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Re: [Discuss-gnuradio] dummy block has huge impact on usability fir filt
Re: [Discuss-gnuradio] dummy block has huge impact on usability fir filter
Mon, 17 Jan 2005 19:38:09 +0100
Mozilla Thunderbird 0.9 (X11/20041124)
Eric Blossom wrote:
On Mon, Jan 17, 2005 at 01:32:48AM +0100, Martin Dvh wrote:
Can you please update gnuradio-core
(gnuradio-core/src/lib/runtime/gr_single_threaded_scheduler.cc is the
file that matters) and try your test with and without the dummy block?
I am compiling the new version right now. I will let you now the results as
soon as possible.
extensive results at:
file used to generate results:
log of the session:
generated output files:
What I did was use my old driver which requires a high output_multiple.
I did an am_demodulation (like before) of a 5.0225 Mhz am modulated signal from
a signal generator (modulation is a sinewave of I think 1 kHz)
If I use the dummy block the results are as follows.
Filter narrower as 2436.2 Hz gives a number of taps above 16015 and I have a
silent output signal(like before).
Filter between 2436.2 and 4000 Hz does give output but is sounds strange. It is not a nice sine wave but sounds like the filter is resonating.
If I stop the input it takes a while for the sound to fade away.
maybe this is normal for very narrow filters.
This behaviour I already get some time now but I think in the older cvs versions ( more then a month ago) the result was different. I am not
sure about this. (I do have an older cvs version around so I may try to test this if I find the time)
with filters wider then 4000 Hz the output-signal starts to get normal.
If I do NOT use the dummy block I always get some output.
with trans_width wider then 4000 Hz the output starts to get normal.
below 4000 hz The sound is an intermittand sinewave.
It sounds like morse-code.
The narrower the filter, the longer the silence between the beeps.
If I use a transition width of 300 Hz the beeps are dozens of seconds apart.
you can listen to all output files.
I made a float filesink (audio_rate is 32127)
If you use it as a float filesource and connect it to dsp you can hear all
the audio_rate, transition bandwidth and wether or not dummy_block is used is
in the filename.
you can read the number_of_taps of every test in the log: