# I & Q samples in a source module **URL:** \ **Category:** GNU Radio\ **Created:** [May 9, 2015, 6:43am UTC](https://www.ruby-forum.com/t/i-q-samples-in-a-source-module/241893 "2015-05-09T06:43:56Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [May 9, 2015, 6:43am UTC](https://www.ruby-forum.com/t/i-q-samples-in-a-source-module/241893/1 "2015-05-09T06:43:56Z")
My source modules has 16-bit I & Q samples that are interleaved: I,Q,I,Q,I,Q… as signed 16 bit values. I generate 512 pairs at a time in my work function (C++). I set noutput\_items to 512 and copy I and Q out 512 times to the output\_items variable in the work function. Is this the correct format of data that subsequent modules can expect? I use the IShort\_to\_Complex module to convert the samples for subsequent modules. Thanks, Y- ---
**Author:** ![Yile\_Ku](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/77aa72/32.png) [@Yile\_Ku](https://www.ruby-forum.com/u/Yile_Ku)\ **Post date:** [May 9, 2015, 1:12pm UTC](https://www.ruby-forum.com/t/i-q-samples-in-a-source-module/241893/2 "2015-05-09T13:12:59Z")
Hi Y, > I set noutput\_items to 512 > no, noutput\_items is the maximum number you’re _allowed_ to produce, it > doesn’t change anything if you set it to anything. You just return the > number of items you’ve produced at the end of your work (or > general\_work) function. Make sure to not write more items than > noutput\_items allows you to do! If you’re returning 512, this tells the scheduler you’ve produced 512 _items_ – I don’t know what your block’s output signature looks like, but an item has the size of 2x 16bit, it’s right. Best regards, Marcus ---
**Author:** ![Yile\_Ku](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/77aa72/32.png) [@Yile\_Ku](https://www.ruby-forum.com/u/Yile_Ku)\ **Post date:** [May 10, 2015, 11:35am UTC](https://www.ruby-forum.com/t/i-q-samples-in-a-source-module/241893/3 "2015-05-10T11:35:36Z")
Y, yes, if you’re producing 512 I+Q, you’re actually producing either 1024 items of sizeof(unsigned short) or 512 items of sizeof(unsigned short)\*2. I’d like to repeat that you _must_ make sure that the number of items you write into your output buffer is ??? noutput\_items! What kind of block are you writing? Best regards, Marcus