModelType": "CALIBRATION_LensDistortionModelBrownConrady"
},
"Location": "CALIBRATION_CameraLocationPV0",
"Purpose": "CALIBRATION_CameraPurposePhotoVideo",
"MetricRadius": 0,
"Rt": {
"Rotation": [
0.99997377395629883,
0.0072122937999665737,
-0.00064296292839571834,
-0.007122507318854332,
0.99573004245758057,
0.092037834227085114,
0.0013040214544162154,
-0.0920308455824852,
0.99575531482696533
],
"Translation": [
-0.032023865729570389,
-0.0021201763302087784,
0.0039135357365012169
]
},
"SensorHeight": 3072,
"SensorWidth": 4096,
"Shutter": "CALIBRATION_ShutterTypeUndefined",
"ThermalAdjustmentParams": {
"Params": [
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0
]
}
}
],
"InertialSensors": [
{
"BiasTemperatureModel": [
-0.016476714983582497,
0,
0,
0,
0.024192806333303452,
0,
0,
0,
0.015445239841938019,
0,
0,
0
],
"BiasUncertainty": [
9.9999997473787516E-5,
9.9999997473787516E-5,
9.9999997473787516E-5
],
"Id": "CALIBRATION_InertialSensorId_LSM6DSM",
"MixingMatrixTemperatureModel": [
0.98985481262207031,
0,
0,
0,
-0.0027861578855663538,
0,
0,
0,
-0.0029240367002785206,
0,
0,
0,
-0.0027407032903283834,
0,
0,
0,
1.0062906742095947,
0,
0,
0,
-0.0052220304496586323,
0,
0,
0,
-0.0029174494557082653,
0,
0,
0,
-0.0052966782823204994,
0,
0,
0,
0.99210965633392334,
0,
0,
0
],
"ModelTypeMask": 16,
"Noise": [
0.00095000001601874828,
0.00095000001601874828,
0.00095000001601874828,
0,
0,
0
],
"Rt": {
"Rotation": [
-0.0037576679605990648,
0.11113974452018738,
-0.9937976598739624,
-0.99998712539672852,
-0.0038041053339838982,
0.0033556451089680195,
-0.0034075656440109015,
0.99379748106002808,
0.11115261167287827
],
"Translation": [
0,
0,
0
]
},
"SecondOrderScaling": [
0,
0,
0,
0,
0,
0,
0,
0,
0
],
"SensorType": "CALIBRATION_InertialSensorType_Gyro",
"TemperatureBounds": [
5,
60
],
"TemperatureC": 0
},
{
"BiasTemperatureModel": [
-0.0095243612304329872,
0,
0,
0,
-0.0029438617639243603,
0,
0,
0,
-0.11047996580600739,
0,
0,
0
],
"BiasUncertainty": [
0.0099999997764825821,
0.0099999997764825821,
0.0099999997764825821
],
"Id": "CALIBRATION_InertialSensorId_LSM6DSM",
"MixingMatrixTemperatureModel": [
1.0036085844039917,
0,
0,
0,
-0.000692621513735503,
0,
0,
0,
-0.0016570064472034574,
0,
0,
0,
-0.00070016534300521016,
0,
0,
0,
0.99279278516769409,
0,
0,
0,
0.0003493333060760051,
0,
0,
0,
-0.0016633484046906233,
0,
0,
0,
0.00034689210588112473,
0,
0,
0,
0.99978172779083252,
0,
0,
0
],
"ModelTypeMask": 56,
"Noise": [
0.010700000450015068,
0.010700000450015068,
0.010700000450015068,
0,
0,
0
],
"Rt": {
"Rotation": [
-0.0040588844567537308,
0.10675475746393204,
-0.99427711963653564,
-0.99998855590820313,
-0.0029550541657954454,
0.0037649183068424463,
-0.0025362195447087288,
0.994280993938446,
0.10676553100347519
],
"Translation": [
-0.050834301859140396,
0.00404530530795455,
0.00093045207904651761
]
},
"SecondOrderScaling": [
0,
0,
0,
0,
0,
0,
0,
0,
0
],
"SensorType": "CALIBRATION_InertialSensorType_Accelerometer",
"TemperatureBounds": [
5,
60
],
"TemperatureC": 0
}
],
"Metadata": {
"SerialId": "000266714512",
"FactoryCalDate": "11/2/2021 9:10:55 AM GMT",
"Version": {
"Major": 1,
"Minor": 2
},
"DeviceName": "AzureKinect-PV",
"Notes": "PV0_max_radius_invalid"
}
}
}
不过看起来，这里使用的相机模型是 BrownConrady，有 14 个参数，我并不太了解含义……
官方 sdk 获取相机内参
这里 提到官方 SDK 提供了输出 calibration 的接口：Azure-Kinect-Sensor-SDK/examples/calibration/main.cpp at develop · microsoft/Azure-Kinect-Sensor-SDK。
具体可看代码，通过 calib.intrinsics.parameters.param 获取。
第三方工具
pykinect 是基于官方 API 封装的 python 模块，也可以实现获取相机内参。假设我们录制得到了 kinect.mkv 视频，从视频中读取各项参数的代码如下：
import pykinect_azure as pykinect
pykinect.initialize_libraries()
playback = pykinect.start_playback(r"data\kinect.mkv")
calibration = playback.get_calibration()
# see: https://github.com/microsoft/Azure-Kinect-Sensor-SDK/blob/develop/examples/calibration/main.cpp#L79-L80
resolution_width = calibration._handle.depth_camera_calibration.resolution_width
resolution_height = calibration._handle.depth_camera_calibration.resolution_height
depth_params = calibration.depth_params
message = (
"Depth Intrinsic parameters: \n"
f"\tcx: {depth_params.cx}\n"
f"\tcy: {depth_params.cy}\n"
f"\tfx: {depth_params.fx}\n"
f"\tfy: {depth_params.fy}\n"
f"\tk1: {depth_params.k1}\n"
f"\tk2: {depth_params.k2}\n"
f"\tk3: {depth_params.k3}\n"
f"\tk4: {depth_params.k4}\n"
f"\tk5: {depth_params.k5}\n"
f"\tk6: {depth_params.k6}\n"
f"\tcodx: {depth_params.codx}\n"
f"\tcody: {depth_params.cody}\n"
f"\tp2: {depth_params.p2}\n"
f"\tp1: {depth_params.p1}\n"
f"\tmetric_radius: {depth_params.metric_radius}\n"
)
print(message)
也许可以获得更多参数，但是要翻翻官方 API 文档才能知道了。
另外，我发现 open3d 也内置了 kinect 的相机参数：open3d.camera.PinholeCameraIntrinsicParameters - Open3D 0.18.0 documentation，不过看起来只支持了 Kinect2。
