Re: [Discuss-gnuradio] Keep M in N

[Marcus Müller]

Highway to the _DANGER ZONE_ :D

No, really, we do check for N>=M: https://github.com/gnuradio/gnuradio/blob/master/gr-blocks/lib/keep_m_in_n_impl.cc#L58

      if(d_m > d_n) {
        std::string s = boost::str(boost::format("keep_m_in_n: m (%1%) <= n %2%") % d_m % d_n);
        throw std::runtime_error(s);
}

Sadly, we only do that in the constructor, not in the set_m and set_n . Maybe, just maybe, we should change that :D

Cheers,
Marcus

On 06.10.2016 17:00, Tim wrote:

I'd venture to say M>N is living in dangerous territory

On 10/06/2016 10:56 AM, Marcus Müller wrote:

Hi Steve,

The first M of each N. :) (I don't really understand 100% what "every N/M" would be in general for arbitrary N>=M, integers).

If you dare to venture into the GNU Radio source code (which I'd encourage you to do, it's just that this isn't the most beautiful/interesting block), you'll find that the implementation [1] simply memcopys the first m items of every n-chunk from in- to output.

Best regards,

Marcus

[1] https://github.com/gnuradio/gnuradio/blob/master/gr-blocks/lib/keep_m_in_n_impl.cc#L111

On 06.10.2016 16:22, Steve Gough wrote:

Hi mailing list,

I have a question regarding the Keep M in N block, which keeps M out of every N samples. Is this the first M samples in every N which it retains (or) is it every N/M ?

Thanks!

Steve

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