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[Discuss-gnuradio] RE: Timestamp value
From: |
Ulrika Uppman |
Subject: |
[Discuss-gnuradio] RE: Timestamp value |
Date: |
Thu, 18 Feb 2010 17:14:59 +0100 |
Oops, the printuts seems to have been mosched together in the mail, here is
that part once again:
ts_in = 1435221596, ts_last = 0, diff = 1435221596
ts_in = 2560802396, ts_last = 1435221596, diff = 1125580800
ts_in = 3367616092, ts_last = 2560802396, diff = 806813696
ts_in = 4174429788, ts_last = 3367616092, diff = 806813696
ts_in = 686341724, ts_last = 4174429788, diff = 806879232
ts_in = 1493155420, ts_last = 686341724, diff = 806813696
ts_in = 2283192156, ts_last = 1493155420, diff = 790036736
ts_in = 3090005852, ts_last = 2283192156, diff = 806813696
ts_in = 3896819548, ts_last = 3090005852, diff = 806813696
ts_in = 408731484, ts_last = 3896819548, diff = 806879232
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden
> On Behalf Of Ulrika Uppman
> Sent: Thursday, February 18, 2010 5:10 PM
> To: address@hidden
> Subject: [Discuss-gnuradio] Timestamp value
>
> Hi,
> I wonder how the timestamps are being generated for each
> ethernet-packet sent from the USRP2 to the host? My initial
> idea about how it works was that timestamps are generated at
> 100MHz (same as the samples) and then the timestamp
> associated with the first sample in an ethernet data packet
> will be put in the metadata which could then be unpacked in
> the host. I then would assume that the next packet after the
> first one will have a timestamp value that is proportional to
> the number of samples per packet times the decimation rate.
> However I get timestamp values that increase much much more
> for each received packet, so I wonder if my idea of how
> timestamps are generated is wrong?
>
> I run the stable 3.2 version of gnuradio on Ubuntu 9.04 and I
> have an USRP2 with the RFX2400. (I also was going to try the
> gnuradio trunk but I got problems with building, see my other
> post "Error on make from git development trunk"). I tried
> both an old version of the fpga bin-file and one that I just
> recently downloaded (but both gave the same result).
>
> I put some printouts in usrp2_impl.cc in the
> handle_data_packet function and the output when I run
> rx_streaming_samples then looks like this:
> ./rx_streaming_samples -f 2457e6 -d 16 -N 400 -v
> ..............................................................
> .....................
> Daughterboard configuration:
> baseband_freq=2456250000.000000
> ddc_freq=-750000.000000
> residual_freq=-0.016764
> inverted=no
>
> USRP2 using decimation rate of 16
> Receiving 400 samples
>
> ts_in = 1435221596, ts_last = 0, diff = 1435221596 ts_in =
> 2560802396, ts_last = 1435221596, diff = 1125580800 ts_in =
> 3367616092, ts_last = 2560802396, diff = 806813696 ts_in =
> 4174429788, ts_last = 3367616092, diff = 806813696 ts_in =
> 686341724, ts_last = 4174429788, diff = 806879232 ts_in =
> 1493155420, ts_last = 686341724, diff = 806813696 ts_in =
> 2283192156, ts_last = 1493155420, diff = 790036736 ts_in =
> 3090005852, ts_last = 2283192156, diff = 806813696 ts_in =
> 3896819548, ts_last = 3090005852, diff = 806813696 ts_in =
> 408731484, ts_last = 3896819548, diff = 806879232
>
> Copy handler called 2 times.
> Copy handler called with 2968 bytes.
>
> Elapsed time was 0.000 seconds.
> Packet rate was 100000 pkts/sec.
> Approximate throughput was 148.40 MB/sec.
> Total instances of overruns was 0.
> Total missing frames was 0.
> ..............................................................
> .....................
>
> ts_in is the timestamp found in the metadata of the packet
> just received, ts_last is the one from previous packet and
> diff is just the difference them between. Since there seems
> to be no missing frames I'm guessing the big value of diff
> can't be related to lost packets?
> If I try different decimation rates, I see no obvious
> relation between the difference in value between two timestamps...
>
> Do anyone know why the difference in timestamp value between
> received packets is so big? What am I missing here?
>
> Thanks,
> /Ulrika
>
> _______________________________________________
> Discuss-gnuradio mailing list
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> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
- [Discuss-gnuradio] Timestamp value, Ulrika Uppman, 2010/02/18
- [Discuss-gnuradio] RE: Timestamp value,
Ulrika Uppman <=
- Re: [Discuss-gnuradio] RE: Timestamp value, Per Zetterberg, 2010/02/18
- RE: [Discuss-gnuradio] RE: Timestamp value, Ulrika Uppman, 2010/02/19
- RE: [Discuss-gnuradio] RE: Timestamp value, Ulrika Uppman, 2010/02/19
- Re: [Discuss-gnuradio] RE: Timestamp value, Josh Blum, 2010/02/19
- RE: [Discuss-gnuradio] RE: Timestamp value, Ulrika Uppman, 2010/02/22
- RE: [Discuss-gnuradio] RE: Timestamp value, Ulrika Uppman, 2010/02/23
- RE: [Discuss-gnuradio] RE: Timestamp value, Per Zetterberg, 2010/02/23
- Re: [Discuss-gnuradio] RE: Timestamp value, Josh Blum, 2010/02/23
- RE: [Discuss-gnuradio] RE: Timestamp value, Ulrika Uppman, 2010/02/25
Re: [Discuss-gnuradio] Timestamp value, Tim Pearce, 2010/02/18