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Re: [Discuss-gnuradio] gr-ais: bit unstuffing bug?
From: |
Christian Gagneraud |
Subject: |
Re: [Discuss-gnuradio] gr-ais: bit unstuffing bug? |
Date: |
Fri, 10 Aug 2012 20:30:31 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:14.0) Gecko/20120713 Thunderbird/14.0 |
On 10/08/12 19:55, Nick Foster wrote:
You can do it either way since unstuffing will never generate a valid
HDLC framing code ("01111110"). Unstuffing before the deframing
For what i understand, bit stuffing never generates framing code (that's
the whole point), but the bit *un*stuffing can and will if the payload
contains itself a byte which as the same value as the framing code.
Actually, while dumping data from ais_parse.cc, I found that gr-ais
unstuffing code do generate framing codes. that has fooled
get_tags_in_range (a stop was found because the AIS payload had a
01111110 in it).
Well, I think I found, I'm still scratching my head....
correlators means my tags' sample numbers don't have to be modified for
the bits inserted by the unstuffing operation.
Yes, I see the point. But you could unstuff inline, in place of the
memcpy, just before calling parse().
Chris
--n
On Fri, Aug 10, 2012 at 11:47 AM, Christian Gagneraud
<address@hidden <mailto:address@hidden>> wrote:
Hi all, Nick,
In gr-ais. the bit un-stuffing is done before the de-framing,
shouldn't it be done after instead?
Chris
--
Christian Gagneraud,
Embedded systems engineer.
Techworks Marine
1 Harbour road
Dun Laoghaire
Co. Dublin
Ireland
Tel: + 353 (0) 1 236 5990 <tel:%2B%20353%20%280%29%201%20236%205990>
Web: http://www.techworks.ie/
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--
Christian Gagneraud,
Embedded systems engineer.
Techworks Marine
1 Harbour road
Dun Laoghaire
Co. Dublin
Ireland
Tel: + 353 (0) 1 236 5990
Web: http://www.techworks.ie/