Re: [Discuss-gnuradio] Using the BCH and LDPC encoder from DVB-S2

[Ron Economos]

Yes, you can use the BCH and LDPC blocks stand alone. However, the size 
of the input data block will be determined by the code rate and frame 
size. For example with the LDPC block, a code rate of 2/3 with normal 
frame size (64800 bits) would require input blocks of 43200 bits (5400 
bytes). In the DVB-S2 specification, this number is called Nbch.

I had considered making the I/O pins on the LDPC and BCH blocks vectors 
(so that the above would be obvious), but felt it was too much work for 
not much in return (assuming they would never be used stand alone).

The parity bits are appended at the end of the input block. So in the 
above example, you'll see your original 43200 bits followed by 21600 
parity bits. Note that the parity bits are differentially encoded.

Ron

On 06/07/2016 03:26 PM, Jose Ruvalcaba wrote:
> Hello all,
>
>  I was wondering if in order to use the DVB-S2  BCH and LDPC encoder I 
> would have to use the header, scrambler, DVB-S2X modulator and 
> physical layer frame blocks in my Tx side. In other words, can I use 
> the FEC encoders from DVB-S2 stand alone? Also, is the data coming out 
> from the DVB-S2 LDPC encoder symmetric, that is it has the information 
> bits first then the parity bits? I'm currently trying to decode the 
> data coming from the BCH/LDPC encoded data without any of the other 
> blocks and have not been seeing the results I expect.
>
>
> Thanks,
> Jose