________________________________
> Van: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
Namens Vincenzo Pellegrini
> Verzonden: maandag 3 november 2008 0:16
> Aan: Martin DvH
> CC: discuss-gnuradio
> Onderwerp: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter
>
>
> This is Great... :)
>
> Yup, the playback cannot be smooth because of the wrong throughput,
definitely.
> Did you use the USRP1 with interpolation factor = 16 ?
Yes I did.
>
> I can prepare a modulated signal with the correct throughput for
you.. this is not a problem... :)
>
Please do, this would be great.
> what hard disc are you playing your signal back from?
Internal 2.5" harddisk of my acer 6930 notebook (Aspire 6930G-734G32BN
LX.AVB0X.135)
2.5" 320GB HDD 5400rpm, SATA
I am not at home right now So I can't check the exact brand and model of the
harddisk.
It can do around 38 MB/sec so this is just enough (required 32 MB/sec)
I also have 4GB of memory in this notebook, so I think it will buffer the
complete file.
I had to use my notebook because with my desktop PC (ASrock 939-DUAL-SATA2)
The USB TX bandwidth is less then 32 MB/sec.
(Which is strange because I CAN receive 32 MB/sec)
I get UuUuUu on this machine when useing interpolation 16, so unusable.
Regards,
Martin
>
> regards
>
> vincenzo
>
>
> 2008/11/3 Martin DvH <[EMAIL PROTECTED]>
Hi,
> > In fact: 8 complex Msps implement a 7 MHz channel while
9.142857143
> > complex Msps implement an 8 MHz channel.
> > Just try to go as close as possible to such sampling
frequency by
> > using USRP2 and let me know what happens... it could
turn out that we
> > need a resampler block.
> So if I use a fractional rate resampler with interpolation
factor
> 10/8=1.25 I get a 7 Mhz channel with 10 Msps samplerate.
> If I use a fractional rate resampler with interpolation
factor
> 10/9.142857143=1.09375 I get a 8 Mhz channel with 10 Msps
samplerate
>
> If I use a fractional rate resampler with DECIMATION
factor
> 9.142857143/8=8/7=1.142857143 I get a 8 Mhz channel with 8
Msps
> samplerate with the out-of-band skirts folded back at the
sides.
>
> Would be interesting to see if this last one works with a
USRP1.
>
> I'll let you know how the experiments go.
I resampled and scaled your ofdm_40.dump file so it now will
use 8 Mhz bandwidth with a 8 Msps samplerate.
The reception never can be perfect this way but it seems
good enough for
tests.
My USB DVB-T receiver receives the transport stream without
problems.
Mplayer playes the stream without problem for two loops and
then crashes
with a broken frame.
My standalone settopbox DVB-T receiver now also receives the
stream.
(8 MHz channel on UHF)
It has big problems displaying it. Sound is only a chop of
sound now and
then and video stops, then runs for a second, then stops
again.
I think this is because the timestamps and framerate
(playout speed)
don't match the data throughput of the MPEG stream anymore.
(It is getting the stream too fast)
I put my resampled RF file at:
http://www.olifantasia.com/projects/gnuradio/mdvh/OTA/DVB-T/ofdm_40_bw8Mhz_s
amplerate_8Msps_cshort.raw
format is complex signed short integers (I 16 bit, Q 16 bit)
at 8
Msamples/sec.
Greetings,
Martin
> > more details will follow as soon as I find some time...
> Thanks and success with your second group of tests.
>
> Martin
> > best regards and greetings
> > to all fellow GNURadioers
> >
> > vincenzo
> >
> > PS
> > Rafael, just have a look back a this thread and you'll
find all the
> > info you need to do your test broadcast. Thanks for your
interest
> >
> >
> >
> >
> >
> >
> > 2008/10/31 Martin Dudok van Heel
<[EMAIL PROTECTED]>
> > Hi Vincenzo.
> > How are things going with your exams.
> >
> > I hope well.
> >
> > Thanks for your help so far.
> >
> > I finally got your DVB-T dump streams working.
> > I first tried using an undersampled basicTX but
never got it
> > to work.
> > (use a niquist mirror in the VHF range on
channel 11 or 12
> > (219.5 Mhz or 226.5 Mhz))
> >
> > I now use a RFX900 and that works with a
pinnacle PCTV-Solo
> > 72e usb DVB-T receiver card plugged into my PC.
> > I use 858.0 Mhz (channel 69)
> > I used a 10 dB attenuator on the antenna output
to limit
> > output power.
> > I also modified the RFX900 to enable
transmitting outside of
> > the ISM band. (disable saw-filter. add 220 pF
capacitor)
> >
> > Apparantly the pinnacle 72e can receive 7 Mhz
channels on the
> > UHF channels.
> > My standalone settopbox DVB-T receiver can't
handle it.
> >
> > I noticed you don't use the full possible range
in your 16 bit
> > streams.
> > (only goes from -80 to +80 while you could use
-8192 to 8192)
> > Is this on purpose?
> > I can multiply samples by 64 and get a cleaner
signal. (But
> > also more output power)
> >
> >
> > I do have a request, I hope it is not too much
work.
> > Could you make a stream with 10 Msamples/sec
samplerate and 8
> > Mhz wide channel.
> > This way I can use standard standalone DVB-T
receivers and
> > don't have the 7Mhz bandwith on UHF problem.
> >
> > For the 10 Msps stream I would have to use my
USRP2 to output
> > it.
> > It has a 100 Mhz DAC (in stead of 64 Msps in the
USRP1)
> > It has a gbit ethernet connection for the
samples, so I can go
> > up to 25 Msps.
> > It can only do fixed interpolation rates so I
have to choose
> > from the table below.
> > (8 Msamples/sec is not supported on the USRP2)
> >
> >
> > USRP2
> > dac_rate interp ethernet_sample_rate
> > 100 4 25
> > 100 5 20
> > 100 6 16.67
> > 100 7 14.29
> > 100 8 12.5
> > 100 9 11.11
> > 100 10 10 <----I think 10
Msamples/sec
> > should be optimal
> > 100 11 9.09
> > 100 12 8.33
> > 100 13 7.69
> > 100 14 7.14
> >
> >
> > I think 10 Msamples/sec would be a good
candidate.
> >
> > Have you also tried using 8 Msamples/sec on the
USRP1?
> > I know there would be no room left for IF
channel filtering,
> > but it could in theory still work.
> > If this works I would also very much appreciate
a 8Mhz
> > bandwidth stream with 8 MSPS samplerate so I can
demonstrate
> > with a standard USRP1.
> >
> > Thanks for your help so far.
> > I appreciate it very much.
> >
> > And good luck with your exams.
> >
> > Have a nice weekend.
> >
> > Greetings,
> > Martin
> >
> >
> >
> >
> > --
> > Vincenzo Pellegrini
--
Vincenzo Pellegrini
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