Forum: GNU Radio Limitations of gr_block: max_possible_items_available = 8191

Hello,

I created a block with a variable input rate, but when I
run the flowgraph I get the following error:

sched:  is requesting
more input data
 than we can provide.
 ninput_items_required = 16000

max_possible_items_available = 8191
 If this is a filter, consider
reducing the number of taps.

If I don't exceed the limit of 8191 items
the block works correctly but I need to exceed this limit for the
experiments I'm doing.

Is this a limitation of gr_block? Is there any
way to exceed this limit?

In the other way I tried to use
gr_sync_decimator but does not work because sometimes I need to consume
16000 ninput_items, sometimes 15999, and so on, and  gr_sync_decimator
seems to have a fixed rate.

Thank you in advance. Best regards.


Luis

On Tue, Aug 14, 2012 at 12:52:11PM +0200, luis@epsilon-formacion.com 
wrote:
>   If this is a filter, consider reducing the number of taps.
>
> If I don't exceed the limit of 8191 items the block works correctly but I need
> to exceed this limit for the experiments I'm doing.
>
> Is this a limitation of gr_block? Is there any way to exceed this limit?

I believe this is to do with the buffer limits between blocks (which are
set by the Linux kernel).

Do you *really* need this many input items per output item? If so, you
can also buffer manually, inside the block--here, there are no limits
other than the amount of RAM you have.

> In the other way I tried to use gr_sync_decimator but does not work because
> sometimes I need to consume 16000 ninput_items, sometimes 15999, and so on, and
> gr_sync_decimator seems to have a fixed rate.

Yep, it's fixed. Use a gr_block, and use set_relative_rate() to
1.0/16000 or whatever.

MB

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