Re: [Discuss-gnuradio] Timesample/Ethernet Fifos

[Doug Geiger]

Tim Pearce wrote:
> Hi All,
>
> I've modified the source to generate timesamples (as a seperate 
> stream) from the USRP2 source blocks and noticed an issue - if the PC 
> is struggling some frames have a timesample dated before the 
> timesample of a frame processed before it.
>
> It's possible I've done something wrong modifying the code but I think 
> this is a host issue as the problem is reduced (i.e it only happens at 
> lower decimation rates) on faster machines.
>
> Has this been seen before? Are there any kernel options etc that might 
> improve this? I'd assumed the ethernet bit was a FIFO buffer of some 
> sort but guess this isnt working quite right.
>
> Tested on Ubuntu 9.04 (Jaunty).
>
> Cheers,
>
> Tim

Tim,
You're taking the source and outputting a timestamp for each sample? 
Are you taking the timestamp for the frame, and then just incrementing 
according to decimation, until you get to a new frame then?
I haven't noticed such peculiarities when I look at my timestamps - but 
thus far I'm mainly looking just at the frame-by-frame timestamp.
Doug

--
Douglas Geiger
Code 5545
U.S. Naval Research Laboratory
Washington, DC 20375
(202) 767-9048
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