Re: [Discuss-gnuradio] I & Q samples in a source module

[Marcus Müller]

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

On 05/09/2015 05:48 PM, Yile Ku wrote:

Marcus,

Thanks,  Actually the size I set for the blocks output signature is 16 bits (unsigned short),  Should it be 32-bits for a combined I & Q sample? 

Y-

On Sat, May 9, 2015 at 5:11 AM, Marcus Müller <address@hidden> wrote:

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

On 05/09/2015 06:42 AM, Yile Ku wrote:

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-

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