Low SR

G4KLB
Posts: 196
Joined: Wed May 28, 2008 10:46 am

Low SR

Postby G4KLB » Tue Dec 09, 2014 4:55 pm

Digilite config can be set to low symbol rates very easily, but I am trying to work how to set WinTV6 or GBPVR to less than 1500, looking to try 1.133Ms/s for a test.

The plan is to write some SD cards with different SR and FECs for quick tests on the bench.

Since running WinTV6 with the fix I've not had to edit anything for a long time! :oops:

M0DTS
Posts: 326
Joined: Sun Feb 24, 2008 9:03 pm
Location: Yarm
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Re: Low SR

Postby M0DTS » Tue Dec 09, 2014 6:48 pm

MPEG2 at low SR <1000 with the pvr units is not easily done, the audio takes up 192kbps and the minimum video bitrate is 500kbps....
at 500Ks and 7/8 fec the data rate including Transport Stream encapsulation must be 806kbps... not sure it can be done but i admit i have not tried yet!
Picture quality will be horrible with mpeg2, you could use the raspberry pi to stream the camera on udp into digilite to get low bitrate mpeg4.

Rob

G4KLB
Posts: 196
Joined: Wed May 28, 2008 10:46 am

Re: Low SR

Postby G4KLB » Wed Dec 10, 2014 1:32 am

Thanks for the info Rob,
I will see what 1.133Ms/S looks like when I remember how to set WinTV6 or GBPVR to the correct settings, I know the video bit rate needs to be 1110 for FEC 3/4, also have set the audio as low as it will go. Will also try it with no Audio to see what that looks like.

For SR<1000 H264 is the best option, RP into Digilite modulator works well,( no audio though ) so will be testing that with the set of nyquist filters I have just built.
So many bands to build gear for! 8-)

G4EWJ
Posts: 587
Joined: Wed Feb 17, 2010 10:11 am
Location: Wirral

Re: Low SR

Postby G4EWJ » Wed Dec 10, 2014 12:45 pm

With DigiLite v2.50, you can omit the audio from the transport stream. In DigiLite Config, click OTHER, then AUDIO and then tick the NO AUDIO box that appears below EPG Info. The Video bit rate field should change to reflect the new TS capacity.

I'll post a separate note for SD card operation at low SR settings.

Brian

M0DTS
Posts: 326
Joined: Sun Feb 24, 2008 9:03 pm
Location: Yarm
Contact:

Re: Low SR

Postby M0DTS » Wed Dec 10, 2014 6:42 pm

oh yes forgot about the selectable audio channel, long time since i used the windows DigiLite Software ;-)

Rob

G4KLB
Posts: 196
Joined: Wed May 28, 2008 10:46 am

Re: Low SR

Postby G4KLB » Wed Dec 10, 2014 11:48 pm

Thanks Brian, I had found the tick box to have no audio and noted the change in video bit rate, as well as user defined SR,
look forward to the SD card write up, very handy to use portable to get up and running quickly.


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