json11 in nx_kit does not seem to parse json string properly

Answered

Permanently deleted user

August 08, 2021 18:41 Edited

I add the following snippet to device_agent.cpp to simulate retrieving polygon coordinates (aka. points):

std::string pf_err;
std::string test = R"({"figure":{"color":"#e040fb","points":[[0.795,0.7058823529411765],[0.785,0.9558823529411765],[0.9483333333333334,0.961764705882353],[0.97,0.7294117647058823]]},"label":"aaa","showOnCamera":true})";
printf(">>>> test: %s\n", test.c_str());
Json js_polygon = Json::parse(test, pf_err);
std::cout << ">>>> js_polygon = " << js_polygon.dump() << "\n";

the parsed result is not identical to the content of "test", this is what I got:

>>>> js_polygon = {"figure": {"color": "#e040fb", "points": [[null, null], [null, null], [null, null], [null, null]]}, "label": "aaa", "showOnCamera": true}

those numbers of coordinates (aka. points) become "null" after the json string is parsed.

Please correct me if I am not using json11 in the right way.

 

 

 

 

 

 

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• 

  Permanently deleted user

  August 09, 2021 02:18

  When I change points to string array, Json::parse() is able to parse properly.

  std::string pf_err;
  std::string test = R"({"figure":{"color":"#e040fb","points":[["0.795","0.7058823529411765"],["0.785","0.9558823529411765"],["0.9483333333333334","0.961764705882353"],["0.97","0.7294117647058823"]]},"label":"aaa","showOnCamera":true})";
  printf(">>>> test: %s\n", test.c_str());
  Json js_polygon = Json::parse(test, pf_err);
  std::cout << ">>>> js_polygon = " << js_polygon.dump() << "\n";

  and the output becomes

  >>>> js_polygon = {"figure": {"color": "#e040fb", "points": [["0.795", "0.7058823529411765"], ["0.785", "0.9558823529411765"], ["0.9483333333333334", "0.961764705882353"], ["0.97", "0.7294117647058823"]]}, "label": "aaa", "showOnCamera": true}

  However, the polygon setting retrieved by "settingValue()" has points as double array.

  How do I configure json11 to make it parse double array properly?

   

   

   

   

   

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• 

  Permanently deleted user

  August 09, 2021 05:54

  after updating strtod_dot() in json11.cpp, I am able to get those double values

  double strtod_dot(const char* str) {
  const size_t str_length = strspn(str, "0123456789.eE+-");
  
  char str_double[str_length+1] = {0};
  strncpy(str_double, str, str_length);
  double f = atof(str_double);
  return f;
  }

   

   

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• 

  Andrey Terentyev

  • Network Optix team

  September 07, 2021 16:04

  Hello James,

  I took the sample_analytics_plugin of the Metadata SDK.

  I refactored your code a little and put it into the DeviceAgent::pushUncompressedVideoFrame() method.
  You can use any other method of your choice.

  Include the <nx/kit/json.h> header file.

  Here is the code

      std::string pf_err;
      std::string test = R"({
          "figure":{ 
              "color":"#e040fb",
              "points":[
                  [0.795,0.7058823529411765],
                  [0.785,0.9558823529411765],
                  [0.9483333333333334,0.961764705882353],
                  [0.97,0.7294117647058823]
              ]
          },
          "label":"aaa",
          "showOnCamera":true})";
      NX_PRINT << ">>>> test: " << test;
      nx::kit::Json js_polygon = nx::kit::Json::parse(test, pf_err);
      NX_PRINT << ">>>> js_polygon = " << js_polygon.dump();

  And here is the output. The code seems working correctly.

  

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• 

  Permanently deleted user

  September 20, 2021 13:36

  Hi Andrey,

  I am experiencing something very strange. I tried to create a Json object with a double value, but the created Json object does not have the value. When I do the same thing with an integer, the created Json has the value. What happens?

  

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• 

  Andrey Terentyev

  • Network Optix team

  February 28, 2022 17:19

  Hello James,

  Here is what I did to test that.

  1. I took Nx Meta and Metadata SDK 5.0.0.34326

  2. Refactored sample_analytics_plugin

  bool DeviceAgent::pullMetadataPackets(std::vector<IMetadataPacket*>* metadataPackets)
  {
      nx::kit::Json jsonDouble =  nx::kit::Json((double) 0.71111);
      NX_PRINT << "DEBUG " << jsonDouble.dump();
      metadataPackets->push_back(generateObjectMetadataPacket().releasePtr());
      
      return true; //< There were no errors while filling metadataPackets.
  }

  3. Rebuilt the plugin.

  4. Copied the plugin to the "plugins" folder

  5. Configured Server output redirection

  sudo touch /home/networkoptix-metavms/.config/nx_ini/mediaserver_stderr.log

  6. Restarted the Server.

  7. Logged in via GUI and enabled Sample plugin on a camera.

  8. Monitored the /home/networkoptix-metavms/.config/nx_ini/mediaserver_stderr.log file

  sudo tail -f /home/networkoptix-metavms/.config/nx_ini/mediaserver_stderr.log | grep DEBUG

  Here is the result

  

  Seems everything works fine.

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