Re: [Discuss-gnuradio] What do Packet Encoder and Packet Decoder do?

[Martin Braun]

Hm, interesting. You know, in this specific configuration, you don't
need a throttle. What happens if you leave it out? It shouldn't change
anything, but then, it should work in any case.

Also, you *are* letting the fg terminate itself, right?

M

On 07/31/2014 04:30 AM, Nguyễn Văn Lý wrote:
> Hi Martin,
> 
> Consider the following flow graph.
> File Source ------->Throttle --------> Packet Encoder -------> Packet
> Decoder --------->File Sink 2
>                                                                           \
>                                                                        
>    \---------------> File Sink 1
> If the File Source loads a small-size image (around 50 kB), then the
> Packet Decoder works properly and File Sink 2 can open the image.
> However if the File Source load a bigger image or video (9 MB, for
> example), then the File Sink 2 achieve only more than 1 MB, and it can
> only display a part of the image/video. This surprised me.
> 
> Then I added a File Sink right after the Packet Encoder (it's called
> File Sink 1) to see what happened after the Packet Encoder. If I let the
> Sample Rate = 32k, then the File Sink 1 receives more than 9 MB, but the
> File Sink 2 still receive more than 1 MB. If I let the Sample Rate be
> faster, 1M or 4M, then both the File Sink 1 and File Sink 2 only get
> more than 1MB.
> I wonder if something related to CPU got out of ability with high Sample
> Rate or Packet Encoder - Packet Decoder 
> 
> Best Regards,
> V-L
> 
> Van-Ly Nguyen,
> Signals and Systems of Laboratory - SSL  
> Faculty of Electronics and Telecommunications - FET         
> University of Engineering and Technology - UET      
> Vietnam National University, Hanoi - VNU  
> 
> Tel: (+84) 978 819 406
> 
> 
> 
> On Wed, Jul 30, 2014 at 9:19 PM, Martin Braun <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     On 07/30/2014 04:14 PM, Nguyễn Văn Lý wrote:
>     > Thank you Tom,
>     >
>     > I found a note in documentation of the *Packet Encoder *block**
>     where it
>     > declares that the *Packet Encoder* is for use with the gnuradio
>     > modulator blocks: GMSK, DPSK, QAM. I don't know why only these
>     modulator
>     > blocks are supported, but not some popular things like BPSK or QPSK.
>     > Another thing is that my task requires the use of OFDM.
> 
>     These should also work (they are basically subsets of QAM), but *you*
>     have to make sure the absolute phase is correct *before* going into the
>     packet decoder.
> 
>     > Suppose now I have a simple flow graph as below:
>     > File Source -------> Packet Encoder -------> Packet Decoder --------->
>     > File Sink
>     > I wonder what types of file can be loaded and processed properly
>     in the
>     > *File Source* block (text, image, or video ...), and the same question
>     > for the *File Sink* block :-)
> 
>     Any file. The packet blocks really don't care about the contents.
> 
>     M
>     >
>     > Thank you so much
>     > Van-Ly
>     >
>     >
>     > Van-Ly Nguyen,
>     > Signals and Systems of Laboratory - SSL
>     > Faculty of Electronics and Telecommunications - FET
>     > University of Engineering and Technology - UET
>     > Vietnam National University, Hanoi - VNU
>     >
>     > Tel: (+84) 978 819 406
>     >
>     >
>     >
>     > On Wed, Jul 30, 2014 at 8:24 PM, Tom Rondeau <address@hidden
>     <mailto:address@hidden>
>     > <mailto:address@hidden <mailto:address@hidden>>> wrote:
>     >
>     >     On Wed, Jul 30, 2014 at 4:44 AM, Nguyễn Văn Lý
>     >     <address@hidden <mailto:address@hidden>
>     <mailto:address@hidden
>     <mailto:address@hidden>>> wrote:
>     >
>     >         Hi all,
>     >
>     >         Can anyone tell me what do *Packet Encoder* and *Packet
>     Decoder*
>     >         blocks do? and it would be great if you can give me some
>     example
>     >         :-)
>     >         Thanks in advance
>     >
>     >         Van-Ly
>     >
>     >
>     >     These are very simple example blocks to show you how to packetize
>     >     data. Packet bytes go in, they get wrapped into a packet of a
>     given
>     >     payload length with a header, access code, and preamble. The
>     header
>     >     is just a 2x repetition of the payload length (16 bits for each
>     >     field). Leaving the preamble and access code blank just
>     chooses the
>     >     defaults.
>     >
>     >     The decoder just looks for the access code with the number of
>     >     available bits wrong. When it's found, it reads the header to get
>     >     the payload length, extracts the payload, and outputs the payload.
>     >
>     >     Hope this helps.
>     >
>     >     Tom
>     >
>     >
>     >
>     >
>     >
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