Idea: Wirelessly broadcast the screen to a smartphone via bluetooth

mrisgame99

A smartphone as a Raspberry monitor:
Broadcast the screen to a smartphone via bluetooth:

Start an Android or iPhone App (maybe there is something already done).
Pair both devices with a PIN or similar in an easy way (as a final user, no SSH).
Finally you have your mobile as the screen (only the screen not the controls).

So you can play anywhere, everybody is carrying a smartphone, even if you don't have access to a big monitor.

Any idea for such development? Also it is required an Android/iPhone app.

AlexMurphy

@mrisgame99 This is already a thing called VNC. I doesn't work with RetroPie because it uses a windowed environment, RetroPie does not, instead using SDL2. Even if you could make it work it would be useless for gaming due to latency and lag. Sorry to crap on your dream!

mrisgame99

ok thank you. I don't know what is behind each system and how they work, but for example you can send a lot of data via the usb to the mobile, then you have to translate that to the screen image...

zettea

OK just a quick thought......bluetooth has a transfer limit of 25mb/s....
and 1920 x 1080 has 6220800 (2073600 rgb sets) pixels at 32 bits of color at 30 or 60 frames a second

No compression
1920x1080 60fps 32bit_color : 3981312000 bytes/second or 3981.2 mb/s

25mb/3981.2mb=~1/160

So video alone from the Raspberry Pi at a standard quality is already 159.2 times higher than the maximum bluetooth bandwidth. What compression method can reliably in under 10 milliseconds compress something 200-250 time to cram that down a short radio antenna. Also this sounds like a fire hazard.

Maybe try Wifi-Direct dongle systems, that has a cap of up 250mb/s...

obsidianspider

Don't forget that the Pi is limited to USB 2 speeds, and that kind of throughput would put a big load on the SOC

zettea

@obsidianspider I have read up on typical RPi3 BT speeds and they shape up to be maximum 256kb/s

Meaning that the BT Display would be 15551.5625 the maximum capability at best..... The compression would need to be 20,000x in under 10 milliseconds. That kind of compression would take hours to years for a Pi, and the entire screen would be an artifact.