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Electronics => Projects, Designs, and Technical Stuff => Topic started by: HSPalm on January 26, 2016, 04:04:14 pm

Title: Wireless multicast VGA video, digitally. Get me on the track?
Post by: HSPalm on January 26, 2016, 04:04:14 pm

Hi guys,
Just want to discuss various methods for streaming video digitally, what I can expect of quality, latency and what not.

You may already see that I'm interested in tackling the interference problems that occur when several people fly FPV together on adjacent channels. The problems we encounter today are mostly related to noise from environment and other pilots chiming in on your video feed, not from signal loss from your own transmitter. I want the video digital to block out others, not to improve one pilots own signals.

So, feel free to smack me down to ground if I'm thinking terribly wrong here.

My "requirements" (or dream scenario) is
- Quality as good as or close to PAL/NTSC or VGA resolutions.
- 25 fps
- Low latency, less than 50ms
- Overhead in bandwidth to accomplish CRC checking.
- Don't want or need error correction of lost packets

I understand I may have to do with greyscale video, but to me this is not bad as a start at least. All though, color->greyscale conversion adds to the processing task so it might introduce latency.
What is the greatest obstacle to tackle? I understand video must be compressed, how? Wifi can do it, even with 4K video, what tasks are run on each sides of this link that adds to latency that I might do without?

I'm not used to thinking of high data rates, bandwidth and lots of data, so much of this stuff confuses me. So I googled, and found this page: http://www.excitingip.com/2722/bandwidth-considerations-for-ip-surveillance-cameras-how-to-reduce-the-bandwidth-occupied-by-them/ (http://www.excitingip.com/2722/bandwidth-considerations-for-ip-surveillance-cameras-how-to-reduce-the-bandwidth-occupied-by-them/)

Quote

Type: VGA Resolution

5 frames per second – 256 Kbps to 750 Kbps
8 frames per second – 384 Kbps to 1 Mbps
10 frames per second – 500 Kbps to 1.2 Mbps
15 frames per second – 750 Kbps to 1.2 Mbps
30 frames per second – 1 Mbps to 1.5 Mbps

So if this is right, VGA video will (with some kind of compression) require at least 1Mbps. So does that mean the "only thing" I have to look for now is a way to digitize composite video, compress it, and put it out over a wireless link that supports the data rates I need?

I found this radio chip from ON Semiconductor that claims higher datarates than most others, http://www.axsem.com/www/rfics/general-purpose/ax5031 (http://AX5031). The claim is 2000kbps, or 2Mbps.
And at this point I invite you to believe that I'm not as unfamiliar with electronics as it might seem, my daytime job is beeing a hardware developer in M2M radio applications. It's just video and huge data that confuses the hell out of me.

So, what is wrong with the picture below? Is it achievable?
(https://lh3.googleusercontent.com/_UQCxTYXXD6wqzFZUvBtCV-Ac6NDVOWhmwIpKXVaouhMigP5bHbQxXCvC-oGoUQD3innlOwQtLPdv1eUXnJifUJcx8G4O1ap21agtCM3s1uqXZt6ydECsBF8lfwWARmeGhsR7Bg6xs6STAF9588lb4E7UpFqKkkfd34T2ZLpzDMeBXtYYWTYRWgwhlL-4p0FaBnObIPsfXWTkI2RsGv34tGe7WFbkxv9MgB5nswkguT8LwM52SpqiE7Th7yMbK_lqzfebAmltRwn1ikC3JmXIYRw5xTE44hxwm3dkFh4PQS4s7mIfQGIxwQkA91xq_bOJOjpYjqxDrkeaKvHoSXsDl8N84EO2R29s-U_dwSJpNXzqbMREQLJxgD-WkO_QHGW0Nuk_VfijShPCebCJL3epETSMk7Pph_VSDu3sEnkrViHS1DKmzBtko8g7CiuBFk6nOjYTGV93s_6pOF5HaZScDkcGwt03ejk6xRH5ILIkGmizpjmDx8ASqrGB4SILARlKOmV7YE-R-NPw-uLWGYmBhOvpzkm4m0wkm_IKnsQv7iUcjMLIRFcae5_UKo2YrqA8pbnGw=w1060-h460-no)