Argus CaptureMetadata getFrameReadoutTime() is more than 1 / FPS

Robotics & Edge Computing Jetson & Embedded Systems Jetson Orin NX
1

I have jetson orin nx with JP6.1 and imx577 camera. I need to get timestamp for every row of image. To calculate the time of first row i fix time right after frameConsumer->acquireFrame()
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
uint64_t curTimeNs = static_cast<uint64_t>(ts.tv_sec) * BILLION + static_cast<uint64_t>(ts.tv_nsec);
and
firstRowLatency = iFrame->getTime() - iCaptureMetadata->getSensorTimestamp() + iCaptureMetadata->getSensorExposureTime()
firstRowTimestamp = curTimeNs - firstRowLatency
To calculate other rows timestamps i need to know readoutTime
ith_rowTimestamp = firstRowTimestamp + i * readoutTime / height
but i got iCaptureMetadata->getFrameReadoutTime() ~ 125ms, which is impossible, because FPS is 21, so readout time can’t be more than 1000 / 21 ms ~ 47.6 ms
Am i doing something wrong or iCaptureMetadata->getFrameReadoutTime() working wrong ?

3

The readouttime is calculate by below.

active_pixel_height * line_length/pix_clk_hz

4

I know that , but i don’t know where to get ‘pix_clk_hz’.

5

It’s reported by device tree.

6

I could not find ‘pix_clk_hz’ and i think iCaptureMetadata->getFrameReadoutTime() returns wrong value.
But I did rolling shutter calibration for imx577 and calc time difference between first and last lines of the image:
for sensor mode0 4032x3040 21fps I got ~44ms,
for sensor mode1 3840x2160 30fps I got ~ 29ms,
for sensor mode2 1920x1080 60fps I got ~ 9ms
It looks like this values are the same as
‘iSensorTimestampTsc->getSensorEofTimestampTsc() - iSensorTimestampTsc->getSensorSofTimestampTsc()’

7

pix_clk_hz is report by sensor driver device tree.

8

One more time
for sensor mode0 4032x3040 21fps ‘iCaptureMetadata->getFrameReadoutTime() ~125ms’
But if readoutTime is 125ms, than fps cant be more than 1000 / 125 = 8.
Which means that ‘iCaptureMetadata->getFrameReadoutTime()’ returns wrong value, or it is not readoutTime.

9

As my previous comment the readout time doesn’t matter with the frame rate.

11

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