Need help getting timestamp from IMX390 camera using nvarguscamerasrc

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
#1

Hello,
I downloaded the source code of nvarguscamerasrc and I would like to get the timestamp of each frame and add it as a buffer metadata to the GstBuffer.
I understand that I need to use getSensorTimestamp() but I don’t really know where to start and where I should use this function.

Could you help me achieve this ?

  • Get the timestamp using getSensorTimestamp()
  • Adding the sensor to the GstBuffer

Thanks a lot !

#3

please refer to Topic 159220 for checking capture timestamp, Argus Timestamp, SensorTimestampTsc,

#4

Thanks for the answer.
Is there a working example of nvarguscamerasrc where getSensorTimestamp()is used ?

If not, could you give an example ?

Thanks

#5

hello user27558,

you may fetch the sensor timestamp via metadata,
here shows the brief example,

                const IEventCaptureComplete *ieventCaptureComplete
                         = interface_cast<const IEventCaptureComplete>(event);
                const CaptureMetadata *metaData = ieventCaptureComplete->getMetadata();

                if (metaData)
                {
                    const ICaptureMetadata *iCaptureMeta =
                        interface_cast<const ICaptureMetadata>(metaData);

                    printf("timestamp: %lld\n", iCaptureMeta->getSensorTimestamp());
                 }
#6

Thanks for the help,
I believe that this snippet should be used in the bool StreamConsumer::threadExecute(GstNvArgusCameraSrc *src) function. Is that right ?

#7

hello user27558,

that’s correct,
actually, you may refer to Argus/public/samples/yuvJpeg/main.cpp for printing out some capture metadata from the frame.

#8

@JerryChang

Thanks for the help,
When I try to get the ICaptureMetadata interface it fails :

Error generated. gstnvarguscamerasrc.cpp, threadExecute:631 Failed to get ICaptureMetadata interface.
Error generated. gstnvarguscamerasrc.cpp, threadFunction:247 (propagating)

And here’s the snippet of code I am using right now :
(It comes from the yuvJpeg sample)

      // --------
      // Print out some capture metadata from the frame.
      IArgusCaptureMetadata *iArgusCaptureMetadata = interface_cast<IArgusCaptureMetadata>(frame);
      if (!iArgusCaptureMetadata)
        ORIGINATE_ERROR("Failed to get IArgusCaptureMetadata interface.");

      CaptureMetadata *metadata = iArgusCaptureMetadata->getMetadata();
      ICaptureMetadata *iMetadata = interface_cast<ICaptureMetadata>(metadata);
      if (!iMetadata)
        ORIGINATE_ERROR("Failed to get ICaptureMetadata interface.");
      // --------

Any idea what could cause the error ?

I am using IMX-390 cameras and jetpack 4.6.1

Thanks !

#9

Answering my own question :

Metadata needs to be enabled in the stream settings, e.g. :

    IEGLOutputStreamSettings *iStreamSettings =
        interface_cast<IEGLOutputStreamSettings>(streamSettings);
    if (iStreamSettings)
    {
        iStreamSettings->setPixelFormat(PIXEL_FMT_YCbCr_420_888);
        iStreamSettings->setResolution(iSensorMode->getResolution());
        iStreamSettings->setMode(EGL_STREAM_MODE_FIFO);
        iStreamSettings->setMetadataEnable(true);
    }
#10

@JerryChang

What is the most reliable way to convert the timestamp given by getSensorTimestamp() to a unix timestamp ?

#11

hello user27558,

iCaptureMetadata->getSensorTimestamp() return the kernel timestamp (i.e. MONOTONIC_RAW) of sensor start-of-frame.

#12

Hello, @JerryChang

Do I need to use the following formula to get the unix timestamp ?

clock_gettime(MONOTONIC_RAW) = cycle_ns(TSC) - offset_ns

Also, what is cycle_ns(TSC) ?

#13

hello user27558,

iCaptureMetadata->getSensorTimestamp() return the kernel timestamp.
TSC it’s the HW capture timestamp, VI drivers to capture frame and store the timestamp with TSC.
please refer to Topic 159220 for the explanation.
thanks

#14

Thanks, @JerryChang for the answer, but I think I still need some help,

I use the following code to get the sensor timestamp :

      // Print out some capture metadata from the frame.
      IArgusCaptureMetadata *iArgusCaptureMetadata = interface_cast<IArgusCaptureMetadata>(frame);
      if (!iArgusCaptureMetadata) {
        ORIGINATE_ERROR("Failed to get IArgusCaptureMetadata interface.");
      }

      CaptureMetadata *metadata = iArgusCaptureMetadata->getMetadata();
      ICaptureMetadata *iMetadata = interface_cast<ICaptureMetadata>(metadata);
      if (!iMetadata) {
        ORIGINATE_ERROR("Failed to get ICaptureMetadata interface.");
      }
      unsigned long sensorTimestamp = static_cast<unsigned long>(iMetadata->getSensorTimestamp());

      CONSUMER_PRINT("\tsensorTimestamp : %lu\n",
                     sensorTimestamp
      );

And it gives me this value : 5502998961000 (in ns)

Which according to the documentation is :

Returns the kernel (SOF) timestamp for the sensor (in nanoseconds).
This is the time that the first data from this capture arrives from the sensor.

I don’t understand what cycle_ns(TSC), or offset_ns has to do with any of that. Could you give a detailed explanation ? Because the link you sent doesn’t explain that.

#15

hello user27558,

please convert the units from nanosecond to seconds, use the same unit as kernel. for example, please check the timestamp in $ dmesg.
TSC is hardware timestamp, that’s captured by RCE. don’t bother that if you’re using Argus APIs.

#16

Thanks for the answer @JerryChang

The sensor timestamp in seconds is : 8156.687446000001 which makes sense with the timestamp in dmesg.

I am using the Argus API. Do I need to calculate the adjusted SOF ? Like that ?

      struct timespec t;
      clock_gettime(CLOCK_MONOTONIC_RAW, &t);
      uint64_t monotonicRaw = (uint64_t) (t.tv_sec) * (uint64_t) 1000000000 + (uint64_t) (t.tv_nsec);
      uint64_t adjustedSof = monotonicRaw - offset_ns;

It would then allow me to calculate offset between the adjustedSof and the sensorTimestamp :

int64_t timestampOffset = static_cast<int64_t>(adjustedSof) - static_cast<int64_t>(sensorTimestamp);

Does it makes sense ?

#18

The timestamp able transfer to kernel time by (getSensorTimestamp() - offset_ns)

#20

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