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Would this work for a handheld DVR?

Former Member

Hello All, I plan to develop a small handheld digital video recorder, and it looks like the Raspberry Pi might be just the piece of base-kit I've been looking for!

 

For the basic device, I need to connect an LCD touchscreen to it, which I would guess I can do via one of the USB ports, and a composite video (CVBS) input.  For future use, I'll need ADC and CAN-comms inputs, but that all looks fairly straight-forward, based on what I can see from the specs docs.

 

I was looking at the Beagleboard for this initially, but I hope to make small batch production runs with it for a business start-up.  The Beableboard people repeatedly say that it's not suitable for production runs, but don't say why unfortunately, so that's why I'm now pinning my hopes on the Raspberry Pi.

 

Can anyone out there help me out with these questions:...?

- From reading through the spec and some of the posts here, it looks like there is plenty of power to decompress a digital-video file and drive out a video stream to the HDMI or Video port, but what about the other way around - compressing a video input stream?  Is the MIPS of the ARM core and the available memory on the Raspberry Pi board enough to compress a video input stream (probably H.264), in readiness for storage to some kind of mass media (SD-Card, or possibly a USB SDD)?
- I see that there is something called a 'Camera Port' on-board, but can't find out much about it - is this suitable for composite video input, or is it for something else entirely?
- In case I can't connect a CVBS signal straight into the board, for a backup I've also been looking for a piece of hardware that I could use for digitising a CVBS input into a USB port, but the only one I've found that's even close to what I need costs a small fortune, and knocks my target price for six!  I want to get hold of somethig like those cheap bits of video=>PC conversion gadgets that are in abundance on eBay (etc), but that also allows integration into other systems.  Does anyone in the community know of such a thing for around £20?
- I want to use a touchscreen input to side-step the logistical complexity of having user-buttons read into the GPIO ports - is USB the only way I'm likely to be able to get a touchscreen input into the Raspberry Pi, or does anyone know of a device that would enable me to hook a touchscreen up to an interface that's already on the board?
- Lastly, is the Raspberry Pi suitable for what I want to do, or would I still be better off looking at the Beagleboard, or even Beaglebone?

 

The Raspberry Pi looks like a fantastic peice of equipment for this kind of thing - and it's British - and I'd love to be able to use it for my project, so any help or advice would be greatly appreciated.

 

Doug Ponsford.

Parents

  • Well, I agree with Michael Kellett, the RPI as is is unsuitable for what you want at the moment, but maybe its not because it lacks the hardware to do what you want, but more because there is no support at the moment for what you want to do with that hardware; let me explain.

     

    The RPi does have hardware (interfaces) for Video Input and LCD output, but there is no software support for them (yet), and the interfaces are very modern, and therefore may not be easy to interface to the kind of devices you want to use. It has these interfaces because the Broadcom SoC (chip) that is used is actually a chip meant for smartphones and tablets and such, and therefore naturally has these interfaces, (for smartphones and such) the RPF decided to bring them out to a connector for possible future use.

     

    For video input the RPI has a 15-pins connector on board for a CSI camera, this interface is meant for the type of camera's typically found in smartphones. It connects to such a camera module with a paper thin flexible foil (with metal traces on them). This interface thus provides a video input option, but perhaps not in a form that is directly useful to you. The foundation has announced they are working on a camera module for this interface.

    Its to be noted that this DSI camera "speaks" directly to the GPU, which can only be controlled through a software interface, so its hard to say what useful things you can do with the captured video, the (ARM) CPU is probably too slow to encode the video signal into any kind of video format, but the GPU might be able to, IF such a thing is supported by it, using the available software interfaces.

     

    Regarding an LCD, obviously you can hang a PAL (NTSC) or HDMI LCD screen on it using the RCA and HDMI connectors, but the SoC also has a DSI output connector (also a 15 pins connector of the same type as the DSI connector), which can be used to drive raw LCD panels. But for this interface too, hardly any documentation exists at the moment, nor does a driver. DSI is very powerful and can not only transfer video data to the panel, it also can control the LCD panel and read out a touch interface.

     

    So maybe sometime in the future something like you want will be possible, but not at the moment, and not unless you are very knowledgeable about these interfaces, and the software that is needed to make them work, and only then if you can coax the GPU to do what you want, which may be impossible without support from Broadcom.

  • in reply to mahjongg

    Martin,


    Looking at the spec, it does sound like all of the elements I am looking for are already 80-90% there, in terms of hardware alone, but it sounds like the support I would need to turn it into a product isn't quite there yet, at least on the software side.


    I have years of experience in embedded hardware and software development, so hardware mods wouldn't be an issue with this board, but I am brand-new to LINUX, so if there isn't already a fair bit of support for this board and the interfaces it already carries, or at least a BSP, then I should probably look elsewhere.


    I've already found suitable boards elsewhere, but these are mostly sourced from China, or Taiwan.  Not that there's a problem with Chinese or Taiwanese kit these days, it just would have been good to use some home-grown kit from the UK!


    I'll go back to my Taiwan boards for now, but I'll keep an eye on RaspberryPi developments and see if I can switch to it at a later date.


    Thanks for your comments - very helpful.

     

    Doug.

Reply
  • in reply to mahjongg

    Martin,


    Looking at the spec, it does sound like all of the elements I am looking for are already 80-90% there, in terms of hardware alone, but it sounds like the support I would need to turn it into a product isn't quite there yet, at least on the software side.


    I have years of experience in embedded hardware and software development, so hardware mods wouldn't be an issue with this board, but I am brand-new to LINUX, so if there isn't already a fair bit of support for this board and the interfaces it already carries, or at least a BSP, then I should probably look elsewhere.


    I've already found suitable boards elsewhere, but these are mostly sourced from China, or Taiwan.  Not that there's a problem with Chinese or Taiwanese kit these days, it just would have been good to use some home-grown kit from the UK!


    I'll go back to my Taiwan boards for now, but I'll keep an eye on RaspberryPi developments and see if I can switch to it at a later date.


    Thanks for your comments - very helpful.

     

    Doug.

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