On 27/11/2022 17:23, Marcus D. Leech wrote:
On 27/11/2022 05:26, Daniel Estévez wrote:
Hi,
Another option for extracting one or a range of items from a vector
is to use Vector to Stream followed by Keep 1 in N or Keep M in N.
See near the bottom of this flowgraph for an example:
https://github.com/daniestevez/reu-2022/blob/main/polyphase/polyphase_filter.grc
Best,
Daniel.
That would only allow the first or first-N of the streams to be
captured, rather than some arbitrary single stream, no?
No, because these blocks have an initial offset parameter (and if they
didn't, we could use "Skip Head"). As an example, say that we have
1024-point FFTs given as vectors and we only want the FFT bin number 42.
We do vector to stream, then Keep 1 in N with N = 1024 and initial
offset = 42. This would give us a stream where only the FFT bin number
42 appears.
Now say that w want FFT bin numbers 42, 43, 44, 45. We do vector to
stream, then Keep M in N with N = 1024, M = 4, initial offset = 42.
This would give us a stream that contains:
bin_42(t0), bin_43(t0), bin_44(t0), bin_45(t0), bin_42(t1),
bin_43(t1), bin_44(t1), bin_45(t1)...
If desired, we can turn this into vectors of 4 elements using stream
to vector or use a deinterleave block to separate each of the bins in
its own stream.
Best,
Daniel.