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Issue with ASTERIX category 48 packets (and ASTERIX Final format) #241

@desaintmoulin

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@desaintmoulin

Hello,

I face an issue while using asterix-decoder to decode ASTERIX category 48 data from an ASTERIX Final format file. Here are the details of the problem:

  • Initial raw data = b'\x000\x00\x00\x00\x01N\x9e0\x00$\xf3\x1f\x01\x02\x06G\x01\xab\xb7@w1\xdcr`\x02\xc6\x03<\xd2Z&N\x07\xf4]g\xc6\x05@\x08\x80@\xa5\xa5\xa5\xa5' <=> 00 30 00 00 00 01 4E 9E 30 00 24 F3 1F 01 02 06 47 01 AB B7 40 77 31 DC 72 60 02 C6 03 3C D2 5A 26 4E 07 F4 5D 67 C6 05 40 08 80 40 A5 A5 A5 A5

  • Data retrieved between header and footer of ASTERIX final format: b'0\x00$\xf3\x1f\x01\x02\x06G\x01\xab\xb7@w1\xdcr`\x02\xc6\x03<\xd2Z&N\x07\xf4]g\xc6\x05@\x08\x80@' <=> 30 00 24 F3 1F 01 02 06 47 01 AB B7 40 77 31 DC 72 60 02 C6 03 3C D2 5A 26 4E 07 F4 5D 67 C6 05 40 08 80 40

Manually, from this block, we can extract
category = 30 => 48
length = 00 24 => 36 bytes => only one ASTERIX packet
FSPEC = F3 1F 01 02 => 11110011 00011111 00000001 00000010
SAC/SIC = 06 47 => 06/71 (military equipment in Belgium)
...
Thus, the packet seems valid. When using asterix.parse on the data without the header and footer, I obtain

asterix.parse(b'0\x00$\xf3\x1f\x01\x02\x06G\x01\xab\xb7@w1\xdcr`\x02\xc6\x03<\xd2Z&N\x07\xf4]g\xc6\x05@\x08\x80@') =>[{'category': 48, 'len': 28, 'crc': '00000000', 'ts': 1758724455669.0, 'hexdata': None}, {'category': 48, 'len': 4, 'crc': '00000000', 'ts': 1758724455669.0, 'hexdata': None}, {'category': 48, 'len': 1, 'crc': '00000000', 'ts': 1758724455669.0, 'hexdata': None}]

One can notice that the parser returns multiple ASTERIX packets with wrong length and no hexdata, instead of one ASTERIX packet with data. I have no idea why there is an issue for this frame, it works well with other frames... Do you have any idea?

Thank you,

Best regards,

François De Saint Moulin

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