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Re: [Discuss-gnuradio] Intercommunicate processes

From: Pol Henarejos
Subject: Re: [Discuss-gnuradio] Intercommunicate processes
Date: Wed, 01 Aug 2012 09:19:04 +0200
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Dear Tom,

Even though the loses are low, I would like to do not lose any sample. I
implemented a sink/source block using shared memory and I can guarantee
that there are no loses.
However I discovered a deeper problem. There is a strange behaviour with
hier_block2. I test the following topoly:
A -> B -> C -> D, where B and C are sink/source blocks (using shared
memory or udp, it does not matter, they are basic blocks). A and D are a
CRC encoder and decoder but in a hier_block2. In more detail, in A there
are the following connections:
Data_Generator -> CRC_attacher -> self
D is the reciprocal block. CRC_attacher is also a hier_block2 in the
following way:
self -> CRC_compute -> self

Hence, I use a hier_block2 inside another one. Yes, I know I could use
CRC_compute without being encapsulated in the hier_block2 but in the
future will be additional blocks.
With this topology there are CRC fails. If I use CRC_compute without
hier_block2 all CRC decodings are ok. So it seems there is a rare
problem with hier_block2.
I read a similar problem in
and therefore I put a kludge_copy after/before self connections. But the
problem still occurs.

What could it be?


Pol Henarejos
Research Engineer, MSc

Centre Tecnol├▓gic de Telecomunicacions de Catalunya (CTTC)
Engineering Unit
Parc Mediterrani de la Tecnologia
Av. Carl Friedrich Gauss, 7
08860 Castelldefels, Barcelona (Spain)
Tel: +34 93 396 71 70  Ext: 2177
Fax. +34 93 645 29 01

El 30/07/2012 13:44, Tom Rondeau escribi├│:
> On Mon, Jul 30, 2012 at 4:33 AM, Pol Henarejos <address@hidden> wrote:
>> Dear list,
>> I would need to communicate two separated gnuradio programs. I tried to
>> use udp_sink / udp_source in the same machine but there are many many
>> packets lost. Is there a way to use a kind of sink/source without losses
>> to communicate separated programs in Windows?
>> I also tried to use a tcp stack to obtain a fileno and then use
>> file_descriptor_source/sink but in windows is not possible to use
>> read/write on a socket descriptor (you can only use recv/send). So I
>> need to find another solution but I don't know how to solve it.
>> Thanks for your help.
>> --
>> Pol Henarejos
> Pol,
> What kind of packet losses are you seeing? It shouldn't be that high,
> but UDP gives you no guarantee that packets won't be dropped or even
> show up in order. Still, for loopback, I would expect less than 1%
> packet loss rate (I think that I'm being overly pessimistic, but I've
> heard reports for more), so I'm more just curious what kind of
> performance you're seeing on Windows.
> You could try to recreate the UDP source/sink as TCP, instead. But if
> you have the same kinds of losses, just know that with the
> retransmissions, you're going to have to slow things down.
> If you were on Linux, I'd suggest using FIFOs on a RAM disk, but I'm
> not sure you can do that in Windows.
> Tom

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