Best Way to Receive / Store Image Data using COSMOS v4

[charlie-norgaard]

Hey all,

I need a way to receive raw image data from a remote camera using COSMOS v4. The camera will send 100kB of raw image data and I need a way to 'catch' and store this data using COSMOS. We have a python program for decompressing the data and converting it into a viewable image format, so I really just need the raw data so I can store and export it to another file that our python program can read in.

I got in contact with one of the COSMOS devs a while back about this same question and they said they created a Qt application that "gets raw image data from COSMOS, writes to a file, and then uses a Qt::Image and Qt::Pixmap.fromImage to set a Qt::Label.pixmap to the image".

I have no experience in Qt app development and am wondering if there is just a simple way to define the image as a telemetry item in our tlm.txt file. Does anyone have any suggestions as to how I might go about defining the image as a telemetry item? Would the data type = BLOCK and size = 800000 (bits)?

Any ideas/recommendations would be much appreciated!

[ghost]

Yes you want a BLOCK telemetry ITEM. Note you can have a variable length item if you need but you can only have 1 per packet. That item is designated with a length of 0. TlmExtractor should be able to extract the data but it will try to put it into a text file which probably won't work. You may need to implement your own subclass of PacketLogReader and write the data directly to a binary file.

[charlie-norgaard]

Great! Thanks for clarifying that for me. Could you possibly direct me to the documentation for writing/implementing my own subclass in COSMOS? The link you put under PacketLogReader just redirects me to ITEM in the telemetry file documentation. Thanks again.

[ghost]

Sorry I fixed the link in my reply. You'll have to subclass PacketLogReader something like this (setup to read the BLOCKTEST field in our demo):

require 'cosmos'
require 'cosmos/packet_logs/packet_log_reader'
class MyReader < Cosmos::PacketLogReader
  def process(filename)
    File.open('out.bin', 'wb') do |file|
      each(filename) do |packet|
        if packet.target_name == 'INST' && packet.packet_name == 'HEALTH_STATUS'
          file.write(packet.read('BLOCKTEST', :RAW))
        end
      end
    end
  end
end

reader = MyReader.new
reader.process(ARGV[0])

Run from inside the demo directory like: bundle exec ruby my_reader.rb outputs\logs\2020_06_25_14_35_55_tlm.bin

[charlie-norgaard]

Very helpful! Thank you!