Hello,
I am having a hard time trying to correct a block that calculates
autocorrelation with overlapping.
Having read about set_history(), consume_each() behaviour of the block
does not match my size calculations.
- Should consume_each include the N-samples that are stored in history
or not? (I guess history samples indices are calculated based on what is
provided in consume_each())
The code of the block is as follows:
...
//setting parameters in constructor:
d_nonoverlap_size = d_snapshot_size-d_overlap_size;
set_history(d_overlap_size+1);
//determine input/output buffer sizes relationship (in connected blocks)
set_relative_rate(1.0/d_nonoverlap_size);
...
Then there is forecast:
...
// Setup input output relationship
for (int i=0; i<ninput_items_required.size(); i++)
ninput_items_required[i] = d_nonoverlap_size*noutput_items;
...
And general work:
int
autocorrelate_impl::general_work (int output_matrices,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
// Cast pointer
gr_complex *out = (gr_complex *) output_items[0];
// Create each output matrix
for (int i=0; i<output_matrices; i++)
{
// Form input matrix
for(int k=0; k<d_num_inputs; k++)
{
memcpy((void*)d_input_matrix.col(k).data(),
((gr_complex*)input_items[k]+i*d_nonoverlap_size),
sizeof(gr_complex)*d_snapshot_size);
}
// Make output pointer into matrix pointer
Eigen::Map<Eigen::MatrixXcf> out_matrix(out+d_num_inputs*d_num_inputs*i,
d_num_inputs,d_num_inputs);
// Do autocorrelation
out_matrix = (1.0/d_snapshot_size)*d_input_matrix.transpose()*d_input_matrix
.conjugate();
if (d_avg_method == 1)
out_matrix = 0.5*out_matrix+(0.5/d_snapshot_size)*d_J*out_matrix.conjugate()
*d_J;
}
// Tell runtime system how many input items we consumed on
// each input stream.
consume_each (d_nonoverlap_size*output_matrices+d_overlap_size);
// Tell runtime system how many output items we produced.
return (output_matrices);
}
When the block is simulated in comparison to no (0) overlap it returns
strange values probably due to sizing issues, some historical samples
distort the result.
[image: buffering_issue.png]
Whole code and more complex test
case(music_algo_simulation_2rx_with_noise.grc) is available here:
https://github.com/MarcinWachowiak/GNU-Radio-USRP-Beamforming
Please advise.
Kind regards,
Marcin Wachowiak
