A+ Capabilities

[microMinded]

Quick questions:

- Can the Model A+ run the 320x480 Touch LCD? My A13 Olinuxino had 256MB ram and it could barely run X and nothing else...

- Can the A+ Run the camera at full resolution, 5MP images and 1080P streaming?

- Can the Pi run Stellarium? If not are there any alternatives?

[ghans]

2) Yes , because Hardware acceleration. Note that you cannot
do take video and stills at the same time. You need to
switch between modes (and back) and that can take a second.

ghans

[jamesh]

Stellarium, when I tried it, was very very slow. But I failed to get HW acceleration working (I think). It may be better if enabled, but it may be just as bad, depending on where the bottlenecks are. This was a couple of years ago - perhaps someone else has figured it out.

[mikerr]

Note that you cannot
do take video and stills at the same time. You need to
switch between modes (and back) and that can take a second.

picamera can take video and stills at the same time by using the video port
http://picamera.readthedocs.org/en/late ... -recording

[microMinded]

picamera can take video and stills at the same time by using the video port
http://picamera.readthedocs.org/en/late ... -recording

That's a pretty nifty trick! it's even able to capture at two different resolutions. Is this a feature of the API or a capability built into the imaging sensor?

[ghans]

picamera uses the MMAL C API , which itself is built on
the OpenMAX IL C API. The talk about "components" and
"ports" is OpenMAX lingo , so i guess it is a API feature
exposed in a more comfortable way.

ghans

[microMinded]

6.3. The preview doesn’t work on my PiTFT screen
The camera’s preview system directly overlays the Pi’s output on the HDMI or composite video ports. At this time, it will not operate with GPIO-driven displays like the PiTFT.

I assume this means there will be no preview across a VNC connection? Or does VNC copy/compress and stream the video buffer directly?

[ghans]

Thats right , VNC cannot display the camera preview either.


ghans

[microMinded]

Well that throws a wrench into the plans as I was originally going to use an SPI LCD or VNC...

Do you know if the cameras output is being transferred DMA style directly to the GPU's internal memory or if its being written to a memory mapped location?

If its a MMAP block transfer I could theoretically copy the data from the same memory location into a false dev device. If its directly into GPU memory then I would need to setup a circular buffer the size of the the YUV full frame and constantly record video and then access that block device.

Anybody done work that that yet?

[ghans]

Well , there is a workaround :
https://github.com/notro/fbtft/wiki/Fra ... -mirroring

ghans

[jamesh]

Well that throws a wrench into the plans as I was originally going to use an SPI LCD or VNC...

Do you know if the cameras output is being transferred DMA style directly to the GPU's internal memory or if its being written to a memory mapped location?

If its a MMAP block transfer I could theoretically copy the data from the same memory location into a false dev device. If its directly into GPU memory then I would need to setup a circular buffer the size of the the YUV full frame and constantly record video and then access that block device.

Anybody done work that that yet?

It's all done on the GPU, the camera ISP is composited in real time by the HVS hardware block. It's the only way it can be done fast enough. Moving data to and from the ARM at that speed isn't possible at full frame rate.

[microMinded]

Well , there is a workaround :

Interesting framebuffer mirroring but the preview only exists in silicon so it wont help this case.

It's all done on the GPU, the camera ISP is composited in real time by the HVS hardware block. It's the only way it can be done fast enough. Moving data to and from the ARM at that speed isn't possible at full frame rate.

Guess i'm going to look into my ring buffer idea then.

[ghans]

fbcp should work for the camera preview , it works with
most other programs which use GPU accelaration by using
a Pi-specific API to grab screenshots.

ghans

[DirkS]

fbcp should work for the camera preview

It does.

[microMinded]

fbcp ... Pi-specific API to grab screenshots.

I didn't get that from a cursory read over of the page, but I am glad it does. I will look at its code on how it is grabbing the camera preview as if its all done in silicon their should be no possible way to read it. Their might be a memory map hidden in there somewhere.

But for 2% CPU loss for a full framebuffer copy why reinvent the wheel, lol.