ATSC Transmitter

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drmpeg
Posts: 62
Joined: Fri Mar 01, 2013 3:58 am
Location: Silicon Valley
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Re: ATSC Transmitter

Post by drmpeg » Sat Feb 01, 2014 4:13 pm

ATSC signal from bladeRF on the spectrum analyzer.

Image

Ron

argilo
Posts: 6
Joined: Fri Mar 01, 2013 4:58 am

Re: ATSC Transmitter

Post by argilo » Sun Feb 02, 2014 7:51 am

I just added atsc-blade.py to my sdr-examples repository on Github:

https://github.com/argilo/sdr-examples

Also I made a few changes:

https://github.com/argilo/sdr-examples/ ... a58bf33e9c

I changed the transmit frequency to be in the 70cm amateur band, increased the output gain and replaced the three blocks I had been using for symbol coding (uchar to float -> multiply const -> add const) with a single "chunks to symbols" block.

argilo
Posts: 6
Joined: Fri Mar 01, 2013 4:58 am

Re: ATSC Transmitter

Post by argilo » Sun Feb 02, 2014 9:06 am

I also made a second version of the transmitter that works well on USB 2.0. It reduces the output sample rate down to 2/3 times the symbol rate so that less USB bandwidth is required.

https://github.com/argilo/sdr-examples/ ... de-usb2.py

argilo
Posts: 6
Joined: Fri Mar 01, 2013 4:58 am

Re: ATSC Transmitter

Post by argilo » Sun Feb 02, 2014 9:43 am

I've also eliminated two more unnecessary blocks, by having the "Chunks to Symbols" block output complex numbers:

https://github.com/argilo/sdr-examples/ ... f10f5c17ba

jowijo
Posts: 27
Joined: Sun Jan 05, 2014 9:50 pm
Location: Yakima, Washington

Re: ATSC Transmitter

Post by jowijo » Sat Apr 26, 2014 4:11 am

Managed to get live 1080i60 video and stereo sound OTA with the BladeRF. Complete with (semi) valid PSIP data and all. I wrote a horrible how-to here if you want to give it a shot. :D

unwiredben
Posts: 3
Joined: Tue May 27, 2014 3:33 pm

Re: ATSC Transmitter

Post by unwiredben » Mon Aug 11, 2014 1:48 pm

I've been using the combo of the BladeRF and this script to do ATSC testing on our Roku TVs now for several months. I had one question -- if I use this script with a transport stream that was originally captured as a low-bitrate subchannel, it looks like there's no padding inserted, so our TV plays the video at a high speed. Does anyone know of a good way to insert padding into the TS so it wll play at the proper speed? Doing it automatically as part of this script would be excellent.

unwiredben
Posts: 3
Joined: Tue May 27, 2014 3:33 pm

Re: ATSC Transmitter

Post by unwiredben » Tue Aug 12, 2014 8:01 am

A quick followup -- after some research, I finally found a tool that would pad the TS with null packets, TStoATSC from http://www-personal.umich.edu/~balazer/tstoatsc/. It only had a Windows executable, but it didn't take too much effort to port the command-line tool to unix, but it's still awkward to use. I think a better tool would be to update the GNU Radio ATSC module to include a "padWithNull" block that could be used on the TS input before going into the pad() block, and I might work on that in the near future.

N2TOH
Posts: 10
Joined: Tue Aug 12, 2014 10:18 am

Re: ATSC Transmitter

Post by N2TOH » Wed Aug 13, 2014 6:58 pm

TCP/IP encapsulation, what would it take to wrap internet traffic so it could be send along with a digital video transmission? perhaps as one of the sub channels along with actual video.

jowijo
Posts: 27
Joined: Sun Jan 05, 2014 9:50 pm
Location: Yakima, Washington

Re: ATSC Transmitter

Post by jowijo » Fri Aug 15, 2014 1:30 pm

Do you mean PSIP data? You can send a live TS with most PSIP tables using OpenCaster. I have some (old-ish) configurations here as nobody seems to have posted any online. With these, you can send EIT/ETT (EPG) tables, along with the basic TVCT/MGT/etc.

I've done tests with live video using ffmpeg at 480i, 720p60, 1080i, and 1080p24; with and without audio-only subchannels. Works very, very well.

Subchannels are designated by the TVCT, and PAT (Program Association Table). I have not uploaded a multi-channel configuration, as I am working on a web-based EPG/PSIP generator that will do all of the "hard work" for you. Once it's in working condition, it will be in the same git repo as the linked code.

N2TOH
Posts: 10
Joined: Tue Aug 12, 2014 10:18 am

Re: ATSC Transmitter

Post by N2TOH » Sat Aug 16, 2014 12:43 am

drmpeg, I see in your first post a listing for QAM modulations. has a transmitter been established for such modulations? I'm curious if they could be used for digital amateur radio television.

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