Forum: GNU Radio dumb question: history

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Charles S. (Guest)
on 2007-04-26 14:59
(Received via mailing list)
How does 'history' relate to i/o data indices? I assume you cannot have
an index < zero.

Say your work function gets common i/o arrays

  const float *in = (const float *) input_items[0];
  float *out = (float *) output_items[0];

and you set_history(ntaps), I guess that means you get ( noutput_items +
ntaps ) for the number of intput items and can produce noutput_items

Now I have two streams, one is pass-thru (symbol tags) and the other is
the data to be filtered and gets delayed by ntaps.

The filtered stream is processed by:

  d_equalizer->filter (in, in_tags, out, noutput_items);

where out[x] is the processed sample in[x + ntaps] (?).

So to keep the symbol tags aligned, should we use:

  for (int i = 0; i < noutput_items; i++)
    out_tags[i] = in_tags[i + d_offset];

d_offset = ntaps - npretaps - 1

Is that the correct thinking? size of out[] is noutput_items and size of
in[] is noutput_items + history ?? history = ntaps, and is  > ntaps
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