RE: [Discuss-gnuradio] Re: Soft-DVB DVB-T transmitter

[Martin DvH]

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
>       
> 
> 
> 
> 
> 
> 
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