[Discuss-gnuradio] dummy block has huge impact on usability fir filt(Martin)

[rana nalla]

 Hi all,

              This was the bug mentioned in December by Mr. Martin and
now iam having the same problem. Iam trying to demodulate a QPSK
signal and during the carrier recovery process, iam trying to multiply
the filtered, squared signal with the signal but it is not giving any
ouput. The output blinks on the scope for a second and then remains
calm. Is this really buffer allocation problem, if it so then may I
know if it is fixed or not. Thank you all for suggestions. Iam
attaching a small test program that illustrates this problem.

 Rana.

  #............. Program to illustrate the bug ....................#

from gnuradio import gr
from gnuradio import audio
import sys
import math

def build_graph ():
        
        fg = gr.flow_graph ()

        samps_per_symbol = 32
        samp_freq =16000
        carrier_freq = 1900
        src = gr.file_source(gr.sizeof_float, "qpsk_input_num")
        dst = audio.sink (samp_freq)

#............... Band Pass FIltering at the front end of the reciever
................... #

        audio_coeffs1 = gr.firdes.band_pass (
                1.0,    # gain
                samp_freq,
                1400,   # center of low transition band
                2400,   # center of hi transition band
                600,    # width of transition band
                gr.firdes.WIN_HAMMING)

        audio_filter1 = gr.fir_filter_fff ( 1, audio_coeffs1)
        i_demod_mixer = gr.multiply_ff()

        fg.connect(src,audio_filter1)
        fg.connect(audio_filter1,(i_demod_mixer,0))
        fg.connect(src,(i_demod_mixer,1))
        fg.connect(i_demod_mixer,(dst,0))
        fg.connect(src, (dst,1))
        
        return fg
        
def main ():
        fg = build_graph()

        fg.start()
        raw_input ('Press Enter to quit')
        fg.stop()

if __name__ == '__main__':
        main ()