Dear Marcus, Thank you for quick and detailed answer.
I'll check that gr-eventstream as well as fundamentals of GNU Radio you've described. Regards, Jeon. 2015-10-21 22:23 GMT+09:00 Marcus Müller <marcus.muel...@ettus.com>: > Hi Jeon, > > with gr-eventstream, there's something that already does the "idle time > padding": > https://github.com/osh/gr-eventstream/ > Read Tim's articles, too: > http://oshearesearch.com/tag/gr-eventstream/ > > To answer your question: > > 1. Is it allowed to forecast zero item? And does it behave as I expect? > > Well, yes, and no :) > First: your Pad Idle block is a stream source (It doesn't have a stream > input, only a message input); you don't have to implement a forecast, just > use a sync block type (or the source block type that gr_modtool offers you > to generate). > Generally, it's right to tell GNU Radio you can't produce anything with > the current input, but: > stream sources are a little special, as they *never* get input, so from > GNU Radio's perspective, the input situation can't ever change. So telling > GNU Radio you can't produce anything will make your flow graph stop. As a > side note, I've never thought about whether forecast ever gets called on a > source -- basically, what should that do? There's not ninput_required array > with nonzero length to be filled with values on a block with no inputs! > > 2. If forecasting zero item is possible, willl general_work() be called > extremely frequently so that other blocks are prevented from being called? > > There's no "preventing other blocks from being called". GNU Radio is > multithreaded, and as long as there's stuff to be done, the other blocks > will be called until all buffers have run dry. > > The point here is that you should just block in your work function if > you're a source. However, with the modern message passing alone, that's > impossible, because messages are always delivered when your work is > currently *not* running. Hence, gr-eventstream takes a queue approach, > and that works pretty well. > > Best regards, > Marcus > > > > > On 10/21/2015 02:53 PM, Jeon wrote: > > Consider a flow graph like: http://i.imgur.com/bNa6YuQ.png > > > > Message source produces a short message. Period is quite long. Thus, There > should be a long idle time. > > I'd like to build a block 'pad idle'. The block pad a predefined sequence > if the upstream block gives nothing. > > I think a prototype would be: > https://gist.github.com/gsongsong/d40b85a76ab8e80ae468#file-gistfile1-txt-L11 > > By setting the number of required items to zero in forecast(), > general_work() will be called even there is no items received. And general > work() checks the ninput_items and if it is zero, generates some > idle-padding samples/patterns. Otherwise, it just handles and passess a > message/samples to downstream. > > But it's just my thought. There may be a couple of considerations. > > 1. Is it allowed to forecast zero item? And does it behave as I expect? > 2. If forecasting zero item is possible, willl general_work() be called > extremely frequently so that other blocks are prevented from being called? > > Regards, > Jeon. > > > _______________________________________________ > Discuss-gnuradio mailing > listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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