Dear clarius team,
i am using the solum api to capture imu data from the sensor in real-time. However, to me it is not exactly clear how to interpret the imu timestamps. I simply print the timestamps of the imu sensors readings by activating the motion data and adding a few lines to the image callback in the swift example:
// New images calblack
solum.setNewProcessedImageCallback({ (imageData: Data, imageInfo: UnsafePointer<CusProcessedImageInfo>, npos: Int32, positions: UnsafePointer<CusPosInfo>) -> Void in
// Converting the raw image data into a CGImage which can be displayed
let nfo = imageInfo.pointee
let rowBytes = nfo.width * nfo.bitsPerPixel / 8
let totalBytes = Int(nfo.height * rowBytes)
let rawBytes = UnsafeMutableRawPointer.allocate(byteCount: totalBytes, alignment: 1)
let bmpInfo = CGImageAlphaInfo.premultipliedFirst.rawValue | CGBitmapInfo.byteOrder32Little.rawValue
imageData.copyBytes(to: UnsafeMutableRawBufferPointer(start: rawBytes, count: totalBytes))
guard let colorspace = CGColorSpace(name: CGColorSpace.sRGB) else {
return
}
guard let ctxt = CGContext(data: rawBytes, width: Int(nfo.width), height: Int(nfo.height), bitsPerComponent: 8, bytesPerRow: Int(rowBytes), space: colorspace, bitmapInfo: bmpInfo) else {
return
}
self.image = ctxt.makeImage()
print("---")
for i in 0..<npos {
print(positions[Int(i)].tm)
}
})
An exemplary output for five consecutive frames looks as follows:
---
689463280470
689505028270
689546733300
689558527870
---
689505028270
689546733300
689558527870
689578225650
---
689546733300
689558527870
689578225650
689619792810
---
689578225650
689619792810
689660822410
689672663550
---
689619792810
689660822410
689672663550
689692724910
So apparently, on average 4 imu sensor readings are associated with one image frame, which would correspond to approximately 100hz (which is at the lower end of the 100-200hz i would expect reading different other issues here on github). However, several readings have the same timestamp (and same imu data), e.g. 689546733300 in the first three frames. As the imu readings should be much faster than the ultrasound imaging, i assumed an unambiguous assignment. Could you clarify this issue or point me in the direction where i misunderstood the relationship between image frames and imu sensor data?
Dear clarius team,
i am using the solum api to capture imu data from the sensor in real-time. However, to me it is not exactly clear how to interpret the imu timestamps. I simply print the timestamps of the imu sensors readings by activating the motion data and adding a few lines to the image callback in the swift example:
An exemplary output for five consecutive frames looks as follows:
So apparently, on average 4 imu sensor readings are associated with one image frame, which would correspond to approximately 100hz (which is at the lower end of the 100-200hz i would expect reading different other issues here on github). However, several readings have the same timestamp (and same imu data), e.g. 689546733300 in the first three frames. As the imu readings should be much faster than the ultrasound imaging, i assumed an unambiguous assignment. Could you clarify this issue or point me in the direction where i misunderstood the relationship between image frames and imu sensor data?