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[Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter
From: |
Vincenzo Pellegrini |
Subject: |
[Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter |
Date: |
Tue, 11 Nov 2008 08:26:11 +0100 |
Martin ,
sorry for the delay. My exams seem to have gone well even if it's not
official yet. I also had to do a demo for a company I have a temporary
contract with for developing some gnuradio based gsm-r security
sentinels. Also the demo was smooth. (i already listed the project on
the gnuradio wiki)
so i really hope i'll be able to prepare the 8Mhz stream for you
within the next 2/3 days. Would this still be useful?
2008/11/3, Martin DvH <address@hidden>:
>
> On Mon, 2008-11-03 at 14:13 +0100, Martin DvH wrote:
>>
>>
>>
>> ________________________________
>>
>> > Van: address@hidden
>> [mailto:address@hidden
>> 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 checked now. It is a:
> Western digital Scorpio 320 GB SATA (WDC WD3200BEVT-22ZCT0)
> 2.5-inch SATA Hard Drive 320 GB, 3 Gb/s, 8 MB Cache, 5400 RPM
>
> Benchmark from tomshardware (h2benchw 3.6):
> http://www.tomshardware.com/charts/2-5-hard-drive-charts/Minimum-Read-Transfer-Performance,687.html
> minimum read transfer rate 33.5 MB/sec
> average read transfer rate 52.2 MB/sec
> maximum read transfer rate 68.2 MB/sec
>
>
>
>> 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 <address@hidden>
>>
>>
>>
>> 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
>> <address@hidden>
>> > > 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
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>
>
--
Vincenzo Pellegrini
- [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Vincenzo Pellegrini, 2008/11/01
- [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Martin DvH, 2008/11/02
- [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Martin DvH, 2008/11/02
- [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Vincenzo Pellegrini, 2008/11/02
- RE: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Martin DvH, 2008/11/03
- RE: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Martin DvH, 2008/11/03
- [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter,
Vincenzo Pellegrini <=
- Re: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, rafael2k, 2008/11/11
- [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Vincenzo Pellegrini, 2008/11/11
- Re: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter, Martin DvH, 2008/11/14