Re: [Discuss-gnuradio] Timesample/Ethernet Fifos

[Juha Vierinen]

We're checking timestamps on ethernet frames and everything seems fine
all the way up to 25 MHz over many hours of continuous data streaming.
At lower rates we've done several days of streaming without dropped
frames or conflicting timestamps.

juha

On Tue, Nov 10, 2009 at 20:21, Tim Pearce <address@hidden> wrote:
> Hi Doug,
>
> Yes for each sample its calculating the new sample value by adding the
> decimation rate.
>
> I'll try this without the addition as it might reduce the processor load and
> can easily be post processed for the application I'm working on.
>
> Cheers,
>
> Tim
>
> On Mon, Nov 9, 2009 at 10:06 PM, Doug Geiger <address@hidden>
> wrote:
>>
>> 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
>> address@hidden
>>
>
>
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