[Hackrf-dev] Analog TV transmitter

[Paul Connolly]

> I don't know how to set offset to 5.5 Mhz for PAL B/G
Use a Frequency Xlating (translating) FIR Filter block (
http://www.csun.edu/~skatz/katzpage/sdr_project/sdr/grc_tutorial4.pdf )

As for NBFM or WBFM, I don't know, I haven't actually done it. Test ?

The  missing parts for video would be just sending a bunch of still
images in one part of the RF spectrum and in your particular case at the
same time a synchronised FM signal 5.5MHz away from the image stream.
Basically something that reads in a video file and changes the frame
rate to 25 frames a second, and kicks out individual images at  768 x
576 resolution (PAL - Vertical lines 625 ; Vertical lines visible 576 ).
(maybe something like "sudo apt-get install libav-tools ; avconv -i
myfile.avi  -s "720x576" -r 25 output_%d.jpg" would be  a basic starting
point)
And a second process that strips out the audio for encoding into FM and
delay control to sync up these two independent  processes. I'm not suite
sure how you would adjust the buffering to match the two independent
streams. Maybe do not worry about having them in sync to begin with.
(something like "avconv -i myfile.avi output.wav" could be  a starting
point to get the audio stream)

Probably best to start testing with a tiny 1-2 second video file, and
then eventually workout some way to avoid having to make actual
individual images files for each of the 25 frames a second (two fields a
frame, so 50 fields per second).



On 26/05/2015 10:56, Mitja kocjančič wrote:
> Thanks I try transmitting audio but I don't know how to set offset to 5.5
> Mhz for PAL B/G (Video works fine) and don't know how to set devitation to
> 25 khz (should I use NBFM Modulator block or WBFM Modulator block
>
> PS: How to encode Video in PAL? (any command in VLC (like in DVB-T where
> you can encode MPEG 4 with it)
> PPS: Is posible to encode and transmitt in real time (I start a movie in
> VLC then Video get encoded and Audio get transmitted using GNU Radio (can I
> use stdin and stdout pipes to fed encoded Video and Audio to GNU Radio?)
>
> Thanks for Anwsering and Best Regards
>
> 2015-05-26 5:25 GMT+02:00 Paul Connolly <eeipcy at gmail.com>:
>
>>  I don't think that anyone has transmitted teletext with the HackRF (yet)
>> , but I could be wrong ?
>> Teletext never caught on in the US, so you may have to go to the standard
>> http://www.etsi.org/deliver/etsi_i_ets/300700_300799/300706/01_60/ets_300706e01p.pdf
>>
>> The NTSC flow graph ( https://github.com/argilo/sdr-examples ) had some
>> modifications done to it and there is now a PAL flow graph (
>> https://github.com/miek/sdr-stuff )
>>
>> As for the Audio, it is a separate FM signal ( 25 kHz instead of 75 kHz
>> used for FM radio station) at an offset to the video carrier. And that
>> offset is different for a lot of the PAL broadcast systems
>> (PAL-B/D/G/H/I/K/M/N)
>> See this for the details for each PAL version:
>> https://en.wikipedia.org/wiki/PAL#PAL_broadcast_systems
>> There is a good graphic of the PAL transmission modulation scheme here
>> https://en.wikipedia.org/wiki/PAL#Colour_encoding
>> It is very similar to the one for NTSC  (
>> https://en.wikipedia.org/wiki/NTSC#Transmission_modulation_scheme ) which
>> might be useful for comparison.
>>
>>
>>
>> On 25/05/2015 07:59, Mitja kocjančič wrote:
>>
>> Hi anyone know how I can transmitt PAL with sound and generate Teletext?
>>
>> I only know how to make simple FM Transmitter not TV one in GNU Radio
>>
>> So could anybody help me with building GNU Radio PAL with Sound transmitter
>>
>> you can transmitt ATSC, DVB-T2 but you can't transmitt Analog? (strange)
>>
>> Thanks for helping and Best regards
>>
>>
>>
>>
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>>
>>
>>
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>>

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