Re: [Discuss-gnuradio] Custom Blocks and Number of Items Per Port

[Tom Rondeau]

On Wed, Aug 1, 2012 at 3:46 PM, Alexander Olihovik <address@hidden> wrote:
> Hi all!
> I'm writing a custom sink block in Python with multiple input ports of all
> the same data type.
> I've been reading Josh's block coding guide, but I'm confused at one point:
> The value returned by a block should be the number of items produced by that
> block.
> Is this to say that if I have multiple ports, I may return the value of
> input_items[0]?
> Or is it correct to say that I must return the sum of all input_items[i], i
> = range(number of input ports)?
>
>
> I would like to create a synchronous block where all ports consume and
> produce an equal number of items every time the work function is called.
> However, it appears that there are times when input_items[0] !=
> input_items[1] != ... != input_items[numPorts-1]
> If I were to return input_items[0], I would assume that this would not yield
> the results I expect!
>
> Any help is greatly appreciated!
>
> From,
> Alex

If you have a block with multiple input items and you want to produce
the same number every time, noutput_items will tell you how much you
are capable of producing on every output stream. When you 'return
noutput_items', you are saying that you have produced that many items
on EVERY stream.

There is another way that specifies the same thing. Each block
consumes some number of samples on every input stream and produces
some number of samples on every output stream. You can individually
specify "produce(i, N_i)" and "consume(o, N_o)" on each input and
output stream, respectively. In this case i is the input stream and
N_i is the number of items consumed on that input stream and o is the
output stream and N_o is the number of items consumed on that output
stream. When specifying your own 'produce' values, though, make sure
to return WORKED_CALLED_PRODUCE, to tell the scheduler that you have
done this yourself. But it sounds like you want to produce the same
amount on every stream, so you should be fine just using 'return
nouput_items'.

Tom