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Mixing many USB web cams on the cheap for a robot drum machine

github.com

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Re: Mixing many USB web cams on the cheap for a robot drum machine

#11

Post by bayesianhorse »

pronoiac wrote: post #8
bayesianhorse wrote: post #5

I recently tried researching how to mix/record not so cheap cameras on a PC/Laptop/RasPi analogue. Remarkably tricky, because of the data rates involved. So far I have not seen a single affordable, open source compatible solution for "just" taking hdmi signals in. At least not for 1080p. I have modest hopes that such controllers might show up in the next years, maybe using USB 3 technology. There is also a Raspberry…

Was this the module you were looking at? http://www.auvidea.com/index.php/theme-styles/2013-06-22-21-... I'd heard the GPU was getting better docs, and I wondered if it would help handle this.

According to the site the board is already in production, but there is no further indication on when or where to buy. I don't think GPU docs will help enough. And then there's the issue of a completely new RPi2 SoC to consider...

Re: Mixing many USB web cams on the cheap for a robot drum machine

#12

Post by rasz_pl »

some things that made me sad when reading this github:

> One USB Host can theoretically take up to 127 client, but we found out only 1-2 Cameras per host controller work without glitches and missing frames.

and you didnt realize what is the real reason (not the limit of 7 bits address field in USB protocol)? No one bothered to do a simple calculation 640x480x2x30 per camera? :( btw USB 2.0 in reality is able to sustain ~40MB/s, hence 2 cameras at 30Hz max per controller = ~37MB/s.

>PCI can process less data then PCIExpress, so it is best to build your system on PCIe cards

PCI is ~130MB/s, plenty for 6 cameras, again no numbers

Of course you could simply find cheap cameras with building mjpeg compression and avoid adding external usb controller cards - Great source for cheap camera modules is laptop service parts. For the last 10 years USB webcams have been standard in laptops. Example ebay auction

http://www.ebay.com/itm/Macbook-iSight-Camera-replacement-fo...

ISight supports:

MJPEG 640×480 @ up to 60fps

MJPEG 720×480 @ up to 60fps

MJPEG 800×600 @ up to 30fps

MJPEG 1024×576 @ up to 30fps

etc ...

and all of a sudden we have <3MB/s per $3 camera.

Re: Mixing many USB web cams on the cheap for a robot drum machine

#13

Post by rasz_pl »

bayesianhorse wrote: post #5

I recently tried researching how to mix/record not so cheap cameras on a PC/Laptop/RasPi analogue. Remarkably tricky, because of the data rates involved. So far I have not seen a single affordable, open source compatible solution for "just" taking hdmi signals in. At least not for 1080p. I have modest hopes that such controllers might show up in the next years, maybe using USB 3 technology. There is also a Raspberry…

define cheap?

Those guys are working on hdmi-to-parallel CSI input converter for Olimex A10/A20 Linux SBCs

https://videobrick.wordpress.com/

Then there is this guy cooking hdmi-to-mipi CSI for the Pee

http://theiopage.blogspot.com/

then you have chinese HDMI over Ethernet extenders (~$75 free shipping), they compress 1080 to mjpeg, you can throw away receiver and just slurp that data into your computer

https://hdmiextender.codeplex.com/

1080i hdmi pcie capture cards start at $40, $50 for 1080p with borders (not 1:1), $65 Trident chipset proper 1080p grabbers

Re: Mixing many USB web cams on the cheap for a robot drum machine

#14

Post by rasz_pl »

pronoiac wrote: post #8
bayesianhorse wrote: post #5

I recently tried researching how to mix/record not so cheap cameras on a PC/Laptop/RasPi analogue. Remarkably tricky, because of the data rates involved. So far I have not seen a single affordable, open source compatible solution for "just" taking hdmi signals in. At least not for 1080p. I have modest hopes that such controllers might show up in the next years, maybe using USB 3 technology. There is also a Raspberry…

Was this the module you were looking at? http://www.auvidea.com/index.php/theme-styles/2013-06-22-21-... I'd heard the GPU was getting better docs, and I wondered if it would help handle this.

From the writup on this page it seems Pee camera module works in RAW mode. This is weird and uncommon.

Re: Mixing many USB web cams on the cheap for a robot drum machine

#15

Post by rasz_pl »

bayesianhorse wrote: post #11
pronoiac wrote: post #8

Earlier quoted context omitted.

Was this the module you were looking at? http://www.auvidea.com/index.php/theme-styles/2013-06-22-21-... I'd heard the GPU was getting better docs, and I wondered if it would help handle this.

According to the site the board is already in production, but there is no further indication on when or where to buy. I don't think GPU docs will help enough. And then there's the issue of a completely new RPi2 SoC to consider...

Gpu docs wont, but videocore docs would, sadly Broadcom is hostile and will most likely never release low level stuff, same goes for mipi dsi LCD interface.

Pee2 uses same videocore, only difference is CPU IP.

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