SSTV with the Prop works!
leggs
Posts: 21
Last holiday I managed to modify the Bell202 object to transmit APRS packets.
I am on holiday again, and now I am working on SSTV. Using the Bell202 object as a starting point, I wrote a program to send 80x256 images using Martin 2. At the moment the images are in 3bit monochrome, but this is not a speed limitation, more of a space limitation on the Prop. Upgrading to colour would be easy. I am planning on interfacing it to one of the composite video capture objects. Either Phil's, or the one from PropPixelator.
If there is any interest, I will clean up my code and post some source code soon!
I am on holiday again, and now I am working on SSTV. Using the Bell202 object as a starting point, I wrote a program to send 80x256 images using Martin 2. At the moment the images are in 3bit monochrome, but this is not a speed limitation, more of a space limitation on the Prop. Upgrading to colour would be easy. I am planning on interfacing it to one of the composite video capture objects. Either Phil's, or the one from PropPixelator.
If there is any interest, I will clean up my code and post some source code soon!
Comments
73 de
DL7PNP
As for image capture. My PropPixelator captures great B/W video and audio, still studying Phil's color code. It is quite slow but good for stills.
Keep up the good work!
Perry
I have interfaced your PropPixelator frame grabber to my SSTV encoder. I can successfully transmit 64x120 frames using Robot8 mode. However, Robot8 mode has a maximum resolution of 160x120. Is it possible to modify your frame grabber to capture a few more horizontal pixels? I have tried and failed, as I do not understand to intricate timings involved with ADC conversion.
When you have some time, could you maybe post a version of your frame grabber that works at 5bit, or even 4bit resolution, but with more horizontal pixels?
Thanks!
Great work. The last time I played with a slow scan TV I had a home brew interface for the Commodore 64. It's been a while. LOL
I am trying to upgrade the "Pixelator" to color capture and making good progress. The secret to getting more pixels is using a higher speed clock or reducing the sample time. . Presently I am getting 92x120 with a clock frequency of 108Mhz (13.5Mhz) crystal. The horizontal limit in this case has to do with the color logic. At 80Mhz I can only get 72 pixel lines, also because of my NTSC_16bpp driver.
If one uses only greyscale it should be possible to get close to 128 pixel lines.
I noticed quite a bit of improvement in the captured images when going from 64 to 80 pixels per line.
Finally If you reduce the the sample time for each pixel you can get more pixels but less shades per pixel. This is what you want if you only desire 4 bits per pixel. The main problem is adjusting the black level so that the display becomes visually acceptable.
Perry
Curious if you ever got this into a working state, or if you released the code to this anywhere? In the past few months, I've gotten into sdr on Linux (rtl-sdr) and SSTV, APT, etc since yesterday (reception wasn't good enough to see a picture, but I heard my first NOAA-15 and NOAA-18 APT transmissions yesterday as they went overhead - quite exciting). I'd love to see more modems for the prop. It was neat to see the Bell 202 object work with minimodem on the PC side, even if it was wired
Cheers,
Jesse
(formerly KA1VTK)