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Re: [Discuss-gnuradio] Bug with scrambler in hierarchical block

From: Daniel Estévez
Subject: Re: [Discuss-gnuradio] Bug with scrambler in hierarchical block
Date: Tue, 14 Feb 2017 21:58:22 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0

El 14/02/17 a las 19:15, Bastian Bloessl escribió:

> I tested the flow graph with current next and master branches and didn't
> see the problem, i.e., the first byte of both message debug blocks was
> always 0xff.
> Are you sure you don't use any custom patches?

I only have the Viterbi decoder patched.

This problem also happens to other people. I found the bug originally in
my AO-73 decoder in gr-satellites:


The CCSDS descramble will descramble incorrectly the 1st bit in the
packet (except for the first packet) and you'll always end up with 1
error in the Reed-Solomon decoder. Other users have also told me about
this problem.

Testing this is more elaborate than with the simple flowgraph I sent
before. In case anyone wants to try, the sample recordings at


can be used together with the audio streamer in gr-frontends.

Regarding the simple flowgraph I sent before, I think this problem is
not so easy to reproduce. It probably depends on what version you're
running and all sorts of things. I changed the name of the "packet_len"
tags in the CCSDS scrambler and the problem disappeared in my simple
flowgraph but not in the AO-73 decoder from gr-satellites.

I'm afraid I can't be of much more help right now. If I notice anything
new I'll write again.



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