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I was wondering about the best way to transmit a real-time video (wireless).I do not need to be high quality video, so I've bought this camera module:

Camera module Camera datasheet

Now I need to make a wireless transmission in real time without substantial delay. I have here a couple of nrf24l01 modules:

NRF24L01 NRF24L01 Datasheet

Note that despite the fact that it uses a carrier of 2.4GHz, it has a maximum air data rate of only 2Mbps. Is this only because all the checksum, encoding and redundance methdos (specified in datasheet) to ensure a reliable communication?

If that so, I know that for a video live streaming I should use some type of transmission that excels for speed and not for reliability, correct? So this module will probably be a bad choice.

With that said, now I still wonder what should be the best method: analog or digital? I've seen some 5.8GHz analog transmitters but its input is an analog video signal. Since my camera module only outputs digital signal, I would have to use a DAC between the camera and this 5.8GHz module, correct? On the other hand, I could use some other kind of 2.4GHz transceiver which could give me some free choice of encoding. Then I could use some simple digital modulating process (FSK based) and transmit full RGB scenes with a simple CRC in the end.

Still, another thing I thought is to compress each image before sending (with some high speed MCU that I've got here). The problem is that my best MCU has only 8kB of RAM and I think it would easily exceed that.

What do you suggest me to use in this process?

Just a reminder: I need a fast transmission because my computer (receiving images) will compute some algorithms based on those images to send back a command to my MCU. So it all depends on this transmission.

Felipe_Ribas
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    The nRF module has a data rate of 2Mbps because it's using 2MHz of radio bandwidth and GFSK modulation. I'd suggest looking for an existing analog radio solution. – pjc50 Nov 28 '13 at 16:29
  • What does that implies? I thought that since it's a 2.4GHz carrier, it should have a bit rate near the 2Gb/s. Since it has its corrections and redundance methods to provide a reliable comunication, the payload should be something lower than that. But 2Mbps is pretty much lower than 2.4GHz... and also, you suggest me to use a DAC to output a analog video signal and then transmit with a analog radio solution? – Felipe_Ribas Nov 28 '13 at 20:36
  • Radio bandwidth is basically (top frequency used) - (bottom frequency used). Achievable data rate for that scheme depends on modulation used, but this is essentially why WiFi data rate (also in the 2.4GHz band) is currently maximum ~100mbit. (This explanation has been greatly simplified to fit in the comment box) – pjc50 Nov 29 '13 at 13:05
  • Existing analog solution: this kind of thing http://www.espow.com/product_info.php?products_id=2671&currency=GBP&gsc=googleshopping&gclid=CNuAhfaHirsCFeTLtAodfAEAEw (doesn't specify, but it looks like it transmits composite video in the 2.4GHz band) – pjc50 Nov 29 '13 at 13:07
  • Do you think compressing the image and sending it through digital comunication is much worse than an analog solution like this one? Another thing: since data rate varies a lot due to modulation used, can't I use a digital transmitter/receiver with high data rates? What would be the best modulating processes to do that? – Felipe_Ribas Nov 29 '13 at 18:15
  • Digital compression / encoding will always add latency, usually a minimum of one video frame, analogue can be almost instantaneous. Obviously digital can have other advantages. – John U Feb 26 '14 at 10:38

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You could split data rate into two halves and use two separate Nordic modules for transmission and two separate modules for reception. Each pair can be set to transmit and receive on different channels.

It's not elegant but it halves the problem. I bet it would work with several pairs. Just a thought.

Andy aka
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  • Why do you think is this better than making an analog transmitting or a less reliable digital transmission? And do you know what is the reason for a low air data rate even with a 2.4GHz carrier? – Felipe_Ribas Nov 28 '13 at 14:25
  • @user2110874 I'm guessing the 2Mbps limit payload data rate allows more "parallel" channels to co-exist simultaneously. Lower data rates = more receiver sensitivity = bigger transmission distances too. I'm offering this answer because it is doable with existing (and fairly cheap) hardware. – Andy aka Nov 28 '13 at 16:53
  • Isn't there any other suggestion not too much expensive that could provide me a better result? – Felipe_Ribas Nov 28 '13 at 20:37
  • I'm wondering what makes an inexpensive better result. – Andy aka Nov 28 '13 at 20:51
  • I can't compress each whole frame before sending it because of RAM size. Maybe compressing each group of, let's say, 5 lines of the frame and send it should be a good idea? – Felipe_Ribas Nov 29 '13 at 18:16
  • Video compression is not my field. If you think you can do that then it's def gonna save bandwidth. – Andy aka Nov 29 '13 at 19:57
  • A small, 8KB RAM MCU is the wrong tool for the job. In order to get anywhere near 2Mbps data rates, you will have to either reduce the resolution, frame rate, lossy compress or all of the above. Consider a non compressed, full resolution color NTSC signal's data rate is ~240Mbps. – Lior Bilia Apr 27 '14 at 11:12