Re: [Discuss-gnuradio] Eventstream source latency

[Nick Foster]

I think you'll find that the merging is the problem. Gnuradio hangs onto rather large buffers, as does UHD, and in your case the buffer for the continuous stream will set the latency of the system rather than the eventstream PDU.

Try removing the constant stream and see if that changes the behavior you're seeing.

Nick

On Sat, Aug 17, 2019 at 3:27 PM Jacob Gilbert <address@hidden> wrote:

Hi Daniel

You might be interested in the gr-pdu_utils and gr-timing_utils modules. They are about to get a significant update but there is a decent writeup on the concept of operations in github.

Sub-ms latency is possible depending on host hardware and system configuration.

Jacob

On Fri, Aug 16, 2019, 10:08 Lundberg, Daniel via Discuss-gnuradio <address@hidden> wrote:

I have a flowgraph with a simple FDMA implementation with two channels.  One channel has a constant stream.  The other channel has complex sample bursts generated in a custom python function, which I package as a PDU.  I apply the frequency modulation within the python file to place it in the correct frequency channel.  I send the PDU to an eventstream source and then add the two channels in an add block before sending the merged signal to a USRP sink.  I am seeing latencies of over a second from the PDU generation to when the eventstream source sends them on.  My sample rate is ~5 Ms/s and my PDU is about 1.25 MS, so about a quarter of a second.  My eventstream source block is using ASAP event placement and MEMCPY settings.

Is this level of latency expected?  I do not fully understand the merge behavior of the eventstream source, but I would expect perhaps 2X the PDU size of latency if it has a PDU length number of zeros in it's buffer before inserting the PDU.

Thank you,
DL

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio